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Human ovarian ageing encompasses the age-related decline in female fertility. Oxidative stress and mitochondrial dysfunction in oocytes are suggested as causal, but corroborating evidence is limited. Using immunofluorescence imaging on human ovarian tissue, we found oxidative damage by protein and lipid (per)oxidation at the primordial follicle stage. Additionally, using comprehensive metabolomics and lipidomics, a cohort of 150 human germinal vesicles and metaphase I oocytes and 15 corresponding cumulus cell samples displayed a shift in glutathione to oxiglutathione ratio and depletion of phospholipids. Age-related changes in polar metabolites suggested a decrease in mitochondrial function, as demonstrated by NAD+, purine and pyrimidine depletion, while glycolysis substrates and glutamine accumulated with age. Oocytes of advanced maternal age likely used alternative energy sources like glycolysis and the adenosine salvage pathway, and possibly increased ATP production in cumulus cells. These findings indicate that oocytes of advanced maternal age suffer from oxidative damage and mitochondrial dysfunction.Graphical abstract

The introduction of in vitro fertilization (IVF) into the routine practice of reproductive medicine opened the gateway for exciting new innovations. Moreover, the accessibility of human embryos before uterine transfer made it possible to secure biopsy material for genetic analysis. In 1990, it was first reported that a procedure currently known as preimplantation genetic diagnosis was used in the genetic selection of diseasefree embryos.1 The goal of this procedure is to assist couples who are at known risk for transmitting a genetic disease in conceiving an unaffected child. However, as is often the case with the introduction of a new technology, preimplantation genetic diagnosis was soon deployed for indications other than those for which it had originally been intended. In this case, the added indication was to increase the IVF success rate (pregnancy per embryo transfer) by determining the ploidy status of the embryo.

STUDY QUESTION How do high-quality human preimplantation embryos influence the endometrium to promote their own implantation? SUMMARY ANSWER High-quality human preimplantation embryos secrete a specific microRNA (miRNA), hsa-miR-320a, which promotes migration of human endometrial stromal cells (hESCs). WHAT IS KNOWN ALREADY We have previously shown that high-quality human preimplantation embryos excrete unknown factors that influence migration of hESCs. STUDY DESIGN, SIZE, DURATION Embryo excreted miRNAs, specifically those excreted by high-quality embryos, were identified and their effect on hESCs was determined by measuring the migration capacity and gene expression patterns of primary isolated hESCs. PARTICIPANTS/MATERIALS, SETTING, METHODS Embryo conditioned medium (ECM) from routine ICSI procedures was used to identify embryo excreted miRNAs. miRNome analyses were performed on ECM from individually cultured embryos with high morphological quality, with low morphological quality or empty control medium. MiRNA mimics and inhibitors were then used to further study the effect of miRNAs of interest on migration and gene expression of hESCs. Migration assays were performed using hESCs that were obtained from endometrial biopsies performed on hysterectomy specimens from women that received surgery for spotting due to a niche in a cesarean section scar. MAIN RESULTS AND THE ROLE OF CHANCE By using miRNA mimics and inhibitors, we showed that hsa-miR-320a alone can stimulate migration of decidualized hESCs, accurately resembling the response typically triggered only by high-quality embryos. Transcriptome analysis further demonstrated that this effect is very likely mediated via altered expression of genes involved in cell adhesion and cytoskeleton organization. LIMITATIONS, REASONS FOR CAUTION The effect of hsa-miR-320a on hESCs was measured in vitro. Further studies on the in vivo effect of hsa-miR-320a are warranted. WIDER IMPLICATIONS OF THE FINDINGS Implantation failure is one of the major success limiting factors in human reproduction. By secreting hsa-miR-320a, high-quality human preimplantation embryos directly influence hESCs, most likely to prime the endometrium at the implantation site for successful implantation. Together, our results indicate that hsa-miR-320a may be a promising target to further increase success rates in assisted reproduction. STUDY FUNDING/COMPETING INTEREST(S) The study was funded by the Amsterdam University Medical Centers and the Amsterdam Reproduction & Development Research Institute. R.P.B., G.H. and S.M. have a patent on the use of hsa-miR-320a in assisted reproduction treatments pending. TRIAL REGISTRATION NUMBER N/A.

Many clinics offer routine genetic testing of pregnancy loss tissue. This review presents a comprehensive literature search and meta-analysis on chromosomal abnormality rates of pregnancy loss tissue from women with a single or recurrent pregnancy loss. A total of 55 studies published since 2000 were included, analysed on the prevalence of test failure rates, abnormality detection rates and percentages of trisomy, monosomy X, structural abnormalities and other clinically (ir)relevant abnormalities detected by conventional karyotyping, array-comparative genomic hybridization (aCGH), single nucleotide polymorphism (SNP) array, fluorescence in-situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA). The detected prevalence of chromosomal abnormalities was 48% (95% confidence interval [CI] 39–57) using aCGH, 38% (95% CI 28–49) with FISH, 25% (95% CI 12–42) using MLPA, 60% (95% CI 58–63) using SNP array and 47% (95% CI 43–51) with conventional karyotyping. The percentage of detected abnormalities did not differ between women that suffered sporadic (46%; 95% CI 39–53) or recurrent (46%; 95% CI 39–52) pregnancy loss. In view of the high prevalence of chromosomal abnormalities in pregnancy loss tissue, and the low chance of recurrence of the same chromosomal aberration, it was concluded that detection of specific chromosomal abnormalities in pregnancy loss tissue has no clinical benefit. Therefore, routine testing of pregnancy loss tissue for chromosomal abnormalities is not recommended.

The field of reproductive medicine has been criticized for introducing ARTs without systematic research on possible safety risks and for failing to meet the standards of evidence-based innovation held elsewhere in medicine. In this paper, firstly, we ask whether ‘responsible innovation’ has been a concern for the field, and if so, how it has understood the practical implications of this idea for the development and introduction of potentially risky new ARTs. Secondly, we consider whether the field has indeed fallen short of its responsibilities in this respect, and if so, how things can be improved. To answer these questions, we present three case studies involving the introduction of a new reproductive technology: ICSI, preimplantation genetic testing and mitochondrial replacement therapy. As a framework for analyzing these cases, we used Per Sandin’s account of the four dimensions of dealing with risks (threat, uncertainty, action, command) that are central to debates about the possible role of the so-called precautionary principle. We conclude that, although offspring safety concerns have been on the agenda of the debate about bringing the relevant technologies to the clinic, systematic safety and effectiveness studies were not always conducted. As professionals in assisted reproduction have a responsibility to take account of the welfare of the children they are creating, we suggest a policy of proceeding with systematic caution. Legal measures may be needed to ensure that professional guidance is followed in practice. Finally, an open question concerns the threshold for acceptable risk in the context of introducing new ARTs. Multiple stakeholders, including professional societies and patient organizations, should have a role in the urgent debate about this.

The conclusion of the Human Fertilisation and Embryology Authority that ‘add-on’ therapies in IVF are not supported by high-quality evidence has prompted new questions regarding the role of the randomized controlled trial (RCT) in evaluating infertility treatments. Critics argue that trials are cumbersome tools that provide irrelevant answers. Instead, they argue that greater emphasis should be placed on large observational databases, which can be analysed using powerful algorithms to determine which treatments work and for whom. Although the validity of these arguments rests upon the sciences of statistics and epidemiology, the discussion to date has largely been conducted without reference to these fields. We aim to remedy this omission, by evaluating the arguments against RCTs in IVF from a primarily methodological perspective. We suggest that, while criticism of the status quo is warranted, a retreat from RCTs is more likely to make things worse for patients and clinicians.

STUDY QUESTION What is the composition and stability during storage and culture of fifteen commercially available human preimplantation embryo culture media? SUMMARY ANSWER No two culture media had the same composition, and both storage and culture had an effect on the concentrations of multiple components. WHAT IS KNOWN ALREADY The choice of embryo culture medium not only affects the success rate of an IVF treatment, but also affects the health of the future child. Exact formulations of embryo culture media are often not disclosed by manufacturers. It is unknown whether the composition of these media changes during storage or culture in the IVF laboratory. Without details on the exact concentrations, it is not possible to determine which components might be responsible for the differences in IVF success rates and health of the resulting children. STUDY DESIGN, SIZE, DURATION Between October 2014 and October 2015, all complete human preimplantation embryo culture media, i.e. ready to use for IVF, that were commercially available at that time, were included (n = 15). Osmolality and the concentration of thirty seven components including basic elements, metabolites, immunoglobulins, albumin, proteins and 21 amino acids were tested immediately upon arrival into the IVF laboratory, after three days of culture without embryos (sham culture) starting from the day of arrival, just before the expiry date, and after three days of sham culture just before the expiry date. PARTICIPANTS/MATERIALS, SETTING, METHODS Ions, glucose, immunoglobulins, albumin and the total amount of proteins were quantified using a combination of ion selective electrodes and photometric analysis modules, and lactate, pyruvate and 21 amino acids were analysed by ultra performance liquid chromatography mass spectrometry. Osmolality was analysed by an advanced micro-osmometer. Statistical analysis was done using multivariate general linear models. MAIN RESULTS AND THE ROLE OF CHANCE The composition varied between media, no two media had the same concentration of components. Storage led to significant changes in 17 of the 37 analyzed components (magnesium, chloride, phosphate, albumin, total amount of proteins, tyrosine, tryptophan, alanine, methionine, glycine, leucine, glutamine, asparagine, arginine, serine, proline, and threonine). Storage affected the osmolality in 3 of the 15 media, but for all media combined this effect was not significant (p = 0.08). Sham culture of the analyzed media had a significant effect on the concentrations of 13 of the 37 analyzed components (calcium, phosphate, albumin, total amount of proteins, tyrosine, alanine, methionine, glycine, leucine, asparagine, arginine, proline, and histidine). Sham culture significantly affected the osmolality of the analysed culture media. Two media contained 50% D-lactate, which a toxic dead-end metabolite. In a secondary analysis we detected human liver enzymes in more than half of the complete culture media. LIMITATIONS, REASONS FOR CAUTION The analyzed culture media could contain components that are not among the 37 components that were analyzed in this study. The clinical relevance of the varying concentrations is yet to be determined. WIDER IMPLICATIONS OF THE FINDINGS The presence of D-lactate could be avoided and the finding of human liver enzymes was surprising. The wide variation between culture media shows that the optimal composition is still unknown. This warrants further research as the importance of embryo culture media on the efficacy and safety in IVF is evident. Companies are urged to fully disclose the composition of their culture media, and provide clinical evidence supporting the composition or future changes thereof. STUDY FUNDING/COMPETING INTEREST(S) None.

