Ovarian response and embryo ploidy following oral micronized progesterone-primed ovarian stimulation versus GnRH antagonist protocol. A prospective study with repeated ovarian stimulation cycles.

STUDY QUESTION: Is there any difference in ovarian response and embryo ploidy following progesterone-primed ovarian stimulation (PPOS) using micronized progesterone or GnRH antagonist protocol? SUMMARY ANSWER: Pituitary downregulation with micronized progesterone as PPOS results in higher number of oocytes retrieved and a comparable number of euploid blastocysts to a GnRH antagonist protocol. WHAT IS KNOWN ALREADY: Although the GnRH antagonist is considered by most the gold standard protocol for controlling the LH surge during ovarian stimulation (OS) for IVF/ICSI, PPOS protocols are being increasingly used in freeze-all protocols. Still, despite the promising results of PPOS protocols, an early randomized trial reported potentially lower live births in recipients of oocytes resulting following downregulation with medroxyprogesterone acetate as compared with a GnRH antagonist protocol. The scope of the current prospective study was to investigate whether PPOS with micronized progesterone results in an equivalent yield of euploid blastocysts to a GnRH antagonist protocol. STUDY DESIGN, SIZE, DURATION: In this prospective study, performed between September 2019 to January 2022, 44 women underwent two consecutive OS protocols within a period of 6 months in a GnRH antagonist protocol or in a PPOS protocol with oral micronized progesterone. PARTICIPANTS/MATERIALS, SETTING, METHODS: Overall, 44 women underwent two OS cycles with an identical fixed dose of rFSH (225 or 300 IU) in both cycles. Downregulation in the first cycles was performed with the use of a flexible GnRH antagonist protocol (0.25 mg per day as soon as one follicle of 14 mm) and consecutively, after a washout period of 1 month, control of LH surge was performed with 200 mg of oral micronized progesterone from stimulation Day 1. After the completion of both cycles, all generated blastocysts underwent genetic analysis for aneuploidy screening (preimplantation genetic testing for aneuplody, PGT-A). MAIN RESULTS AND THE ROLE OF CHANCE: Comparisons between protocols did not reveal differences between the duration of OS. The hormonal profile on the day of trigger revealed statistically significant differences between protocols in all the tested hormones except for FSH: with significantly higher serum E2 levels, more elevated LH levels and higher progesterone levels in PPOS cycles as compared with antagonist cycles, respectively. Compared with the GnRH antagonist protocol, the PPOS protocol resulted in a significantly higher number of oocytes (12.7 ± 8.09 versus 10.3 ± 5.84; difference between means [DBM] -2.4 [95% CI -4.1 to -0.73]), metaphase II (9.1 ± 6.12 versus 7.3 ± 4.15; DBM -1.8 [95% CI -3.1 to -0.43]), and 2 pronuclei (7.1 ± 4.99 versus 5.7 ± 3.35; DBM -1.5 [95% CI -2.6.1 to -0.32]), respectively. Nevertheless, no differences were observed regarding the mean number of blastocysts between the PPOS and GnRH antagonist protocols (2.9 ± 2.11 versus 2.8 ± 2.12; DBM -0.07 [95% CI -0.67 to 0.53]) and the mean number of biopsied blastocysts (2.9 ± 2.16 versus 2.9 ± 2.15; DBM -0.07 [95% CI -0.70 to 0.56]), respectively. Concerning the euploidy rates per biopsied embryo, a 29% [95% CI 21.8-38.1%] and a 35% [95% CI 26.6-43.9%] were noticed in the PPOS and antagonist groups, respectively. Finally, no difference was observed for the primary outcome, with a mean number of euploid embryos of 0.86 ± 0.90 versus 1.00 ± 1.12 for the comparison of PPOS versus GnRh antagonist. LIMITATIONS, REASONS FOR CAUTION: The study was powered to detect differences in the mean number of euploid embryos and not in terms of pregnancy outcomes. Additionally, per protocol, there was no randomization, the first cycle was always a GnRH antagonist cycle and the second a PPOS with 1 month of washout period in between. WIDER IMPLICATIONS OF THE FINDINGS: In case of a freeze-all protocol, clinicians may safely consider oral micronized progesterone to control the LH surge and patients could benefit from the advantages of a medication of oral administration, with a potentially higher number of oocytes retrieved at a lower cost, without any compromise in embryo ploidy rates. STUDY FUNDING/COMPETING INTEREST(S): This research was supported by an unrestricted grant from Theramex. N.P.P. has received Research grants from Merck Serono, Organon, Ferring Pharmaceutical, Roche, Theramex, IBSA, Gedeon Richter, and Besins Healthcare; honoraria for lectures from: Merck Serono, Organon, Ferring Pharmaceuticals, Besins International, Roche Diagnostics, IBSA, Theramex, and Gedeon Richter; consulting fees from Merck Serono, Organon, Besins Healthcare, and IBSA. M.d.M.V., F.M., and I.R. declared no conflicts of interest. TRIAL REGISTRATION NUMBER: The study was registered at Clinical Trials Gov. (NCT04108039).

