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Chromosome imbalance (aneuploidy) is the major cause of pregnancy loss and congenital disorders in humans. Analyses of small biopsies from human embryos suggest that aneuploidy commonly originates during early divisions, resulting in mosaicism. However, the developmental potential of mosaic embryos remains unclear. We followed the distribution of aneuploid chromosomes across 73 unselected preimplantation embryos and 365 biopsies, sampled from four multifocal trophectoderm (TE) samples and the inner cell mass (ICM). When mosaicism impacted fewer than 50% of cells in one TE biopsy (low-medium mosaicism), only 1% of aneuploidies affected other portions of the embryo. A double-blinded prospective non-selection trial (NCT03673592) showed equivalent live-birth rates and miscarriage rates across 484 euploid, 282 low-grade mosaic, and 131 medium-grade mosaic embryos. No instances of mosaicism or uniparental disomy were detected in the ensuing pregnancies or newborns, and obstetrical and neonatal outcomes were similar between the study groups. Thus, low-medium mosaicism in the trophectoderm mostly arises after TE and ICM differentiation, and such embryos have equivalent developmental potential as fully euploid ones., Competing Interests: Declaration of interests A.C., M.P., L.G., C.P., M.F., M.F., J.C., and C.R. are full-time employees of Igenomix. L.R. is the Scientific Director of GeneraLife IVF. She is editor of reproductive biomedicine online and has been associate editor of human reproduction update. She has been the principal investigator of a study sponsored by Merck KGaA. She has received honoraria and consultation fees from Merck, MSD, Ferring, Ibsa, Cooper Surgical, Cook, Nterilizer, Fujifilm-Irvine Scientific, Medea, and Universal Clinics. She is a partner and shareholder of Global Investment Clinics, Genera Health Care, and Nterilizer and has been affiliated with Flam. D.C. is a full-time employee of GeneraLife IVF, where he is the science and research manager. He received paid lectures from Fujifilm-Irvine Scientific. He received paid consultations from Merck. F.B. reports personal fees from Fujifilm-Irvine Scientific, outside the submitted work. A.V. reports personal fees from Gedeon Richter, personal fees from Merck, and personal fees from MSD, outside the submitted work. E.H. and I.V. are supported by an ERC consolidator grant (724718-ReCAP), the Novo Nordisk Foundation Young Investigator Award (NNF15OC0016662), ReproUnion, and the Danish National Research Foundation (center grant 6110-00344B). The views expressed in this article are those of the authors and not necessarily those of the sponsors. The funders of the study had no role in study design, data collection, data analysis, data interpretation, or writing of this article. The corresponding authors had full access to all the data in the study and had final responsibility for the decision to submit for publication. E.H. is the executive board member and chair of the scientific advisory board of ReproUnion, which is co-funded by Ferring Pharmaceuticals. F.M.U. is the scientific director of GeneraLife IVF. He is the president of the Italian Society of Fertility and Sterility (SIFES). He has been the principal investigator of a study sponsored by Merck and by S&R Farmaceutici. He has received honoraria and consultation fees from Merck, Merck Sharp and Dohnme Corporation, Ferring, Institut Biochimique, Cooper Surgical, Cook, Nterilizer, Fujifilm-Irvine Scientific, Medea, and Universal Clinics. He is partner/shareholder of Global Investment Clinics, Genera Health Care, and Nterilizer, and has been of Flam. C.S. is the head of the scientific advisory board of Igenomix. The other authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

The goal of an IVF cycle is the birth of at least one baby per intention to treat. However, IVF cannot confer competence on an embryo, but only can provide each couple with a safe treatment to meet a predetermined chance of success. This commentary highlights how clinical, financial and patient-centred perspectives should be included in the definition of success in IVF. The primary outcome, which is the cumulative live birth delivery rate per intention to treat, must always be complemented by analyses of risks, costs and time invested, as well as by measures of patient satisfaction. Finally, it is essential, whenever clinical conditions exist, to limit treatment discontinuation after failed attempts. Constant monitoring of the data is pivotal and must be adjusted for patient characteristics and compared with national and international registers. The authors aimed to review all these aspects and highlight the points that are still open for discussion. Is it time for a consensus?, (Copyright © 2021. Published by Elsevier Ltd.)