STUDY QUESTION Are genes known to be involved in somatic cell ageing, particularly related to longevity pathways, associated with the accelerated ageing process of the ovary? SUMMARY ANSWER Growth, metabolism, and cell-cycle progression-related pathways that are involved in somatic cell ageing are also associated with ovarian ageing. WHAT IS KNOWN ALREADY Ovarian ageing is characterized by a gradual decline in ovarian follicle quantity, a decline in oocyte quality, and lower chances of pregnancy. Genetic pathways modulating the rate of somatic cell ageing have been researched intensively. Ovarian ageing does not follow the same timeline as somatic cell ageing, as signs of ovarian ageing occur at a younger female age, while the somatic cells are still relatively young. It is not known whether the generally recognized somatic cell longevity genes also play a role during ovarian ageing. Looking at somatic cell longevity genes can lead to new hypotheses and possible treatment options for subfertility caused by ovarian ageing. STUDY DESIGN, SIZE, DURATION In this observational study, we analysed a dataset of individual gene expression profiles of 38 germinal vesicle (GV) oocytes from 38 women aged between 25 and 43 years. We correlated female age (calendar age in years) and biological age (factors known to be associated with ovarian ageing such as dosage of FSH needed for ovarian hyperstimulation, and antral follicle count (AFC)) with gene expression signatures of longevity pathways. PARTICIPANTS/MATERIALS, SETTING, METHODS Transcripts of 38 GV oocytes were used for individual gene expression analysis. R version 3.5.1 was used to process and analyse data. The GeneAge database (build 19) was used to obtain mouse ageing-related genes. Human to mouse orthologues were obtained using the R package biomaRt. Correlations and significance between gene expression data and age were tested for using Pearson's product moment correlation coefficient using ranked expression data. Distributions were compared with an ANOVA, and the Tukey Honest Significant Difference method was used to control for the Type I error rate across multiple comparisons. MAIN RESULTS AND THE ROLE OF CHANCE Of the 136 genes in the GeneAge database, the expression of 15 anti-longevity genes identified in oocytes showed a positive correlation with female calendar age and FSH dosage administered during ICSI treatment, and a negative correlation with AFC. Expression of 32 pro-longevity genes was negatively correlated with calendar age and FSH dosage, and positively correlated with AFC. In general, anti- and pro-longevity genes changed in opposing directions with advancing maternal age in oocytes. Notably, the anti-longevity genes include many ‘growth’-related genes involved in the mechanistic target of rapamycin (mTOR) Complex 1 pathway, such as EIF5A2, EIF3H, EIF4E, and mTOR. The pro-longevity genes include many cell-cycle progression-related genes involved in DNA damage repair (e.g. XRCC6, ERCC2, and MSH2) or cell-cycle checkpoint regulation genes (e.g. ATM, BRCA1, TP53, TP63, TP73, and BUB1B). LIMITATIONS, REASONS FOR CAUTION Using mature oocytes instead of GV-stage oocytes discarded from ICSI treatments may provide different results. No correction for multiple testing was carried out on individual genes because a small set of longevity-related genes was selected a priori for the analysis. The global trend was corrected for multiple testing and remained significant. This work was an observational study and, as no additional experimental work was performed, the associations described do not directly demonstrate the involvement of such genes in oocyte ageing. WIDER IMPLICATIONS OF THE FINDINGS Growth, metabolism, and cell-cycle progression-related pathways that are known to be involved in somatic cell ageing were associated with ovarian ageing. If experimental data are obtained to support these associations, we suggest that interventions known to modulate these processes could benefit women suffering from ovarian ageing. STUDY FUNDING/COMPETING INTEREST(S) G.E.J. is supported by a VENI grant from ZonMw (https://www.zonmw.nl). Work in the Houtkooper group is financially supported by an ERC Starting grant (No. 638290), a VIDI grant from ZonMw (No. 91715305), and the Velux Stiftung (No. 1063). M.G. declares several research and educational grants from Guerbet, Merck and Ferring (all location VUmc), outside the scope of the submitted work. The other authors report no competing interest TRIAL REGISTRATION NUMBER N/A.

STUDY QUESTION Do parental characteristics and treatment with ART affect perinatal outcomes in singleton pregnancies? SUMMARY ANSWER Both parental and ART treatment characteristics affect perinatal outcomes in singleton pregnancies. WHAT IS KNOWN ALREADY Previous studies have shown that singleton pregnancies resulting from ART are at risk of preterm birth. ART children are lighter at birth after correction for duration of gestation and at increased risk of congenital abnormalities compared to naturally conceived children. This association is confounded by parental characteristics that are also known to affect perinatal outcomes. It is unclear to which extent parental and ART treatment characteristics independently affect perinatal outcomes. STUDY DESIGN, SIZE, DURATION All IVF clinics in the Netherlands (n = 13) were requested to provide data on all ART treatment cycles (IVF, ICSI and frozen-thawed embryo transfers (FET)), performed between 1 January 2000, and 1 January 2011, which resulted in a pregnancy. Using probabilistic data-linkage, these data (n = 36 683) were linked to the Dutch Perinatal Registry (Perined), which includes all children born in the Netherlands in the same time period (n = 2 548 977). PARTICIPANTS/MATERIALS, SETTING, METHODS Analyses were limited to singleton pregnancies that resulted from IVF, ICSI or FET cycles. Multivariable models for linear and logistic regression were fitted including parental characteristics as well as ART treatment characteristics. Analyses were performed separately for fresh cycles and for fresh and FET cycles combined. We assessed the impact on the following perinatal outcomes: birth weight, preterm birth below 37 or 32 weeks of gestation, congenital malformations and perinatal mortality. MAIN RESULTS AND THE ROLE OF CHANCE The perinatal outcomes of 31 184 out of the 36 683 ART treatment cycles leading to a pregnancy were retrieved through linkage with the Perined (85% linkage). Of those, 23 671 concerned singleton pregnancies resulting from IVF, ICSI or FET. Birth weight was independently associated with both parental and ART treatment characteristics. Characteristics associated with lower birth weight included maternal hypertensive disease, non-Dutch maternal ethnicity, nulliparity, increasing duration of subfertility, hCG for luteal phase support (compared to progesterone), shorter embryo culture duration, increasing number of oocytes retrieved and fresh embryo transfer. The parental characteristic with the greatest effect size on birth weight was maternal diabetes (adjusted difference 283 g, 95% CI 228–338). FET was the ART treatment characteristic with the greatest effect size on birth weight (adjusted difference 100 g, 95% CI 84–117) compared to fresh embryo transfer. Preterm birth was more common among mothers of South-Asian ethnicity. Preterm birth was less common among multiparous women and women with ‘male factor’ as treatment indication (compared to ‘tubal factor’). LIMITATIONS, REASONS FOR CAUTION Due to the retrospective nature of our study, we cannot prove causality. Further limitations of our study were the inability to adjust for mothers giving birth more than once in our dataset, missing values for several variables and limited information on parental lifestyle and general health. WIDER IMPLICATIONS OF THE FINDINGS Multiple parental and ART treatment characteristics affect perinatal outcomes, with birth weight being influenced by the widest range of factors. This highlights the importance of assessing both parental and ART treatment characteristics in studies that focus on the health of ART-offspring, with the purpose of modifying these factors where possible. Our results further support the hypothesis that the embryo is sensitive to its early environment. STUDY FUNDING/COMPETING INTEREST(S) This study was funded by Foreest Medical School, Alkmaar, the Netherlands (grants: FIO 1307 and FIO 1505). B.W.M. reports grants from NHMRC and consultancy for ObsEva, Merck KGaA, iGenomics and Guerbet. F.B. reports research support grants from Merck Serono and personal fees from Merck Serono. A.C. reports travel support from Ferring BV. and Theramex BV. and personal fees from UpToDate (Hyperthecosis), all outside the remit of the current work. The remaining authors report no conflict of interests. TRIAL REGISTRATION NUMBER N/A.

IntroductionIn vitro fertilisation (IVF) has evolved as an intervention of choice to help couples with infertility to conceive. In the last decade, a strategy change in the day of embryo transfer has been developed. Many IVF centres choose nowadays to transfer at later stages of embryo development, for example, transferring embryos at blastocyst stage instead of cleavage stage. However, it still is not known which embryo transfer policy in IVF is more efficient in terms of cumulative live birth rate (cLBR), following a fresh and the subsequent frozen–thawed transfers after one oocyte retrieval. Furthermore, studies reporting on obstetric and neonatal outcomes from both transfer policies are limited.Methods and analysisWe have set up a multicentre randomised superiority trial in the Netherlands, named the Three or Fivetrial. We plan to include 1200 women with an indication for IVF with at least four embryos available on day 2 after the oocyte retrieval. Women are randomly allocated to either (1) control group: embryo transfer on day 3 and cryopreservation of supernumerary good-quality embryos on day 3 or 4, or (2) intervention group: embryo transfer on day 5 and cryopreservation of supernumerary good-quality embryos on day 5 or 6. The primary outcome is the cLBR per oocyte retrieval. Secondary outcomes include LBR following fresh transfer, multiple pregnancy rate and time until pregnancy leading a live birth. We will also assess the obstetric and neonatal outcomes, costs and patients’ treatment burden.Ethics and disseminationThe study protocol has been approved by the Central Committee on Research involving Human Subjects in the Netherlands in June 2018 (CCMO NL 64060.000.18). The results of this trial will be submitted for publication in international peer-reviewed and in open access journals.Trial registration numberNetherlands Trial Register (NL 6857).