Implicit bias in diagnosing mosaicism amongst preimplantation genetic testing providers: results from a multicenter study of 36 395 blastocysts.

STUDY QUESTION: Does the diagnosis of mosaicism affect ploidy rates across different providers offering preimplantation genetic testing for aneuploidies (PGT-A)? SUMMARY ANSWER: Our analysis of 36 395 blastocyst biopsies across eight genetic testing laboratories revealed that euploidy rates were significantly higher in providers reporting low rates of mosaicism. WHAT IS KNOWN ALREADY: Diagnoses consistent with chromosomal mosaicism have emerged as a third category of possible embryo ploidy outcomes following PGT-A. However, in the era of mosaicism, embryo selection has become increasingly complex. Biological, technical, analytical, and clinical complexities in interpreting such results have led to substantial variability in mosaicism rates across PGT-A providers and clinics. Critically, it remains unknown whether these differences impact the number of euploid embryos available for transfer. Ultimately, this may significantly affect clinical outcomes, with important implications for PGT-A patients. STUDY DESIGN, SIZE, DURATION: In this international, multicenter cohort study, we reviewed 36 395 consecutive PGT-A results, obtained from 10 035 patients across 11 867 treatment cycles, conducted between October 2015 and October 2021. A total of 17 IVF centers, across eight PGT-A providers, five countries and three continents participated in the study. All blastocysts were tested using trophectoderm biopsy and next-generation sequencing. Both autologous and donation cycles were assessed. Cycles using preimplantation genetic testing for structural rearrangements were excluded from the analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: The PGT-A providers were randomly categorized (A to H). Providers B, C, D, E, F, G, and H all reported mosaicism, whereas Provider A reported embryos as either euploid or aneuploid. Ploidy rates were analyzed using multilevel mixed linear regression. Analyses were adjusted for maternal age, paternal age, oocyte source, number of embryos biopsied, day of biopsy, and PGT-A provider, as appropriate. We compared associations between genetic testing providers and PGT-A outcomes, including the number of chromosomally normal (euploid) embryos determined to be suitable for transfer. MAIN RESULTS AND THE ROLE OF CHANCE: The mean maternal age (±SD) across all providers was 36.2 (±5.2). Our findings reveal a strong association between PGT-A provider and the diagnosis of euploidy and mosaicism. Amongst the seven providers that reported mosaicism, the rates varied from 3.1% to 25.0%. After adjusting for confounders, we observed a significant difference in the likelihood of diagnosing mosaicism across providers (P < 0.001), ranging from 6.5% (95% CI: 5.2-7.4%) for Provider B to 35.6% (95% CI: 32.6-38.7%) for Provider E. Notably, adjusted euploidy rates were highest for providers that reported the lowest rates of mosaicism (Provider B: euploidy, 55.7% (95% CI: 54.1-57.4%), mosaicism, 6.5% (95% CI: 5.2-7.4%); Provider H: euploidy, 44.5% (95% CI: 43.6-45.4%), mosaicism, 9.9% (95% CI: 9.2-10.6%)); and Provider D: euploidy, 43.8% (95% CI: 39.2-48.4%), mosaicism, 11.0% (95% CI: 7.5-14.5%)). Moreover, the overall chance of having at least one euploid blastocyst available for transfer was significantly higher when mosaicism was not reported, when we compared Provider A to all other providers (OR = 1.30, 95% CI: 1.13-1.50). Differences in diagnosing and interpreting mosaic results across PGT-A laboratories raise further concerns regarding the accuracy and relevance of mosaicism predictions. While we confirmed equivalent clinical outcomes following the transfer of mosaic and euploid blastocysts, we found that a significant proportion of mosaic embryos are not used for IVF treatment. LIMITATIONS, REASONS FOR CAUTION: Due to the retrospective nature of the study, associations can be ascertained, however, causality cannot be established. Certain parameters such as blastocyst grade were not available in the dataset. Furthermore, certain platform-related and clinic-specific factors may not be readily quantifiable or explicitly captured in our dataset. As such, a full elucidation of all potential confounders accounting for variability may not be possible. WIDER IMPLICATIONS OF THE FINDINGS: Our findings highlight the strong need for standardization and quality assurance in the industry. The decision not to transfer mosaic embryos may ultimately reduce the chance of success of a PGT-A cycle by limiting the pool of available embryos. Until we can be certain that mosaic diagnoses accurately reflect biological variability, reporting mosaicism warrants utmost caution. A prudent approach is imperative, as it may determine the difference between success or failure for some patients. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Torres Quevedo Grant, awarded to M.P. (PTQ2019-010494) by the Spanish State Research Agency, Ministry of Science and Innovation, Spain. M.P., L.B., A.R.L., A.L.R.d.C.L., N.P.P., M.P., D.S., F.A., A.P., B.M., L.D., F.V.M., D.S., M.R., E.P.d.l.B., A.R., and R.V. have no competing interests to declare. B.L., R.M., and J.A.O. are full time employees of IB Biotech, the genetics company of the Instituto Bernabeu group, which performs preimplantation genetic testing. M.G. is a full time employee of Novagen, the genetics company of Cegyr, which performs preimplantation genetic testing. TRIAL REGISTRATION NUMBER: N/A.

