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STUDY QUESTION Does preconceptional exposure to oil-based iodinated contrast media during hysterosalpingography (HSG) impact children's neurodevelopment compared with exposure to water-based alternatives? SUMMARY ANSWER Our study found no large-sized effects for neurodevelopment in children with preconceptional exposure to oil-based iodinated contrast media during HSG compared with water-based alternatives. WHAT IS KNOWN ALREADY HSG is widely used as a diagnostic tool in the female fertility work-up. Tubal flushing with oil-based iodinated contrast has been shown to enhance fertility outcomes in couples with unexplained infertility, increasing the chances of pregnancy and live birth compared with water-based alternatives. However, oil-based contrast contains higher doses of iodine and has a longer half-life, and concerns exist that iodinated contrast media can affect women's iodine status and cause temporary (sub)clinical hypothyroidism in mothers and/or foetuses. Considering that thyroid hormones are vital to embryonal and foetal brain development, oil-based contrast media use could increase the risk of impaired neurodevelopment in children conceived shortly after HSG. Here we examine neurodevelopmental outcomes in school-aged children conceived after HSG. STUDY DESIGN, SIZE, DURATION This is a long-term follow-up of the H2Oil trial in which oil-based or water-based contrast was used during HSG (Netherlands; 2012–2014; NTR3270). Of 369 children born <6 months after HSG in the study, we contacted the mothers of 140 children who gave consent to be contacted for follow-up. The follow-up study took place from January to July 2022 (NCT05168228). PARTICIPANTS/MATERIALS, SETTINGS, METHODS The study included 69 children aged 6–9 years who were conceived after HSG with oil-based (n = 42) or water-based contrast (n = 27). The assessments targeted intelligence (Wechsler Intelligence Scale for Children), neurocognitive outcomes (computerized neurocognitive tests), behavioural functioning (parent and teacher questionnaires), and academic performance. Linear regression models, adjusted for age, sex, and parental educational attainment were employed to compare groups. MAIN RESULTS AND THE ROLE OF CHANCE School-aged children born to mothers after oil-based contrast HSG did not significantly differ from children born to mothers after water-based contrast HSG, in regards to intelligence, neurocognitive functioning, behavioural functioning, or academic performance, with the exception of better performance for visuomotor integration functions in children exposed to oil-based contrast preconception. After exploratory correction for multiple comparisons, none of the group differences was statistically significant. LIMITATIONS, REASONS FOR CAUTION The small sample size of this follow-up study limited statistical power. This study provides evidence for the absence of large-sized differences between preconceptional exposure to the two contrast media types but does not rule out more subtle effects on neurodevelopment compared to naturally conceived children without preconceptional exposure to HSG. WIDER IMPLICATIONS OF THE FINDINGS This study contributes to our knowledge about the long-term effects of different types of iodinated contrast media used in fertility work-up, indicating that choosing oil-based over water-based iodinated contrast media is unlikely to have major effect on the long-term neurodevelopmental outcomes of children conceived shortly after HSG. However, further research should focus on the overall safety of iodine exposure during HSG, comparing children conceived after HSG to those conceived naturally as both types of contrast contain high amounts of iodine. STUDY FUNDING/COMPETING INTEREST(S) The original H2Oil randomized controlled trial was an investigator-initiated study that was funded by the two academic hospitals now merged into the Amsterdam University Medical Centre. The current follow-up study (Neuro-H2Oil) is funded through a research grant awarded to the authors by the Amsterdam Reproduction & Development (AR&D) research institute. S.K. is funded by a AMC MD/PhD Scholarship from the Amsterdam UMC. S.K. reports holding voluntary roles in the civil society organizations Universities Allied for Essential Medicines and People's Health Movement. V.M. reports receiving travel and speaker fees as well as research grants from Guerbet, Merck and Ferring. K.D. reports receiving travel and speaker fees as well as research grants from Guerbet. BWM is supported by a NHMRC Investigator grant (GNT1176437) and reports consultancy, travel support and research funding from Merck, consultancy for Organon and Norgine, and holding stock from ObsEva. The other authors report no conflict of interest. TRIAL REGISTRATION NUMBER NCT05168228 [ABSTRACT FROM AUTHOR]