Background In in vitro fertilisation (IVF) with or without intracytoplasmic sperm injection (ICSI), selection of the most competent embryo(s) for transfer is based on morphological criteria. However, many women do not achieve a pregnancy even after 'good quality' embryo transfer. One of the presumed causes is that such morphologically normal embryos have an abnormal number of chromosomes (aneuploidies). Preimplantation genetic testing for aneuploidies (PGT-A), formerly known as preimplantation genetic screening (PGS), was therefore developed as an alternative method to select embryos for transfer in IVF. In PGT-A, the polar body or one or a few cells of the embryo are obtained by biopsy and tested. Only polar bodies and embryos that show a normal number of chromosomes are transferred. The first generation of PGT-A, using cleavage-stage biopsy and fluorescence in situ hybridisation (FISH) for the genetic analysis, was demonstrated to be ineffective in improving live birth rates. Since then, new PGT-A methodologies have been developed that perform the biopsy procedure at other stages of development and use different methods for genetic analysis. Whether or not PGT-A improves IVF outcomes and is beneficial to patients has remained controversial. Objectives To evaluate the effectiveness and safety of PGT-A in women undergoing an IVF treatment. Search methods We searched the Cochrane Gynaecology and Fertility (CGF) Group Trials Register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, and two trials registers in September 2019 and checked the references of appropriate papers. Selection criteria All randomised controlled trials (RCTs) reporting data on clinical outcomes in participants undergoing IVF with PGT-A versus IVF without PGT-A were eligible for inclusion. Data collection and analysis Two review authors independently selected studies for inclusion, assessed risk of bias, and extracted study data. The primary outcome was the cumulative live birth rate (cLBR). Secondary outcomes were live birth rate (LBR) after the first embryo transfer, miscarriage rate, ongoing pregnancy rate, clinical pregnancy rate, multiple pregnancy rate, proportion of women reaching an embryo transfer, and mean number of embryos per transfer. Main results We included 13 trials involving 2794 women. The quality of the evidence ranged from low to moderate. The main limitations were imprecision, inconsistency, and risk of publication bias. IVF with PGT-A versus IVF without PGT-A with the use of genome-wide analyses Polar body biopsy One trial used polar body biopsy with array comparative genomic hybridisation (aCGH). It is uncertain whether the addition of PGT-A by polar body biopsy increases the cLBR compared to IVF without PGT-A (odds ratio (OR) 1.05, 95% confidence interval (CI) 0.66 to 1.66, 1 RCT, N = 396, low-quality evidence). The evidence suggests that for the observed cLBR of 24% in the control group, the chance of live birth following the results of one IVF cycle with PGT-A is between 17% and 34%. It is uncertain whether the LBR after the first embryo transfer improves with PGT-A by polar body biopsy (OR 1.10, 95% CI 0.68 to 1.79, 1 RCT, N = 396, low-quality evidence). PGT-A with polar body biopsy may reduce miscarriage rate (OR 0.45, 95% CI 0.23 to 0.88, 1 RCT, N = 396, low-quality evidence). No data on ongoing pregnancy rate were available. The effect of PGT-A by polar body biopsy on improving clinical pregnancy rate is uncertain (OR 0.77, 95% CI 0.50 to 1.16, 1 RCT, N = 396, low-quality evidence). Blastocyst stage biopsy One trial used blastocyst stage biopsy with next-generation sequencing. It is uncertain whether IVF with the addition of PGT-A by blastocyst stage biopsy increases cLBR compared to IVF without PGT-A, since no data were available. It is uncertain if LBR after the first embryo transfer improves with PGT-A with blastocyst stage biopsy (OR 0.93, 95% CI 0.69 to 1.27, 1 RCT, N = 661, low-quality evidence). It is uncertain whether PGT-A with blastocyst stage biopsy reduces miscarriage rate (OR 0.89, 95% CI 0.52 to 1.54, 1 RCT, N = 661, low-quality evidence). No data on ongoing pregnancy rate or clinical pregnancy rate were available. IVF with PGT-A versus IVF without PGT-A with the use of FISH for the genetic analysis Eleven trials were included in this comparison. It is uncertain whether IVF with addition of PGT-A increases cLBR (OR 0.59, 95% CI 0.35 to 1.01, 1 RCT, N = 408, low-quality evidence). The evidence suggests that for the observed average cLBR of 29% in the control group, the chance of live birth following the results of one IVF cycle with PGT-A is between 12% and 29%. PGT-A performed with FISH probably reduces live births after the first transfer compared to the control group (OR 0.62, 95% CI 0.43 to 0.91, 10 RCTs, N = 1680, I² = 54%, moderate-quality evidence). The evidence suggests that for the observed average LBR per first transfer of 31% in the control group, the chance of live birth after the first embryo transfer with PGT-A is between 16% and 29%. There is probably little or no difference in miscarriage rate between PGT-A and the control group (OR 1.03, 95%, CI 0.75 to 1.41; 10 RCTs, N = 1680, I² = 16%; moderate-quality evidence). The addition of PGT-A may reduce ongoing pregnancy rate (OR 0.68, 95% CI 0.51 to 0.90, 5 RCTs, N = 1121, I² = 60%, low-quality evidence) and probably reduces clinical pregnancies (OR 0.60, 95% CI 0.45 to 0.81, 5 RCTs, N = 1131; I² = 0%, moderate-quality evidence). Authors' conclusions There is insufficient good-quality evidence of a difference in cumulative live birth rate, live birth rate after the first embryo transfer, or miscarriage rate between IVF with and IVF without PGT-A as currently performed. No data were available on ongoing pregnancy rates. The effect of PGT-A on clinical pregnancy rate is uncertain. Women need to be aware that it is uncertain whether PGT-A with the use of genome-wide analyses is an effective addition to IVF, especially in view of the invasiveness and costs involved in PGT-A. PGT-A using FISH for the genetic analysis is probably harmful. The currently available evidence is insufficient to support PGT-A in routine clinical practice.

Repeated implantation failure (RIF) is a poorly understood reproductive pathology defined by the inability to achieve a clinical pregnancy in at least three consecutive IVF cycles. In this study, we investigated whether the onset of decidualization, marked by prolactin (PRL) expression, is associated with RIF. We performed a retrospective cohort study using endometrial biopsies from women with idiopathic subfertility, that conceived naturally during the same cycle in which the biopsy was taken (group 1; n = 15) conceived naturally within three months after the biopsy was taken (group 2; n = 20), or unsuccessfully underwent six IUI cycles and three IVF cycles with transfer of at least one high-quality embryo (group 3, RIF; n = 20). Our results demonstrated that immunohistochemical PRL-staining was present in 8/15 women from group 1 (53.3%), in 1/20 women from group 2 (5.0%), and in 11/20 women from group 3 (55.0%). Increased proliferation, analyzed by Ki67 expression, was seen in women that were pregnant during the biopsy, compared to all women combined that were not pregnant (p≤.01). In conclusion, our study demonstrates that premature expression of the decidualization marker PRL during the luteal phase is associated with RIF.

[This corrects the article DOI: 10.1093/hropen/hoaa009.][This corrects the article DOI: 10.1093/hropen/hoaa009.].

STUDY QUESTION: What is the difference between the gene expression profiles of single human germinal vesicle (GV) oocytes from women of different ages?SUMMARY ANSWER: There were no statistically significant differences in gene expression profiles of human GV oocytes from women of different ages (range: 25-43).WHAT IS KNOWN ALREADY: It is well established that reproductive capacity declines as women age, which is attributed to oocyte quality since this decline is counterbalanced in older women receiving young donor oocytes. Altered gene expression of human oocytes at different stages of development in relation to female age is one of the suggested mechanisms that could explain the decrease in oocyte quality.STUDY DESIGN, SIZE, DURATION: Between 2012 and 2014, 40 human GV oocytes of 40 women were obtained during follicular aspiration as part of routine ICSI treatment. Gene expression profiles of 38 GV oocytes were determined in four different age groups: 25-30, 31-35, 36-38 and 39-43 years of age.PARTICIPANTS/MATERIALS, SETTING, METHODS: GV oocytes were donated for research and frozen between 3.5 and 7.5 h after follicular aspiration. Subsequently, GV oocytes were thawed and prepared for gene expression profile analysis using Agilent microarrays containing ~42 000 Human Gene Expression probe-sets. Gene expression profiles were visualized by hierarchical clustering and the top 500 most differing genes were determined by multidimensional scaling (MDS). Transcripts were analysed in a class comparison between the four age groups and for indicators of biological age: antral follicle count (AFC) and the total dosage of FSH needed for ovarian stimulation. Individual transcripts were analysed using linear regression. A false discovery rate MAIN RESULTS AND THE ROLE OF CHANCE: Visualization of gene expression profiles of GV oocytes with hierarchal clustering and MDS demonstrated no clear grouping of samples based on female age, AFC or FSH dosage. The gene expression profile of GV oocytes classified in four age groups revealed no significantly differentially expressed genes between the four different age groups. There were also no significantly differentially expressed genes in the linear regression analysis for individual transcripts against age.LARGE SCALE DATA: Not applicable.LIMITATIONS, REASONS FOR CAUTION: Immature (GV) oocytes obtained from ovarian stimulation cycles were used. Findings may therefore differ for oocytes at other developmental stages and for in-vivo matured oocytes under physiological conditions. Due to our relatively large, but still limited study sample (40 GV oocytes), we cannot exclude that there might be smaller age-related gene-expression differences, i.e. due to a lack of power.WIDER IMPLICATIONS OF THE FINDINGS: We did not find an effect of female age on gene expression profiles of individual human GV oocytes. Other studies have suggested that gene-expression profiles are affected in mature oocytes, which might imply that female age affects oocyte maturation. Alternatively, other mechanisms in human oocytes might cause the age-related fertility decline.STUDY FUNDING/COMPETING INTEREST(S): This study received no external funding and there are no competing interests.