EuMAR stakeholder engagement: an analysis of medically assisted reproduction (MAR) data collection practices in EU countries†.

STUDY QUESTION: What are the current national medically assisted reproduction (MAR) data collection systems across EU Member States, and how can these countries contribute to a unique, cycle-by-cycle registry for the European Monitoring of Medically Assisted Reproduction (EuMAR) project? SUMMARY ANSWER: The study identified significant variation in MAR data collection practices across Member States, with differences in data types, collection methods, and reporting requirements; the EuMAR project emerges as an opportunity to enhance data standardization and improve MAR data collection in the EU. WHAT IS KNOWN ALREADY: There is a need for new approaches in MAR data collection that include long-term and cross border follow-up. The EuMAR project intends to establish a unified, cycle-by-cycle registry of data on MAR treatments in EU countries, from which accurate cumulative outcomes can be calculated. STUDY DESIGN, SIZE, DURATION: This cross-sectional study involved a survey and interviews with stakeholders from 26 EU Member States conducted in 2023 over a period of seven months. PARTICIPANTS/MATERIALS, SETTING, METHODS: Representatives from national competent authorities and professional associations involved in MAR data collection in EU countries were invited to complete the survey and interviewed to assess current data flows, information requirements, and their interest in the EuMAR project. MAIN RESULTS AND THE ROLE OF CHANCE: Half of the participating countries reported having a national MAR registry with cycle-by-cycle data (n = 13), while 31% reported having a national registry with aggregated data (n = 8) and 19% reported having no national registry (n = 5). Of the countries with a national cycle-by-cycle registry, eight countries collect identifiable data, five countries collect pseudonymized data, and one country collects fully anonymized data. Informed consent is required in 10 countries. The main advantages that participants expected from a European registry like EuMAR were the possibility of obtaining national statistics in the absence of a national registry and improving the calculation of cumulative outcomes. LIMITATIONS, REASONS FOR CAUTION: The results of the study are based on self-reported data, which may be subject to bias, however, the validity of the collected information was verified with different means, including follow-up calls for clarifications and sharing final transcript reports. The feasibility of the proposed data flow models will be tested in a pilot study. WIDER IMPLICATIONS OF THE FINDINGS: Despite the heterogeneity of data collection practices across EU countries, the results show that stakeholders have high expectations of the benefits that the EuMAR registry can bring, namely the improvement of data consistency, cross-border comparability, and cumulative live birth rates, leading to better information for patients, health care providers and policy makers. STUDY FUNDING/COMPETING INTEREST(S): The EuMAR project was co-founded by ESHRE and the European Commission (101079865-EuMAR-EU4H-2021-PJ2). No competing interests were declared. TRIAL REGISTRATION NUMBER: N/A.

Patients with low prognosis in ART: a Delphi consensus to identify potential clinical implications and measure the impact of POSEIDON criteria.