STUDY QUESTION What were the frequency and temporal trends of reporting P -values and effect measures in the abstracts of reproductive medicine studies in 1990–2022, how were reported P -values distributed, and what proportion of articles that present with statistical inference reported statistically significant results, i.e. 'positive' results? SUMMARY ANSWER Around one in six abstracts reported P -values alone without effect measures, while the prevalence of effect measures, whether reported alone or accompanied by P -values, has been increasing, especially in meta-analyses and randomized controlled trials (RCTs); the reported P -values were frequently observed around certain cut-off values, notably at 0.001, 0.01, or 0.05, and among abstracts present with statistical inference (i.e. P -value, CIs, or significant terms), a large majority (77%) reported at least one statistically significant finding. WHAT IS KNOWN ALREADY Publishing or reporting only results that show a 'positive' finding causes bias in evaluating interventions and risk factors and may incur adverse health outcomes for patients.   Despite efforts to minimize publication reporting bias in medical research, it remains unclear whether the magnitude and patterns of the bias have changed over time. STUDY DESIGN, SIZE, DURATION We studied abstracts of reproductive medicine studies from 1990 to 2022. The reproductive medicine studies were published in 23 first-quartile journals under the category of Obstetrics and Gynaecology and Reproductive Biology in Journal Citation Reports and 5 high-impact general medical journals (The Journal of the American Medical Association , The Lancet , The BMJ , The New England Journal of Medicine , and PLoS Medicine). Articles without abstracts, animal studies, and non-research articles, such as case reports or guidelines, were excluded. PARTICIPANTS/MATERIALS, SETTING, METHODS Automated text-mining was used to extract three types of statistical significance reporting, including P -values, CIs, and text description. Meanwhile, abstracts were text-mined for the presence of effect size metrics and Bayes factors. Five hundred abstracts were randomly selected and manually checked for the accuracy of automatic text extraction. The extracted statistical significance information was then analysed for temporal trends and distribution in general as well as in subgroups of study designs and journals. MAIN RESULTS AND THE ROLE OF CHANCE A total of 24 907 eligible reproductive medicine articles were identified from 170 739 screened articles published in 28 journals. The proportion of abstracts not reporting any statistical significance inference halved from 81% (95% CI, 76–84%) in 1990 to 40% (95% CI, 38–44%) in 2021, while reporting P -values alone remained relatively stable, at 15% (95% CI, 12–18%) in 1990 and 19% (95% CI, 16–22%) in 2021. By contrast, the proportion of abstracts reporting effect measures alone increased considerably from 4.1% (95% CI, 2.6–6.3%) in 1990 to 26% (95% CI, 23–29%) in 2021. Similarly, the proportion of abstracts reporting effect measures together with P -values showed substantial growth from 0.8% (95% CI, 0.3–2.2%) to 14% (95% CI, 12–17%) during the same timeframe. Of 30 182 statistical significance inferences, 56% (n = 17 077) conveyed statistical inferences via P -values alone, 30% (n = 8945) via text description alone such as significant or non-significant, 9.3% (n = 2820) via CIs alone, and 4.7% (n = 1340) via both CI and P -values. The reported P -values (n = 18 417), including both a continuum of P -values and dichotomized P -values, were frequently observed around common cut-off values such as 0.001 (20%), 0.05 (16%), and 0.01 (10%). Of the 13 200 reproductive medicine abstracts containing at least one statistical inference, 77% of abstracts made at least one statistically significant statement. Among articles that reported statistical inference, a decline in the proportion of making at least one statistically significant inference was only seen in RCTs, dropping from 71% (95% CI, 48–88%) in 1990 to 59% (95% CI, 42–73%) in 2021, whereas the proportion in the rest of study types remained almost constant over the years. Of abstracts that reported P -value, 87% (95% CI, 86–88%) reported at least one statistically significant P -value; it was 92% (95% CI, 82–97%) in 1990 and reached its peak at 97% (95% CI, 93–99%) in 2001 before declining to 81% (95% CI, 76–85%) in 2021. LIMITATIONS, REASONS FOR