STUDY QUESTION: Does Day-3 cleavage-stage PGS affect neurodevelopment of 9-year-old IVF offspring?SUMMARY ANSWER: We did not find evidence of adverse consequences of Day-3 cleavage-stage PGS on neurodevelopment of 9-year-old IVF offspring, although children born after IVF with or without PGS often had a non-optimal neurological condition.WHAT IS KNOWN ALREADY: Knowledge on long-term sequelae for development and health of children born following PGS is lacking. This is striking as evidence accumulates that IVF itself is associated with increased risk for impaired health and development in the offspring.STUDY DESIGN SIZE, DURATION: This prospective, assessor-blinded, multicentre, follow-up study evaluated development and health of 9-year-old IVF children born to women who were randomly assigned to IVF with PGS (PGS group) or without PGS (control group). The follow-up examination at 9 years took place between March 2014 and May 2016.PARTICIPANTS/MATERIALS, SETTING, METHODS: In total, 408 women were included and randomly assigned to IVF with or without Day-3 cleavage-stage PGS. This resulted in 52 ongoing pregnancies in the PGS group and 74 in the control group. In the PGS group, 59 children were born alive; in the control group, 85 children were born alive. At the age of 9 years, 43 children born after PGS and 56 control children participated in the study. Our primary outcome was the neurological optimality score, a sensitive measure of neurological condition assessed with a standardized, age-specific test (Touwen test). Secondary outcomes were adverse neurological condition (neurologically abnormal and the complex form of minor neurological dysfunction), cognitive development (intelligence quotient and specific domains), behaviour (parental and teacher's questionnaires), blood pressure and anthropometrics.MAIN RESULTS AND THE ROLE OF CHANCE: Neurodevelopmental outcome of PGS children did not differ from that of controls; the neurological optimality scores (mean values [(95% CI]: PGS children 51.5 [49.3; 53.7], control children 53.1 [50.5; 55.7]) were not significantly different. The prevalences of adverse neurological outcome (in all but one child implying the presence of the complex form of minor neurological dysfunction) did not differ between the groups (PGS group 17/43 [40%], control group 19/56 [34%]), although the prevalence of complex minor neurological dysfunction in both groups was rather high. Also intelligence quotient scores of the two groups were not significantly different (PGS group 114 [108; 120]); control group 117 [109; 125]), and the behaviour, blood pressure and anthropometrics of both groups did not differ. Mean blood pressures of both groups were above the 60th percentile.LIMITATIONS REASONS FOR CAUTION: The power analysis of the study was not based on the number of children needed for the follow-up study, but on the number of women who were needed to detect an increase in ongoing pregnancy rates after PGS. In addition, our study evaluated embryo biopsy in the form of PGS at cleavage stage (Day-3 embryo biopsy), while currently PGS at blastocyst stage (Day-5 embryo biopsy) is recommended and increasingly being used.WIDER IMPLICATIONS OF THE FINDINGS: Our findings indicate that PGS in cleavage stage embryos is not associated with adverse effects on neurological, cognitive and behavioural development, blood pressure and anthropometrics of offspring at 9 years. This is a reassuring finding as embryo biopsy in the forms of PGS and PGD is increasingly applied. However, both groups of IVF offspring showed high prevalences of the clinically relevant form of minor neurological dysfunction, which is a point of concern for the IVF community. In addition, our study confirms findings of others that IVF offspring may be at risk of an unfavourable cardiovascular outcome. These findings are alarming and highlight the importance of research on the underlying mechanisms of unfavourable neurodevelopmental and cardiovascular outcomes in IVF offspring.STUDY FUNDING/COMPETING INTEREST(S): The randomized controlled trial was financially supported by the Organization for Health Research and Development (ZonMw), The Netherlands (Grant number 945-03-013). The follow-up was financially supported by the University Medical Center Groningen (Grant number: 754510), the Cornelia Foundation, and the graduate schools BCN and Share, Groningen, The Netherlands. The sponsors of the study had no role in study design, data collection, data analysis, data interpretation or writing of the report. There are no conflicts of interest.TRIAL REGISTRATION NUMBER: ISRCTN76355836.

Purpose The purpose of this paper is to study whether human preimplantation embryos regulate endometrial stromal cell (hESC) migration. Methods Primary hESCs were isolated from fertile patients undergoing hysterectomy for benign conditions (uterine scar niche n = 3, dysmenorrhea n = 2; no hormonal treatment). Migration and proliferation assays were performed by culturing decidualized or non-decidualized hESCs in the presence of embryo conditioned medium (ECM) from high-quality embryos (fragmentation ≤ 20%) or from low-quality embryos (fragmentation > 20%) or in non-conditioned medium from the same dishes (control). ECM samples from 425 individually cultured human embryos were used in this study. Results ECM from high-quality embryos, i.e., with a low percentage of fragmentation, actively stimulated decidualized hESC migration (p

Spermatogenesis, starting with spermatogonial differentiation, is characterized by ongoing and dramatic alterations in composition and function of chromatin. Failure to maintain proper chromatin dynamics during spermatogenesis may lead to mutations, chromosomal aberrations or aneuploidies. When transmitted to the offspring, these can cause infertility or congenital malformations. The structural maintenance of chromosomes (SMC) 5/6 protein complex has recently been described to function in chromatin modeling and genomic integrity maintenance during spermatogonial differentiation and meiosis. Among the subunits of the SMC5/6 complex, non-SMC element 2 (NSMCE2) is an important small ubiquitin-related modifier (SUMO) ligase. NSMCE2 has been reported to be essential for mouse development, prevention of cancer and aging in adult mice and topological stress relief in human somatic cells. By using in vitro cultured primary mouse spermatogonial stem cells (SSCs), referred to as male germline stem (GS) cells, we investigated the function of NSMCE2 during spermatogonial proliferation and differentiation. We first optimized a protocol to generate genetically modified GS cell lines using CRISPR-Cas9 and generated an Nsmce2−/− GS cell line. Using this Nsmce2−/− GS cell line, we found that NSMCE2 was dispensable for proliferation, differentiation and topological stress relief in mouse GS cells. Moreover, RNA sequencing analysis demonstrated that the transcriptome was only minimally affected by the absence of NSMCE2. Only differential expression of Sgsm1 appeared highly significant, but with SGSM1 protein levels being unaffected without NSMCE2. Hence, despite the essential roles of NSMCE2 in somatic cells, chromatin integrity maintenance seems differentially regulated in the germline.

Study question Is there a difference in DNA methylation status of imprinted genes in placentas derived from IVF conceptions where embryo culture was performed in human tubal fluid (HTF) versus G5 culture medium? Summary answer We found no statistically significant differences in the mean DNA methylation status of differentially methylated regions (DMRs) associated with parentally imprinted genes in placentas derived from IVF conceptions cultured in HTF versus G5 culture medium. What is known already Animal studies indicate that the embryo culture environment affects the DNA methylation status of the embryo. In humans, birthweight is known to be affected by the type of embryo culture medium used. The effect of embryo culture media on pregnancy, birth and child development may thus be mediated by differential methylation of parentally imprinted genes in the placenta. Study design, size, duration To identify differential DNA methylation of imprinted genes in human placenta derived from IVF conceptions exposed to HTF or G5 embryo culture medium, placenta samples (n = 43 for HTF, n = 54 for G5) were collected between 2010 and 2012 s as part of a multi-center randomized controlled trial in the Netherlands comparing these embryo culture media. Placenta samples from 69 naturally conceived (NC) live births were collected during 2008–2013 in the Netherlands as reference material. Participants/materials, setting, methods To identify differential DNA methylation of imprinted genes, we opted for an amplicon-based sequencing strategy on an Illumina MiSeq sequencing platform. DNA was isolated and 34 DMRs associated with well-defined parentally imprinted genes were amplified in a two-step PCR before sequencing using MiSeq technology. Sequencing data were analyzed in a multivariate fashion to eliminate possible confounding effects. Main results and the role of chance We found no statistically significant differences in the mean DNA methylation status of any of the imprinted DMRs in placentas derived from IVF conceptions cultured in HTF or G5 culture medium. We also did not observe any differences in the mean methylation status per amplicon nor in the variance in methylation per amplicon between the two culture medium groups. A separate surrogate variable analysis also demonstrated that the IVF culture medium was not associated with the DNA methylation status of these DMRs. The mean methylation level and variance per CpG was equal between HTF and G5 placenta. Additional comparison of DNA methylation status of NC placenta samples revealed no statistically significant differences in mean amplicon and CpG methylation between G5, HTF and NC placenta; however, the number of placenta samples exhibiting outlier methylation levels was higher in IVF placenta compared to NC (P Limitations, reasons for caution Due to practical reasons, not all placentas were collected during the trial, and we collected the placentas from natural conceptions from a different cohort, potentially creating bias. We limited ourselves to the DNA methylation status of 34 imprinted DMRs, and we studied only the placenta and no other embryo-derived tissues. Wider implications of the findings It has often been postulated, but has yet to be rigorously tested, that imprinting mediates the effects of embryo culture conditions on pregnancy, birth and child development in humans. Since we did not detect any statistically significant effects of embryo culture conditions on methylation status of imprinted genes in the placenta, this suggests that other unexplored mechanisms may underlie these effects. The biological and clinical relevance of detected outliers with respect to methylation levels of CpGs and DMR require additional analysis in a larger sample size as well. Given the importance and the growing number of children born through IVF, research into these molecular mechanisms is urgently needed. Study funding/competing interest(s) This study was funded by the March of Dimes grant number #6-FY13-153. The authors have no conflicts of interest. Trial registration number Placental biopsies were obtained under Netherlands Trial Registry number 1979 and 1298.