Study Question: Which is the prevalence of a 47,XXY karyotype in human blastocysts biopsied during preimplantation genetic testing for aneuploidies (PGT-A) cycles?, Summary Answer: The prevalence of a 47,XXY karyotype amongst male blastocysts without autosomal aneuploides is ~1%., What Is Known Already: The prevalence of Klinefelter syndrome is estimated as 0.1-0.2% in male newborns. However, the KS phenotype is extremely variable and there are men with a 47,XXY karyotype and less evident signs, who may go undetected. No risk factor for the 47,XXY karyotype in products of conception has been yet clearly defined, and no data are available regarding the prevalence of this karyotype among human preimplantation embryos., Study Design, Size, Duration: This multicentre cohort study involved 7549 blastocysts obtained during 2826 PGT-A cycles performed between April 2013 and September 2017 at six IVF clinics in Italy., Participants/materials, Setting, Methods: During 2826 PGT-A cycles, 7549 blastocysts underwent trophectoderm biopsy and quantitative-PCR-based comprehensive chromosomal testing to predict the karyotype of the corresponding embryos. The results were also presented according to ranges of maternal and paternal age at oocyte retrieval as well as sperm factor and blastocyst quality. Univariate and multivariate logistic regression analyses were conducted to investigate the correlation of possible confounding factors with the prevalence of 47,XXY karyotype., Main Results, the Role of Chance: Overall, 62 blastocysts were 47,XXY or had an XXY karyotype associated with autosomal aneuploidies. After exclusion of the latter, the prevalence of a 47,XXY karyotype among male blastocysts without autosomal aneuploidies was 0.9% (n = 17/1794). A significant correlation was only found for maternal age and blastocyst quality (OR: 1.20, 95% CI: 1.01-1.42; P = 0.04 and OR: 1.6, 95% CI: 1.13-2.45; P = 0.01)., Limitations, Reasons for Caution: These retrospective data have been produced based on a population of infertile couples undergoing IVF and PGT-A, and the women were mainly of advanced maternal age. Moreover, the qPCR technique is validated only to detect full-chromosome uniform aneuploidies in trophectoderm biopsies., Wider Implications of the Findings: The 0.9% prevalence of the 47,XXY karyotype among male blastocysts, when compared with the 0.1-0.2% prevalence reported in the prenatal and postnatal periods, suggests four possible scenarios that require further investigations: (i) the latter prevalence is underestimated; (ii) 47,XXY blastocysts result in a lower implantation rate than euploid embryos (estimated to be ≈50%); (iii) 47,XXY blastocysts result in a higher early miscarriage rate than euploid embryos (estimated to be ≈10%); or (iv) infertile patients of advanced maternal age and referred to IVF/PGT-A produce a higher rate of 47,XXY blastocysts., Study Funding/competing Interest(s): None., Trial Registration Number: N/A.

Objective: To appraise the fertilization rate as a predictive factor for cumulative live birth rate (CLBR).Design: Multicenter retrospective cohort study.Setting: Ten in vitro fertilization clinics, whose data were collected and processed by the assisted reproductive technology (ART) Italian National Registry.Patient(s): 7,968 couples undergoing 9,394 complete intracytoplasmic sperm injection cycles.Intervention(s): None.Main Outcome Measure(s): The primary outcome measure was the CLBR in association with the fertilization rate intervals (<65%-group 1; 65%-80%-group 2; and >80%-group 3). Further data stratification was performed on the basis of maternal age (<34, 35-38, and 39-42 years) and number of retrieved oocytes (5-7, 8-10, and > 10 oocytes).Result(s): The CLBR was progressively higher in relation to the fertilization rate in groups 1, 2, and 3 (20.1%, 34.7%, and 41.3%, respectively). The number of recovered oocytes, embryo number per cycle, and cumulative pregnancy rate followed the same trend. The decrease in CLBR with increasing maternal age was significantly correlated with the fertilization rate and CLBR in all 3 maternal age groups. Multivariate logistic regression analysis showed fertilization rate as a factor independently associated with CLBR.Conclusion(s): The present data indicated a positive association between the fertilization rate and the CLBR, suggesting the predictive clinical relevance of this parameter and its adoption as a key performance indicator. [ABSTRACT FROM AUTHOR]