CAUTION First, our analysis focused solely on reporting patterns in abstracts but not full-text papers; however, in principle, abstracts should include condensed impartial information and avoid selective reporting. Second, while we attempted to identify all types of statistical significance reporting, our text mining was not flawless. However, the manual assessment showed that inaccuracies were not frequent. WIDER IMPLICATIONS OF THE FINDINGS There is a welcome trend that effect measures are increasingly reported in the abstracts of reproductive medicine studies, specifically in RCTs and meta-analyses. Publication reporting bias remains a major concern. Inflated estimates of interventions and risk factors could harm decisions built upon biased evidence, including clinical recommendations and planning of future research. STUDY FUNDING/COMPETING INTEREST(S) No funding was received for this study. B.W.M. is supported by an NHMRC Investigator grant (GNT1176437); B.W.M. reports research grants and travel support from Merck and consultancy from Merch and ObsEva. W.L. is supported by an NHMRC Investigator Grant (GNT2016729). Q.F. reports receiving a PhD scholarship from Merck. The other author has no conflict of interest to declare. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

IVF is the backbone of infertility treatment, but due to its costs, it is not affordable for everyone. The cost of IVF is further escalated by interventions added to the routine treatment, which are claimed to boost pregnancy rates, so-called add-ons. Consequently, it is critical to offset the increased costs of an intervention against a potentially higher benefit. Here, we propose using a simplified framework considering the cost of a standard IVF procedure to create one live-born baby as a benchmark for the cost-effectiveness of other fertility treatments, add-ons inclusive. This framework is a simplified approach to a formal economic evaluation, enabling a rapid assessment of cost effectiveness in clinical settings. For a 30-year-old woman, assuming a 44.6% cumulative live birth rate and a cost of $12 000 per complete cycle, the cost to create one live-born baby would be ∼$27 000 (i.e. willingness to pay). Under this concept, the decision whether to accept or reject a new treatment depends from an economic perspective on the incremental cost per additional live birth from the new treatment/add-on, with the $27 000 per live-born baby as a reference threshold. This threshold can vary with women's age, and other factors such as the economic perspective and risk of side effects can play a role. If a new add-on or treatment costs >$27 000 per live birth, it might be more rational to invest in a new IVF cycle rather than spending on the add-on. With the increasing number of novel technologies in IVF and the lack of a rapid approach to evaluate their cost-effectiveness, this simplified framework will help with a more objective assessment of the cost-effectiveness of infertility treatments, including add-ons. [ABSTRACT FROM AUTHOR]

STUDY QUESTION What is the effect of small follicles on clinical pregnancy and multiple pregnancy rates in women undergoing IUI with ovarian stimulation (IUI-OS)? SUMMARY ANSWER The presence of ≥2 small follicles with a diameter of 10–12 or 12–14 mm was associated with an increased chance of clinical pregnancy and the presence of any 12–14 mm or larger follicles, but not smaller follicles, was statistically significantly associated with an increased risk for multiple pregnancy. WHAT IS KNOWN ALREADY IUI-OS is widely used as the first-line treatment for unexplained or mild male factor infertility. However, IUI is associated with the risk of multiple pregnancy. While the positive association between the number of follicles ≥14 mm and the chance of pregnancy and the risk of multiple pregnancy is known, the impact of smaller follicles is uncertain. STUDY DESIGN, SIZE, DURATION This was a retrospective cohort study that included women undergoing IUI cycles from January 2007 to May 2021 in one assisted reproduction center. PARTICIPANTS/MATERIALS, SETTING, METHODS We studied the impact of the number and size of follicles on trigger day on clinical pregnancy and multiple pregnancy rates. Generalized estimation equation regression models were used to compute unadjusted and adjusted odds ratios and 95% CI in all women and only women who achieved clinical pregnancy separately. The chance of clinical pregnancy and multiple pregnancy for different numbers of small follicles in cycles with one >18-mm follicle was calculated using marginal effects estimate. MAIN RESULTS AND THE ROLE OF CHANCE This cohort included 12 933 