Subfertility is common and affects one in six couples, half of whom lack an explanation for their delay in conceiving. Developments in the diagnosis and treatment of subfertility over the past 50 years have been truly remarkable. Indeed, current generations of couples with subfertility are more fortunate than previous generations, as they have many more opportunities to become parents. The timely access to effective treatment for subfertility is important as many couples have a narrow window of opportunity before the age-related effects of subfertility limit the likelihood of success. Assisted reproduction can overcome the barriers to fertility caused by tubal disease and low sperm count, but little progress has been made in reducing the effect of increasing age on ovarian function. The next 5–10 years will likely see further increases in birth rates in women with subfertility, a greater awareness of lifestyle factors and a possible refinement of current assisted reproduction techniques and the development of new ones. Such progress will bring challenging questions regarding the potential benefits and harms of treatments involving germ cell manipulation, artificial gametes, genetic screening of embryos and gene editing of embryos. We hope to see a major increase in fertility awareness, access to safe and cost-effective fertility care in low-income countries and a reduction in the current disparity of access to fertility care.

Body fluids contain extracellular vesicles expressing tissue factor on their surface and serve as an additional trigger for coagulation. During the menstrual cycle ovarian tissue restoration is mandatory and it is unknown whether follicular fluid might provide procoagulant substances. Within an observational study, follicular fluid from women undergoing IVF/intracytoplasmic sperm injection (ICSI) was analysed by fluorescence-activated cell sorting (FACS), electron microscopy, resistive pulse sensing (RPS), nanoparticle-tracking analysis (NTA) and fibrin generation tests (FGT). The presence of extracellular vesicles, especially CD9-positive extracellular vesicles in follicular fluid, was proven. However, clotting tests revealed no procoagulant properties of the detected extracellular vesicles.

Item does not contain fulltext STUDY QUESTION: Does embryo culture medium influence pregnancy and perinatal outcome in IVF? SUMMARY ANSWER: Embryo culture media used in IVF affect treatment efficacy and the birthweight of newborns. WHAT IS KNOWN ALREADY: A wide variety of culture media for human preimplantation embryos in IVF/ICSI treatments currently exists. It is unknown which medium is best in terms of clinical outcomes. Furthermore, it has been suggested that the culture medium used for the in vitro culture of embryos affects birthweight, but this has never been demonstrated by large randomized trials. STUDY DESIGN, SIZE, DURATION: We conducted a multicenter, double-blind RCT comparing the use of HTF and G5 embryo culture media in IVF. Between July 2010 and May 2012, 836 couples (419 in the HTF group and 417 in the G5 group) were included. The allocated medium (1:1 allocation) was used in all treatment cycles a couple received within 1 year after randomization, including possible transfers with frozen-thawed embryos. The primary outcome was live birth rate. PARTICIPANTS/MATERIALS, SETTING, METHODS: Couples that were scheduled for an IVF or an ICSI treatment at one of the six participating centers in the Netherlands or their affiliated clinics. MAIN RESULTS AND THE ROLE OF CHANCE: The live birth rate was higher, albeit nonsignificantly, in couples assigned to G5 than in couples assigned to HTF (44.1% (184/417) versus 37.9% (159/419); RR: 1.2; 95% confidence interval (CI): 0.99-1.37; P = 0.08). Number of utilizable embryos per cycle (2.8 +/- 2.3 versus 2.3 +/- 1.8; P < 0.001), implantation rate after fresh embryo transfer (20.2 versus 15.3%; P < 0.001) and clinical pregnancy rate (47.7 versus 40.1%; RR: 1.2; 95% CI: 1.02-1.39; P = 0.03) were significantly higher for couples assigned to G5 compared with those assigned to HTF. Of the 383 live born children in this trial, birthweight data from 380 children (300 singletons (G5: 163, HTF: 137) and 80 twin children (G5: 38, HTF: 42)) were retrieved. Birthweight was significantly lower in the G5 group compared with the HTF group, with a mean difference of 158 g (95% CI: 42-275 g; P = 0.008). More singletons were born preterm in the G5 group (8.6% (14/163) versus 2.2% (3/137), but singleton birthweight adjusted for gestational age and gender (z-score) was also lower in the G5 than in the HTF group (-0.13 +/- 0.08 versus 0.17 +/- 0.08; P = 0.008). LIMITATIONS, REASONS FOR CAUTION: This study was powered to detect a 10% difference in live births while a smaller difference could still be clinically relevant. The effect of other culture media on perinatal outcome remains to be determined. WIDER IMPLICATIONS OF THE FINDINGS: Embryo culture media used in IVF affect not only treatment efficacy but also perinatal outcome. This suggests that the millions of human embryos that are cultured in vitro each year are sensitive to their environment. These findings should lead to increased awareness, mechanistic studies and legislative adaptations to protect IVF offspring during the first few days of their existence. STUDY FUNDING/COMPETING INTERESTS: This project was partly funded by The NutsOhra foundation (Grant 1203-061) and March of Dimes (Grant 6-FY13-153). The authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: NTR1979 (Netherlands Trial Registry). TRIAL REGISTRATION DATE: 1 September 2009. DATE OF FIRST PATIENT'S ENROLMENT: 18 July 2010.

STUDY QUESTION: We wanted to probe the opinions and current practices on preimplantation genetic screening (PGS), and more specifically on PGS in its newest form: PGS 2.0? STUDY FINDING: Consensus is lacking on which patient groups, if any at all, can benefit from PGS 2.0 and, a fortiori, whether all IVF patients should be offered PGS. WHAT IS KNOWN ALREADY: It is clear from all experts that PGS 2.0 can be defined as biopsy at the blastocyst stage followed by comprehensive chromosome screening and possibly combined with vitrification. Most agree that mosaicism is less of an issue at the blastocyst stage than at the cleavage stage but whether mosaicism is no issue at all at the blastocyst stage is currently called into question. STUDY DESIGN, SAMPLES/MATERIALS, METHODS: A questionnaire was developed on the three major aspects of PGS 2.0: the Why, with general questions such as PGS 2.0 indications; the How, specifically on genetic analysis methods; the When, on the ideal method and timing of embryo biopsy. Thirty-five colleagues have been selected to address these questions on the basis of their experience with PGS, and demonstrated by peer-reviewed publications, presentations at meetings and participation in the discussion. The first group of experts who were asked about 'The Why' comprised fertility experts, the second group of molecular biologists were asked about 'The How' and the third group of embryologists were asked about 'The When'. Furthermore, the geographical distribution of the experts has been taken into account. Thirty have filled in the questionnaire as well as actively participated in the redaction of the current paper. MAIN RESULTS AND THE ROLE OF CHANCE: The 30 participants were from Europe (Belgium, Germany, Greece, Italy, Netherlands, Spain, UK) and the USA. Array comparative genome hybridization is the most widely used method amongst the participants, but it is slowly being replaced by massive parallel sequencing. Most participants offering PGS 2.0 to their patients prefer blastocyst biopsy. The high efficiency of vitrification of blastocysts has added a layer of complexity to the discussion, and it is not clear whether PGS in combination with vitrification, PGS alone, or vitrification alone, followed by serial thawing and eSET will be the favoured approach. The opinions range from in favour of the introduction of PGS 2.0 for all IVF patients, over the proposal to use PGS as a tool to rank embryos according to their implantation potential, to scepticism towards PGS pending a positive outcome of robust, reliable and large-scale RCTs in distinct patient groups. LIMITATIONS, REASONS FOR CAUTION: Care was taken to obtain a wide spectrum of views from carefully chosen experts. However, not all invited experts agreed to participate, which explains a lack of geographical coverage in some areas, for example China. This paper is a collation of current practices and opinions, and it was outside the scope of this study to bring a scientific, once-and-for-all solution to the ongoing debate. WIDER IMPLICATIONS OF THE FINDINGS: This paper is unique in that it brings together opinions on PGS 2.0 from all different perspectives and gives an overview of currently applied technologies as well as potential future developments. It will be a useful reference for fertility specialists with an expertise outside reproductive genetics. LARGE SCALE DATA: none. STUDY FUNDING AND COMPETING INTERESTS: No specific funding was obtained to conduct this questionnaire.

Lifelong mammalian male fertility is maintained through an intricate balance between spermatogonial proliferation and differentiation. DNA damage in spermatogonia, for instance caused by chemo- or radiotherapy, can induce cell cycle arrest or germ cell apoptosis, possibly resulting in male infertility. Spermatogonia are generally more radiosensitive and prone to undergo apoptosis than somatic cells. Among spermatogonial sub-types the response to DNA damage is differentially modulated; undifferentiated spermatogonia, including the spermatogonial stem cells (SSCs), are relatively radio-resistant, whereas differentiating spermatogonia are very radiosensitive. To investigate the molecular mechanisms underlying this difference, we used an in vitro system consisting of mouse male germline stem (GS) cells that can be induced to differentiate. Using RNA-sequencing analysis, we analyzed the response of undifferentiated and differentiating GS cells to ionizing radiation (IR). At the RNA expression level, both undifferentiated and differentiating GS cells showed a very similar response to IR. Protein localization of several genes found to be involved in either spermatogonial differentiation or radiation response was investigated using mouse testis sections. For instance, we found that the transcription factor PDX1 was specifically expressed in undifferentiated spermatogonia and thus may be a novel marker for these cells. Interestingly, also at the protein level, undifferentiated GS cells showed a more pronounced upregulation of p53 in response to IR than differentiating GS cells. The higher p53 protein level in undifferentiated spermatogonia may preferentially induce cell cycle arrest, thereby giving these cells more time to repair inflicted DNA damage and increase their radio-resistance.

Research question How stable is the pH of human preimplantation embryo culture media during IVF culture and is there variation in pH between batches of culture media? Design To evaluate pH stability, three batches of three culture media were incubated in triplicate without embryos (sham culture) at CO2 levels recommended by the manufacturers (5% or 6%) for 4 days. To evaluate differences in pH between batches, the pH of three batches of five culture media was measured in triplicate during 1 day of sham culture. Linear mixed models were used for the analysis. Results An increase in pH during 4 days of culture was found in all three culture media, but the observed increased values were within the generally accepted range for clinical practice (pH 7.2–7.4). One medium was pH 7.1 in the first 2 days, but this was within the range provided by the manufacturer for that medium. Three out of five analysed media showed batch variation in pH that exceeded the generally accepted range for clinical practice. Conclusions A relevant difference in pH was found between batches of human preimplantation embryo culture media. This suggests that the CO2 level of incubators may need to be adjusted for new batches of culture medium based on measured pH, to anticipate batch variability and safely accommodate limited pH increase over time. This study was unable to identify the cause of the differences in pH between batches, and further investigation on a larger number of batches and other media seems warranted.

STUDY QUESTION Is IVF with frozen-thawed blastocyst transfer (freeze-all strategy) more effective than IVF with fresh and frozen-thawed blastocyst transfer (conventional strategy)? SUMMARY ANSWER The freeze-all strategy was inferior to the conventional strategy in terms of cumulative ongoing pregnancy rate per woman. WHAT IS KNOWN ALREADY IVF without transfer of fresh embryos, thus with frozen-thawed embryo transfer only (freeze-all strategy), is increasingly being used in clinical practice because of a presumed benefit. It is still unknown whether this new IVF strategy increases IVF efficacy. STUDY DESIGN, SIZE, DURATION A single-centre, open label, two arm, parallel group, randomised controlled superiority trial was conducted. The trial was conducted between January 2013 and July 2015 in the Netherlands. The intervention was one IVF cycle with frozen-thawed blastocyst transfer(s) versus one IVF cycle with fresh and frozen-thawed blastocyst transfer(s). The primary outcome was cumulative ongoing pregnancy resulting from one IVF cycle within 12 months after randomisation. Couples were allocated in a 1:1 ratio to the freeze-all strategy or the conventional strategy with an online randomisation programme just before the start of down-regulation. PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were subfertile couples with any indication for IVF undergoing their first IVF cycle, with a female age between 18 and 43 years. Differences in cumulative ongoing pregnancy rates were expressed as relative risks (RR) with 95% CI. All outcomes were analysed following the intention-to-treat principle. MAIN RESULTS AND THE ROLE OF CHANCE Two-hundred-and-five couples were randomly assigned to the freeze-all strategy (n = 102) or to the conventional strategy (n = 102). The cumulative ongoing pregnancy rate per woman was significantly lower in women allocated to the freeze-all strategy (19/102 (19%)) compared to women allocated to the conventional strategy (32/102 (31%); RR 0.59; 95% CI 0.36–0.98). LIMITATIONS, REASONS FOR CAUTION As this was a single-centre study, we were unable to study differences in study protocols and clinic performance. This, and the limited sample size, should make one cautious in using the results as the basis for definitive policy. All patients undergoing IVF, including those with a poor prognosis, were included; therefore, the outcome could differ in women with a good prognosis of IVF treatment success. WIDER IMPLICATIONS OF THE FINDINGS Our results indicate that there might be no benefit of a freeze-all strategy in terms of cumulative ongoing pregnancy rates. The efficacy of the freeze-all strategy in subgroups of patients, different stages of embryo development, and different freezing protocols needs to be further established and balanced against potential benefits and harms for mothers and children. STUDY FUNDING/COMPETING INTEREST(S) The Netherlands Organisation for Health Research and Development (ZonMW grant 171101007). S.M., F.M. and M.v.W. stated they are authors of the Cochrane review ‘Fresh versus frozen embryo transfers in assisted reproduction’. TRIAL REGISTRATION NUMBER Dutch Trial Register, NTR3187 TRIAL REGISTRATION DATE 9 December 2011 DATE OF FIRST PATIENT’S ENROLMENT 8 January 2013

BACKGROUND: In vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) treatments conventionally consist of a fresh embryo transfer, possibly followed by one or more cryopreserved embryo transfers in subsequent cycles. An alternative option is to freeze all suitable embryos and transfer cryopreserved embryos in subsequent cycles only, which is known as the 'freeze all' strategy. This is the first update of the Cochrane Review on this comparison. OBJECTIVES: To evaluate the effectiveness and safety of the freeze all strategy compared to the conventional IVF/ICSI strategy in women undergoing assisted reproductive technology. SEARCH METHODS: We searched the Cochrane Gynaecology and Fertility Group Trials Register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, and two registers of ongoing trials from inception until 23 September 2020 for relevant studies, checked references of publications found, and contacted study authors to obtain additional data. SELECTION CRITERIA: Two review authors (TZ and MZ) independently selected studies for inclusion, assessed risk of bias, and extracted study data. We included randomised controlled trials comparing a 'freeze all' strategy with a conventional IVF/ICSI strategy including a fresh embryo transfer in women undergoing IVF or ICSI treatment. DATA COLLECTION AND ANALYSIS: The primary outcomes were cumulative live birth rate and ovarian hyperstimulation syndrome (OHSS). Secondary outcomes included effectiveness outcomes (including ongoing pregnancy rate and clinical pregnancy rate), time to pregnancy and obstetric, perinatal and neonatal outcomes. MAIN RESULTS: We included 15 studies in the systematic review and eight studies with a total of 4712 women in the meta‐analysis. The overall evidence was of moderate to low quality. We graded all the outcomes and downgraded due to serious risk of bias, serious imprecision and serious unexplained heterogeneity. Risk of bias was associated with unclear blinding of investigators for preliminary outcomes of the study during the interim analysis, unit of analysis error, and absence of adequate study termination rules. There was an absence of high‐quality evidence according to GRADE assessments for our primary outcomes, which is reflected in the cautious language below. There is probably little or no difference in cumulative live birth rate between the 'freeze all' strategy and the conventional IVF/ICSI strategy (odds ratio (OR) 1.08, 95% CI 0.95 to 1.22; I(2) = 0%; 8 RCTs, 4712 women; moderate‐quality evidence). This suggests that for a cumulative live birth rate of 58% following the conventional strategy, the cumulative live birth rate following the 'freeze all' strategy would be between 57% and 63%. Women might develop less OHSS after the 'freeze all' strategy compared to the conventional IVF/ICSI strategy (OR 0.26, 95% CI 0.17 to 0.39; I(2) = 0%; 6 RCTs, 4478 women; low‐quality evidence). These data suggest that for an OHSS rate of 3% following the conventional strategy, the rate following the 'freeze all' strategy would be 1%. There is probably little or no difference between the two strategies in the cumulative ongoing pregnancy rate (OR 0.95, 95% CI 0.75 to 1.19; I(2) = 31%; 4 RCTs, 1245 women; moderate‐quality evidence). We could not analyse time to pregnancy; by design, time to pregnancy is shorter in the conventional strategy than in the 'freeze all' strategy when the cumulative live birth rate is comparable, as embryo transfer is delayed in a 'freeze all' strategy. We are uncertain whether the two strategies differ in cumulative miscarriage rate because the evidence is very low quality (Peto OR 1.06, 95% CI 0.72 to 1.55; I(2) = 55%; 2 RCTs, 986 women; very low‐quality evidence) and cumulative multiple‐pregnancy rate (Peto OR 0.88, 95% CI 0.61 to 1.25; I(2) = 63%; 2 RCTs, 986 women; very low‐quality evidence). The risk of hypertensive disorders of pregnancy (Peto OR 2.15, 95% CI 1.42 to 3.25; I(2) = 29%; 3 RCTs, 3940 women; low‐quality evidence), having a large‐for‐gestational‐age baby (Peto OR 1.96, 95% CI 1.51 to 2.55; I(2) = 0%; 3 RCTs, 3940 women; low‐quality evidence) and a higher birth weight of the children born (mean difference (MD) 127 g, 95% CI 77.1 to 177.8; I(2) = 0%; 5 RCTs, 1607 singletons; moderate‐quality evidence) may be increased following the 'freeze all' strategy. We are uncertain whether the two strategies differ in the risk of having a small‐for‐gestational‐age baby because the evidence is low quality (Peto OR 0.82, 95% CI 0.65 to 1.05; I(2) = 64%; 3 RCTs, 3940 women; low‐quality evidence). AUTHORS' CONCLUSIONS: We found moderate‐quality evidence showing that one strategy is probably not superior to the other in terms of cumulative live birth rate and ongoing pregnancy rate. The risk of OHSS may be decreased in the 'freeze all' strategy. Based on the results of the included studies, we could not analyse time to pregnancy. It is likely to be shorter using a conventional IVF/ICSI strategy with fresh embryo transfer in the case of similar cumulative live birth rate, as embryo transfer is delayed in a 'freeze all' strategy. The risk of maternal hypertensive disorders of pregnancy, of having a large‐for‐gestational‐age baby and a higher birth weight of the children born may be increased following the 'freeze all' strategy. We are uncertain if 'freeze all' strategy reduces the risk of miscarriage, multiple pregnancy rate or having a small‐for‐gestational‐age baby compared to conventional IVF/ICSI.

Spermatogenesis, starting with spermatogonial differentiation, is characterized by ongoing and dramatic alterations in composition and function of chromatin. Failure to maintain proper chromatin dynamics during spermatogenesis may lead to mutations, chromosomal aberrations or aneuploidies. When transmitted to the offspring, these can cause infertility or congenital malformations. The structural maintenance of chromosomes (SMC) 5/6 protein complex has recently been described to function in chromatin modeling and genomic integrity maintenance during spermatogonial differentiation and meiosis. Among the subunits of the SMC5/6 complex, non-SMC element 2 (NSMCE2) is an important small ubiquitin-related modifier (SUMO) ligase. NSMCE2 has been reported to be essential for mouse development, prevention of cancer and aging in adult mice and topological stress relief in human somatic cells. By using

Clinical decisions in reproductive medicine are often made in uncertainty. To reduce uncertainty and to improve clinical decision-making, RCTs are increasingly called upon. A key concept underpinning the ethics of RCTs is equipoise. Here, we aimed to dissect the basic reasoning behind the concept of equipoise and we proposed a line of thinking delineating under which conditions it is ethical to design and execute an RCT. This might prevent a priori negative trials, reduce research waste and aid in the design of meaningful ones. It is these trials that will provide insight on how to safely and effectively assist subfertile couples.