IUI cycles in 7504 women. The overall clinical pregnancy rate was 16.1% (2081/12 933), with a multiple pregnancy rate of 10.5% (218/2081). In the adjusted analysis, the chance of clinical pregnancy increased significantly with the increase in the number of follicles with the diameter of 14–16, 16–18, and 18–20 mm. As for 10–12 mm [adjusted odds ratio (aOR) 1.22, 95% CI 1.02–1.46] and 12–14 mm (aOR 1.29, 95% CI 1.07–1.56) follicles, only groups with ≥2 follicles of those sizes showed significantly increased chance of clinical pregnancy. In cycles that led to pregnancy, follicles with the diameter of 12–14 mm were associated with an increased risk of multiple pregnancy (aOR 1.73, 95% CI 1.19–2.53 for one such follicle; aOR 2.27, 95% CI 1.44–3.56 for ≥2 such follicles), while 10- to 12-mm follicles were not significantly associated with multiple pregnancy (aOR 1.18, 95% CI 0.72–1.95 for ≥2 such follicles). The associations of multiple pregnancy were similar when including all cycles. LIMITATIONS, REASONS FOR CAUTION This was a retrospective observational study from a single center. The records of follicle diameter in our center were of a 2-mm interval which limited our ability to analyze the size of follicle as a continuous variable. Also, the number of cycles with a high number of small follicles was still limited which impeded more detailed analysis on the ≥2 follicles subgroup. Similarly, the value of some parts of the marginal probability estimation for multiple pregnancy versus pregnancy according to size and number of follicles was also limited by the low sample size of certain combinations. WIDER IMPLICATIONS OF THE FINDINGS Follicles larger than 10 mm, especially those ≥12 mm, may need to be clearly recorded during transvaginal ultrasound surveillance and their potential effects on both pregnancy and multiple pregnancy can be discussed with couples undergoing IUI. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the National Natural Science Foundation of China (Grant numbers 82201912, 82371651, and 82071615) and Shanghai Sailing Program (21YF1423200). B.W.M. is supported by an NHMRC Investigator grant (GNT1176437). B.W.M. reports consultancy for ObsEva and Merck and travel support from Merck. B.W.M. has received research funding from Ferring and Merck. The authors declare no other competing interests. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

STUDY QUESTION Does the transfer of single low-grade blastocysts result in acceptable reproductive and perinatal outcomes compared to the transfer of single good-grade blastocysts? SUMMARY ANSWER The transfer of single low-grade blastocysts resulted in a reduced live birth rate of around 30% (14% for very low-grade blastocysts) compared to 44% for single good-grade blastocysts, but does not lead to more adverse perinatal outcomes. WHAT IS KNOWN ALREADY It is known that low-grade blastocysts can result in live births. However, the current studies are limited by relatively small sample sizes and single-centre designs. Furthermore, evidence on perinatal outcomes after transferring low-grade blastocysts is limited. STUDY DESIGN, SIZE, DURATION We conducted a multi-centre, multi-national retrospective cohort study of 10 018 women undergoing 10 964 single blastocyst transfer cycles between 2009 and 2020 from 14 clinics across Australia, China, and New Zealand. PARTICIPANTS/MATERIALS, SETTING, METHODS Blastocysts were graded individually based on assessment of the morphology and development of the inner cell mass (ICM) and trophectoderm (TE), and were grouped into three quality categories: good- (AB, AB, or BA), moderate- (BB), and low-grade (grade C for ICM or TE) blastocysts. CC blastocysts were individually grouped as very low-grade blastocysts. Logistic regression with generalized estimating equation was used to analyse the association between blastocyst quality and live birth as well as other reproductive outcomes. Binomial, multinomial logistic, or linear regression was used to investigate the association between blastocyst quality and perinatal outcomes. Odds ratio (OR), adjusted OR (aOR), adjusted regression coefficient, and their 95% CIs are presented. Statistical significance was set at P  <   0.05. MAIN RESULTS AND THE ROLE OF CHANCE There were 4386 good-grade blastocysts, 3735 moderate-grade blastocysts, and 2843 low-grade blastocysts were included in the analysis, for which the live birth rates were 44.4%, 38.6%, and 30.2%, respectively. Compared to good-grade blastocysts, the live birth rate of low-grade blastocysts was significantly lower (aOR of 0.48 (0.41–0.55)). Very low-grade blastocysts were associated with an even lower live birth