Study Question Does the addition of a low-quality embryo in fresh Day 3 double embryo transfer (DET) affect the ongoing pregnancy rate (OPR) and multiple gestation rate in patients with only one or no high-quality embryos available? Summary Answer In patients with only one- or no high-quality embryo available, the addition of a low-quality embryo in fresh Day 3 DET does not improve the OPR but increases multiple gestation rates in fresh DET. What is Known Already Pregnancy rates after DET are considered to be higher compared to single embryo transfer (SET) when analyzed per first embryo transfer only. However, these conclusions are based on RCTs in which mostly patients with two or more high-quality embryos were included, and can therefore not be applied to patients with only one or no high-quality embryo available. This is particularly relevant since it has been suggested that low-quality embryos could impair the implantation of simultaneously transferred embryos by paracrine signaling. Hence, we investigated in patients with only one or no high-quality embryo available whether the addition of a low-quality embryo in DET affects the OPR, multiple gestation rate and miscarriage rate. Study Design, Size Duration This was a retrospective cohort study of 5050 patients receiving 7252 fresh embryo transfers on Day 3 after fertilization in IVF/ICSI cycles from 2012 to 2015 in two academic hospitals. Participants/Materials, Setting, Methods We included all women that received fresh SET or DET with any combination of high-quality embryos (7, 8 or 9 blastomeres, with equal to or 0.05). Limitations Reasons for Caution Limitations to this study include the retrospective design and possible bias between study groups related to embryo transfer policies between 2012 and 2015. Consequently, we may have underestimated pregnancy chances in all DET groups. Furthermore, the OPR was calculated as a percentage of the number of fresh embryo transfers in each study group, and not the total number of started IVF/ICSI cycles. Therefore, the reported pregnancy outcomes may not truly reflect the pregnancy chances of couples at the start of treatment. A possible confounding effect of maternal age in our study is acknowledged but we could not compare clinical outcomes in different age groups separately owing to small sample sizes. Analysis of pregnancy outcomes in lower prognosis patients (higher maternal age, fewer oocytes retrieved) separately is an avenue for future research. Wider Implications of the Findings The decision to perform DET rather than SET in order to increase the OPR per fresh embryo transfer seems not to be justified for those patients with only one or no high-quality embryo(s) available. However, owing to the limitations of this study, prospective RCTs are needed that specifically investigate pregnancy outcomes in patients with only one or no high-quality embryo(s) available in SET and DET. Study Funding/Competing Interests This study was funded by a grant from the joint Amsterdam Reproduction & Development Institute of the Academic Medical Center and VU University Medical Center (www.amsterdam-reproduction-and-development.org). The authors have no conflicts of interest to declare.

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All agree that in hindsight the rapid adoption of preimplantation genetic screening (PGS) using cleavage stage biopsy and fluorescence in situ hybridization (FISH) in routine clinical practice without proper evaluation of (cost-)effectiveness basically resulted in couples paying more money for a less effective treatment. Now, almost 20 years later, we are on the verge of a new era of PGS. But have things really changed or are we simply going back to the future?

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Objective: To evaluate the effect of preimplantation genetic screening (PGS) on morphologic outcome in children.Design: Follow-up of a randomized controlled trial (RCT).Setting: University hospital.Patient(s): Two-year-old children born to mothers who participated in an RCT on the efficacy of PGS: 50 children born after in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) with PGS (intervention group; PGS+) and 72 children born after IVF/ICSI only (control group; PGS-). Sixty-six age-matched children conceived without any form of assisted reproduction were recruited separately in a local public health service center (reference group).Intervention(s): PGS.Main Outcome Measure(s): Body surface examination and anthropometry. The evaluation of morphologic abnormalities allowed assessment of children's phenotype in detail. Morphologic abnormalities were classified as major abnormalities (abnormal development in organogenesis, deformations, disruptions, or dysplasia) and minor anomalies (deviations in phenogenesis).Result(s): The percentage of children with >= 1 major abnormality was 28% in the PGS+ and 35% in the PGS - group [difference - 7%, 95% CI - 23% to 10%]. The percentage of children with >= 1 minor anomaly was 64% in the PGS+ and 67% in the PGS - group [difference - 3%, 95% CI - 15% to 20%]. In the reference group 30% of the children had >= 1 major abnormality [95% CI 20% to 43%] and 74% had >= 1 minor anomaly [95% CI 62% to 84%].Conclusion(s): No statistically significant differences were found in minor anomalies between children conceived after IVF/ICSI with or without PGS. There is = 10% more major abnormalities in children born after PGS. (Fertil Steril (R) 2013;99:408-13. (C) 2013 by American Society for Reproductive Medicine.)

Background Poor ovarian response is a common clinical problem, affecting up to 26% of IVF cycles. For these women, addition of recombinant luteinizing hormone (rLH) to ovarian hyperstimulation with recombinant FSH has a beneficial effect on ongoing pregnancy rates, but its effect on the yield of top-quality embryos is unknown. Methods We conducted a randomized controlled trial in women expected to respond poorly under ovarian hyperstimulation during their first IVF cycle [all women aged 35-41 and women with FSH > 12 IU/ml and antral follicle count (AFC) ≤ 5]. Women were randomly allocated to rFSH and rLH (2:1 ratio) or rFSH alone (control group) after down-regulation with a GnRH agonist. The primary outcome was the proportion of top-quality embryos per woman on the day of transfer. Secondary outcomes were the number of stimulation days, the number of follicles ≥17 mm, the number of oocytes, the fertilization rate, the number of embryos, the number of women with ≥1 top-quality embryo, the biochemical, clinical and ongoing pregnancy rates and the miscarriage rate. Results There were 116 women allocated to the rLH group and 128 allocated to the control group. The proportion of top-quality embryos per woman was 17% in the rLH group and 11% in the control group [mean difference 0.06; 95% confidence interval (CI) -0.01-0.14]. In the rLH and control groups respectively, 47 (41%) and 41 (32%) women had at least one top-quality embryo on the day of transfer (relative risk: 1.3, 95% CI 0.91-1.77). The ongoing pregnancy rate was 13 versus 12% (relative risk: 1.1; 95% CI 0.57-2.16) for the rLH group compared with the control group. Conclusions This study found no significant difference in embryo quality after the addition of rLH to rFSH for ovarian stimulation in women with poor ovarian reserve. Clinical trials identifier NTR1457.

Mitotic errors are common in human preimplantation embryos. The occurrence of mitotic errors is highest during the first three cleavages after fertilization and as a result about three quarters of human preimplantation embryos show aneuploidies and are chromosomally mosaic at day three of development. The origin of these preimplantation mitotic aneuploidies and the molecular mechanisms involved are being discussed in this review. At later developmental stages the mitotic aneuploidy rate is lower. Mechanisms such as cell arrest, apoptosis, active correction of the aneuploidies and preferential allocation of the aneuploid cells to the extra-embryonic tissues could underlie this lower rate. Understanding the mechanisms that cause mitotic aneuploidies in human preimplantation embryos and the way human preimplantation embryos deal with these aneuploidies might lead to ways to limit the occurrence of aneuploidies, in order to ultimately increase the quality of embryos and with that the likelihood of a successful pregnancy in IVF/ICSI. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure. (C) 2012 Elsevier B.V. All rights reserved

BACKGROUND: Although chromosomal mosaicism in human preimplantation embryos has been described for almost two decades, its exact prevalence is still unknown. The prevalence of mosaicism is important in the context of preimplantation genetic screening in which the chromosomal status of an embryo is determined by the analysis of a single cell from that embryo. METHODS: Here we report a systematic review and meta-analysis of studies on the chromosomal constitution of human preimplantation embryos. In 36 studies, out of 2117 citations that met our search criteria, data were provided extensively enough to allow classification of each analysed embryo with prespecified criteria for its chromosomal makeup. The main outcome of this classification was the prevalence of chromosomal mosaicism in human preimplantation embryos. RESULTS: A total of 815 embryos could be classified. Of these, 177 (22%) were diploid, 599 (73%) were mosaic, of which 480 (59% of the total number of embryos) were diploid-aneuploid mosaic and 119 (14% of the total number of embryos) were aneuploid mosaic, and 39 (5%) contained other numerical chromosomal abnormalities. The distribution of the embryos over these categories was associated with the developmental stage of the embryos, the method used for analysis and the number of chromosomes analysed. CONCLUSIONS: Diploid-aneuploid mosaicism is by far the most common chromosomal constitution in spare human preimplantation embryos after IVF. This undermines the reliable determination of the ploidy status of a cleavage-stage embryo based on the analysis of a single cell. Future research should determine the origin and developmental potential of mosaic embryos.

Background Preimplantation genetic screening (PGS) has increasingly been used in the past decade. Here we present a systematic review and meta-analysis of RCTs on the effect of PGS on the probability of live birth after IVF. Methods PubMed and trial registers were searched for RCTs on PGS. Trials were assessed following predetermined quality criteria. The primary outcome was live birth rate per woman, secondary outcomes were ongoing pregnancy rate, miscarriage rate, multiple pregnancy rate and pregnancy outcome. Results Nine RCTs comparing IVF with and without PGS were included in our meta-analysis. Fluorescence in situ hybridization was used in all trials and cleavage stage biopsy was used in all but one trial. PGS significantly lowered live birth rate after IVF for women of advanced maternal age (risk difference: -0.08; 95% confidence interval: -0. 13 to -0.03). For a live birth rate of 26% after IVF without PGS, the rate would be between 13 and 23% using PGS. Trials where PGS was offered to women with a good prognosis and to women with repeated implantation failure suggested similar outcomes. Conclusions There is no evidence of a beneficial effect of PGS as currently applied on the live birth rate after IVF. On the contrary, for women of advanced maternal age PGS significantly lowers the live birth rate. Technical drawbacks and chromosomal mosaicism underlie this inefficacy of PGS. New approaches in the application of PGS should be evaluated carefully before their introduction into clinical practice.