rate (aOR 0.30 (0.18–0.52)) and their absolute live birth rate was 13.7%. There were 4132 singleton live births included in the analysis of perinatal outcomes. Compared with good-grade blastocysts, low-grade blastocysts had comparable preterm birth rates (<37 weeks, aOR 1.00 (0.65–1.54)), birthweight Z-scores (adjusted regression coefficient 0.02 (0.09–0.14)), and rates of very low birth weight (<1500 g, aOR 0.84 (0.22–3.25)), low birth weight (1500–2500 g, aOR 0.96 (0.56–1.65)), high birth weight (>4500 g, aOR 0.93 (0.37–2.32)), small for gestational age (aOR 1.63 (0.91–2.93)), and large for gestational age (aOR 1.28 (0.97–1.70)). LIMITATIONS, REASONS FOR CAUTION Due to the nature of the retrospective design, residual confounding could not be excluded. In addition, the number of events for some perinatal outcomes was small. Between-operator and between-laboratory variations in blastocyst assessment were difficult to control. WIDER IMPLICATIONS OF THE FINDINGS Patients undergoing IVF should be informed that low-grade blastocysts result in a lower live birth rate, however they do not increase the risk of adverse perinatal outcomes. Further research should focus on the criteria for embryos that should not be transferred and on the follow-up of long-term outcomes of offspring. STUDY FUNDING/COMPETING INTEREST(S) H.Z. is supported by a Monash Research Scholarship. B.W.J.M. is supported by a NHMRC Investigator grant (GNT1176437). R.W. is supported by an NHMRC Emerging Leadership Investigator grant (2009767). B.W.J.M. reports consultancy, travel support, and research funding from Merck. The other authors do not have competing interests to disclose. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

STUDY QUESTION Does ambient temperature exposure affect outcomes including clinical pregnancy and live birth in women undergoing IVF? SUMMARY ANSWER Both extreme cold and hot ambient temperatures were significantly associated with adverse pregnancy outcomes of IVF cycles. WHAT IS KNOWN ALREADY Heat exposure has been linked to adverse pregnancy outcomes worldwide. However, the effect of ambient temperature on infertile women undergoing IVF treatment is unclear. STUDY DESIGN, SIZE, DURATION A retrospective cohort study was conducted from a database of 3452 infertile women who underwent their first fresh or frozen embryo transfer in the Shanghai First Maternity and Infant Hospital from April 2016 to December 2020. PARTICIPANTS/MATERIALS, SETTING, METHODS Daily mean ambient temperature exposure for each patient was obtained based on their residential address. Temperature-stratified multiple logistic regression analysis was performed to investigate associations between temperature exposure and pregnancy outcomes after controlling for confounders. Vulnerable sub-groups were identified using forest plots. MAIN RESULTS AND THE ROLE OF CHANCE The clinical pregnancy rate and live birth rate were 45.7% and 37.1%, respectively. Regarding clinical pregnancy, a higher temperature during cold weather was significantly associated with a higher pregnancy rate in the period about 11 weeks before ovarian stimulation (adjusted odds ratio (aOR) = 1.102, 95% CI: 1.012–1.201). Regarding live birth, an increased temperature during cold weather was significantly related to a higher live birth rate in the period after confirmation of clinical pregnancy or biochemical pregnancy, with the aORs of 6.299 (95% CI: 3.949–10.047) or 10.486 (95% CI: 5.609–19.620), respectively. However, a higher temperature during hot weather was negatively associated with the live birth rate in the periods after confirmation of clinical pregnancy or biochemical pregnancy, with the aORs at 0.186 (95% CI: 0.121–0.285) or 0.302 (95% CI: 0.224–0.406), respectively. Moreover, the decline in live birth rates during cold and hot weather was accompanied by increased rates of early miscarriage (P  < 0.05). Stratified analyses identified susceptibility characteristics among the participants. LIMITATIONS, REASONS FOR CAUTION Climate monitoring data were used to represent individual temperature exposure levels according to the patient's residential address in the study. We were not able to obtain information of personal outdoor activity and use of indoor air conditioners in this retrospective study, which may affect actual temperature exposure. WIDER IMPLICATIONS OF THE FINDINGS This study highlights that the ambient temperature exposure should be taken into account during IVF treatment and afterwards. There is a need to be alert to extremes in cold and hot ambient temperatures, especially during the period of follicle development and pregnancy. With this knowledge, clinicians can scientifically determine the timing of IVF treatment and reinforce patients' awareness of self-protection to minimize adverse pregnancy outcomes associated with extreme temperatures. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by a grant from the Clinical Research Plan of Shanghai Hospital Development Center [SHDC2020CR4080], a grant from the Science and Technology Commission of Shanghai Municipality [19411960500], and two grants from the National Natural Science Foundation of China [81871213, 81671468]. B.W.M. is supported by a NHMRC Investigator grant (GNT1176437). B.W.M. reports consultancy for ObsEva, and research grants from Merck KGaA, Ferring and Guerbet. The other authors have no conflict of interest to declare. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

Study Question: Does in vitro maturation (IVM) result in non-inferior cumulative live birth rates compared to those after standard in vitro fertilization (IVF) in infertile women with polycystic ovary syndrome (PCOS)?Summary Answer: One cycle of IVM, without any stimulation, was inferior to one cycle of standard IVF in women with PCOS in terms of 6-month cumulative live birth rates, when choosing single vitrified-warmed blastocyst transfer.What Is Known Already: IVM is an emerging alternative treatment for women with PCOS who need assisted reproductive technology. Since a minimal or even zero dose of gonadotropins are required in the IVM procedure, the occurrence of ovarian hyperstimulation syndrome (OHSS) is eliminated. Only one clinical trial comparing the pregnancy outcome between IVM with FSH priming and IVF has been reported. However, it is still unknown whether IVM treatment without any stimulation can offer a similar live birth outcome in women with PCOS as compared to that in women receiving the standard IVF procedure with ovarian stimulation.Study Design, Size, Duration: This single-centre, open-label randomized controlled non-inferiority trial in an academic infertility centre in China was performed between March 2018 and July 2019.Participants/materials, Setting, Methods: Women aged 20-38 years with PCOS and infertility scheduled for their first IVF attempt were eligible. In total, 351 women were randomly allocated to receive one cycle of unstimulated IVM (n = 175) or one cycle of standard IVF with a flexible GnRH antagonist protocol and hCG as ovulatory trigger (n = 176). A freeze-all and single blastocyst transfer strategy was used in both groups. The primary outcome was ongoing pregnancy (leading to live birth) within 6 months after randomization. A non-inferiority margin of 15% was considered.Main Results and the Role Of Chance: The IVM procedure without additional gonadotropin resulted in a lower ongoing pregnancy (leading to live birth) within 6 months after randomization compared to standard IVF treatment (22.3% vs. 50.6%; rate difference -28.3%; 95% confidence interval [CI]: -37.9% to -18.7%). Moderate-severe OHSS did not occur in the IVM group, while in the IVF group, ten women (5.7%) had moderate OHSS and one woman (0.6%) had severe OHSS. There was no statistically significant difference in the occurrence of obstetric and perinatal complications.Limitations, Reasons For Caution: The trial was conducted using an IVM protocol without additional stimulation in a single centre, which may limit its generalizability. In addition, a GnRH agonist trigger rather than hCG for IVF stimulation in women with PCOS would be more consistent with current clinical practice.Wider Implications Of the Findings: Although IVM is considered to be a convenient, inexpensive and safe alternative to IVF for women with PCOS, our results indicated that one cycle of IVM without any stimulation was inferior to one cycle of standard IVF in terms of the cumulative live birth rate. The inferiority of IVM without ovarian stimulation could be mainly due to the limitations in the developmental potential of embryos. Further IVM development should be tested and validated in a freeze-only and blastocyst transfer setting. Further RCTs are needed to evaluate the effectiveness and safety of other IVM protocols or multiple cycles of IVM compared to IVF.Study Funding/competing Interest(s): This study was supported by the National Key Research and Development Program of China (2016YFC1000201 and 2018YFC1002104) and the National Science Foundation of China (81730038). B.W.M. is supported by a NHMRC Investigator grant (GNT1176437). All other authors declare no competing interests.Trial Registration Number: Clinicaltrials.gov NCT03463772.Trial Registration Date: 29 January 2018.Date Of First Patient’s Enrolment: 16 March 2018. [ABSTRACT FROM AUTHOR]