The objective of this systematic review was to assess live birth rates and miscarriage rates after preimplantation genetic screening or natural conception for unexplained recurrent miscarriage. There were no randomized controlled trials or comparative studies found on this topic. Until data from randomized controlled trials become available, this review summarizes the best available evidence of the efficacy of preimplantation genetic screening vs. natural conception. (Fertil Steril (R) 2011; 95: 2153-7. (C) 2011 by American Society for Reproductive Medicine.)

Objective: Although the primary goal of preimplantation genetic screening (PGS) is to increase pregnancy rates in women undergoing IVF/intracytoplasmic sperm injection treatment, it has been suggested that it may also be used as an alternative to prenatal testing for Down syndrome.Design: Trade-off questionnaires.Setting: Two university centers for reproductive medicine.Patient(s): Two hundred forty-four subfertile women.Intervention(s): Scenarios with different pregnancy chances after PGS and with different risk reductions of a Down syndrome pregnancy were presented.Main Outcome Measure(s): Willingness to have PGS performed in the various scenarios.Result(s): In case PGS would discover all Down syndrome embryos without affecting pregnancy chances, 83% of the women would have PGS performed. If PGS lowered pregnancy chances from one in five to one in seven, 36% of the women preferred to have PGS performed. If PGS reduced the chance of a Down syndrome pregnancy with 80% without affecting pregnancy chances, 75% of the women would have PGS performed, and 31% of them would refrain from prenatal testing afterward.Conclusion(s): Most women favor PGS for Down syndrome screening, even if it is not 100% sensitive. The acceptability depends on the effect PGS has on pregnancy chances, and, to a lower extent on its sensitivity to detect Down syndrome embryos.

Objective To develop a reliable, reproducible, and sensitive method for investigating gene-expression profiles from individual human oocytes. Design Five commercially available protocols were investigated for their efficiency to amplify messenger RNA (mRNA) from 54 single human oocytes. Protocols resulting in sufficient yields were further validated using microarray technology. For the validation, mRNA was isolated from 25 human oocytes. To eliminate biological variation, RNA from 13 human oocytes was pooled together and split into 12 identical samples for further mRNA amplification. From 12 oocytes, mRNA was individually isolated. Setting University medical center and university microarray laboratory. Patient(s) Couples undergoing intracytoplasmic sperm injection treatment were asked to donate their immature oocytes for research, and written informed consent was obtained in all cases. Seventy-nine human oocytes were used in total. Intervention(s) None. Main Outcome Measure(s) Amplification efficiency and microarray profiles. Result(s) Two of the five protocols (WT-Ovation One-Direct and Arcturus RiboAMp HS Plus) resulted in sufficient yields and high success rates and were further validated for their performance in obtaining reliable, reproducible, and sensitive expression profiles from individual human oocytes. Evaluation of these two protocols demonstrated that they both displayed low technical variation and produced highly reproducible profiles ( r ≥ 0.95). One of them identified significantly more transcripts but also had a higher number of false discoveries. Conclusion(s) Two protocols generated ample amounts of mRNA for (quantitative) polymerase chain reaction, microarray, and sequencing techniques. Further validation using a design that discriminates between biological and technical variation showed that both protocols can be used for gene-expression profiling of individual human oocytes.

STUDY QUESTION: Is gene expression in human preimplantation embryos affected by the medium used for embryo culture in vitro during an IVF treatment? SUMMARY ANSWER: Six days of in vitro culture of human preimplantation embryos resulted in medium-dependent differences in expression level of genes involved in apoptosis, protein degradation, metabolism and cell-cycle regulation. WHAT IS KNOWN ALREADY: Several human studies have shown an effect of culture medium on embryo development, pregnancy outcome and birthweight. However, the underlying mechanisms in human embryos are still unknown. In animal models of human development, it has been demonstrated that culture of preimplantation embryos in vitro affects gene expression. In humans, it has been found that culture medium affects gene expression of cryopreserved embryos that, after thawing, were cultured in two different media for 2 more days. STUDY DESIGN, SIZE, DURATION: In a multicenter trial, women were randomly assigned to two culture medium groups [G5 and human tubal fluid (HTF)]. Data on embryonic development were collected for all embryos. In one center, embryos originating from two pronuclei (2PN) zygotes that were not selected for transfer or cryopreservation on Day 2 or 3 because of lower morphological quality, were cultured until Day 6 and used in this study, if couples consented. PARTICIPANTS/MATERIALS, SETTING, METHODS: Ten blastocysts each from the G5 and HTF study groups, matched for fertilization method, maternal age and blastocyst quality, were selected and their mRNA was isolated and amplified. Embryos were examined individually for genome-wide gene expression using Agilent microarrays and PathVisio was used to identify the pathways that showed a culture medium-dependent activity. MAIN RESULTS AND THE ROLE OF CHANCE: Expression of 951 genes differed significantly (P < 0.01) between the G5 and HTF groups. Eighteen pathways, involved in apoptosis, metabolism, protein processing and cell-cycle regulation, showed a significant overrepresentation of differentially expressed genes. The DNA replication, G1 to S cell-cycle control and oxidative phosphorylation pathways were up-regulated in the G5 group compared with the HTF group. This is in agreement with the morphological assessment of the 1527 embryos (originating from 2PN zygotes), which showed that embryos consisted of more cells on Day 2 (3.73 +/- 1.30 versus 3.40 +/- 1.35, P < 0.001) and Day 3 (7.00 +/- 2.41 versus 5.84 +/- 2.36, P < 0.001) in the G5 group when compared with the HTF group. Furthermore, the implantation rate was significantly higher in the G5 group compared with the HTF group (26.7% versus 14.7%, P = 0.002) after transfer on the second or the third day after fertilization. LIMITATIONS, REASONS FOR CAUTION: Despite careful matching of the embryos, it cannot be excluded that the differences observed between the study groups are caused by factors that we did not investigate. Extrapolation of these results to embryos used for transfer demands caution as in the present study embryos that were not selected for either embryo transfer or cryopreservation have been used for the culture experiment until Day 6. WIDER IMPLICATIONS OF THE FINDINGS: This study shows that gene expression in human preimplantation embryos is altered by the culture medium used during IVF treatment and provides insight into the biological pathways that are affected. Whether these changes in gene expression have any long-term effects on children born after IVF remains unknown. However, it is possible that early adaptations of the preimplantation embryo to its environment persist during fetal and post-natal development. STUDY FUNDING/COMPETING INTERESTS: No funding and no competing interests declared. TRIAL REGISTRATION NUMBER: Not applicable.

To optimize success rates of IVF, selection of the most viable embryo(s) for transfer has always been essential, as embryos that are cryopreserved are thought to have a reduced chance of implanting after thawing. Recent developments challenge this concept. Evidence is accumulating that all embryos can now be cryopreserved and transferred in subsequent cycles without impairing pregnancy rates or maybe even with an improvement in pregnancy rates. In such a scenario no selection method will ever lead to improved live birth rates, as, by definition, the live birth rate per stimulated IVF cycle can never be improved when all embryos are serially transferred. In fact, selection could then only lower the live birth rate after IVF. The only parameter that could possibly be improved by embryo selection would be time to pregnancy, if embryos with the highest implantation potential are transferred first.

STUDY QUESTION: What is the relative effect of common environmental and biological factors on transcriptome changes during human preimplantation development? SUMMARY ANSWER: Developmental stage and maternal age had a larger effect on the global gene expression profile of human preimplantation embryos than the culture medium or oxygen concentration used in in vitro culture. WHAT IS KNOWN ALREADY: Studies on mouse and bovine embryos have shown that different conditions in the in vitro culture of embryos can lead to changes in transcriptome profiles. For humans, an effect of developmental stage on the transcriptome profile of embryos has been demonstrated, but studies on the effect of maternal age or culture conditions are lacking. STUDY DESIGN, SIZE, DURATION: Donated, good quality, day 4 cryopreserved human preimplantation embryos (N = 89) were randomized to be cultured in one of two culture media (G5 medium or HTF medium) and one of two oxygen concentrations (5% or 20%), with stratification for maternal age. Next to these variables, developmental stage after culture was taken into account in the analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: Embryos that developed to morula or blastocyst stage during these 2 days whose amplified mRNA passed our quality control criteria for microarray hybridization were individually examined for genome-wide gene expression (N = 37). MAIN RESULTS AND THE ROLE OF CHANCE: Based on the number of differentially expressed genes (DEGs), developmental stage (3519 DEGs) and maternal age (1258 DEGs) had a larger effect on the global gene expression profile of human preimplantation embryos than either tested culture medium (596 DEGs) or oxygen concentration (492 DEGs) used during in vitro culture. Interactions between the factors were found, indicating that culture conditions might have a different effect depending on the developmental stage or the maternal age of the embryos. Affected pathways included metabolism, cell cycle processes and oxidative phosphorylation. LIMITATIONS, REASONS FOR CAUTION: Culture of embryos for only 2 days might have limited the effect on global gene expression by the investigated culture conditions. Earlier stages of development (Day 0 until Day 4) were not analyzed and these embryos might respond differently to the experimental conditions. The freezing and thawing procedures might have had an effect on gene expression. RT-PCR validation was not performed due to scarcity of the material. WIDER IMPLICATIONS OF THE FINDINGS: Our results show that when studying gene expression in single human preimplantation embryos under various experimental conditions, one should take into account the confounding effect of biological variables, such as developmental stage and maternal age. This makes these experiments different from gene expression experiments where these variables can be tightly controlled, for example when using cell lines. STUDY FUNDING/COMPETING INTERESTS: This study received no external funding and there were no competing interests.