BACKGROUND: Currently, there is no consensus on the optimal management of women with low prognosis in ART. In this Delphi consensus, a panel of international experts provided real-world clinical perspectives on a series of literature-supported consensus statements regarding the overall relevance of the POSEIDON criteria for women with low prognosis in ART. METHODS: Using a Delphi-consensus framework, twelve experts plus two Scientific Coordinators discussed and amended statements and supporting references proposed by the Scientific Coordinators (Round 1). Statements were distributed via an online survey to an extended panel of 53 experts, of whom 36 who voted anonymously on their level of agreement or disagreement with each statement using a six-point Likert-type scale (1 = Absolutely agree; 2 = More than agree; 3 = Agree; 4 = Disagree; 5 = More than disagree; 6 = Absolutely disagree) (Round 2). Consensus was reached if > 66% of participants agreed or disagreed. RESULTS: The extended panel voted on seventeen statements and subcategorized them according to relevance. All but one statement reached consensus during the first round; the remaining statement reached consensus after rewording. Statements were categorized according to impact, low-prognosis validation, outcomes and patient management. The POSEIDON criteria are timely and clinically sound. The preferred success measure is cumulative live birth and key management strategies include the use of recombinant FSH preparations, supplementation with r-hLH, dose increases and oocyte/embryo accumulation through vitrification. Tools such as the ART Calculator and Follicle-to-Oocyte Index may be considered. Validation data from large, prospective studies in each POSEIDON group are now needed to corroborate existing retrospective data. CONCLUSIONS: This Delphi consensus provides an overview of expert opinion on the clinical implications of the POSEIDON criteria for women with low prognosis to ovarian stimulation.

Blastocysts from partial compaction morulae are not defined by their early mistakes.

RESEARCH QUESTION: Is partial compaction during morula formation associated with an embryo's developmental ability and implantation potential? DESIGN: Retrospective analysis of data from 196 preimplantation genetic testing for aneuploidy (PGT-A) cycles. Embryos starting compaction were grouped according to the inclusion or not of all the blastomeres in the forming morula (full compaction or partial compaction). The possible effect of maternal age and ovarian response on compaction was analysed. Morphokinetic characteristics, blastocyst formation rate, morphology and cytogenetic constitution of the obtained blastocysts were compared. Comparisons of reproductive outcomes after the transfer of euploid blastocysts from both groups were established. Finally, in a subset of embryos, the chromosomal constitution concordance of the abandoned cells and the corresponding blastocyst through trophectoderm biopsies was assessed. RESULTS: A total of 430 embryos failed to include at least one cell during compaction (partial compaction group [49.3%]), whereas the 442 remaining embryos formed a fully compacted morula (full compaction group [50.7%]). Neither female age nor the number of oocytes collected affected the prevalence of partial compaction morulae. Morphokinetic parameters were altered in embryos from partial compaction morulae compared with full compaction. Although an impairment in blastocyst formation rate was observed in partial compaction morulae (57.2% versus 70.8%, P < 0.001), both chromosomal constitution (euploidy rate: partial compaction [38.4%] versus full compaction [34.2%]) and reproductive outcomes (live birth rate: partial compaction [51.9%] versus full compaction [46.2%]) of the obtained blastocysts were equivalent between groups. A high ploidy correlation of excluded cells-trophectoderm duos was observed. CONCLUSIONS: Partial compaction morulae show a reduced developmental ability compared with full compaction morulae. Resulting blastocysts from both groups, however, have similar euploidy rates and reproductive outcomes. Cell exclusion might be a consequence of a compromised embryo development regardless of the chromosomal constitution of the excluded cells.

Developing and validating a prediction model of live birth following single vitrified-warmed blastocyst transfer.

RESEARCH QUESTION: Can the developed clinical prediction model offer an accurate estimate of the likelihood of live birth, involving blastocyst morphology and vitrification day after single vitrified-warmed blastocyst transfer (SVBT), and therefore assist clinicians and patients? STUDY DESIGN: Retrospective cohort study conducted at a Spanish university-based reproductive medicine unit (2017-2021) including consecutive vitrified-warmed blastocysts from IVF cycles. A multivariable logistic regression incorporated key live birth predictors: vitrification day, embryo score, embryo ploidy status and clinically relevant variables, i.e. maternal age. RESULTS: The training set involved 1653 SVBT cycles carried out between 2017 and 2020; 592 SVBT cycles from 2021 constituted the external validation dataset. The model revealed that female age and embryo characteristics, including overall quality and blastulation day, is linked to live birth rate in SVBT cycles. Stratification by vitrification day and quality (from day-5A to day-6 C blastocysts) applied to genetically tested and untested embryos. The model's area under the curve was 0.66 (95% CI 0.64 to 0.69) during development and 0.65 (95% CI 0.61 to 0.70) in validation, denoting moderate discrimination. Calibration plots showed strong agreement between predicted and observed probabilities. CONCLUSION: By incorporating essential predictors such as vitrification day, embryo morphology grade, age and preimplantation genetic testing for aneuploidy usage, this predictive model offers valuable guidance to clinicians and patients, enabling accurate forecasts of live birth rates for any given vitrified blastocyst within SVBT cycles. Additionally, it serves as a potentially indispensable laboratory tool, aiding in selecting the most promising blastocysts for optimal outcomes.

Free your patients and yourself from day 2-3: start ovarian stimulation any time in freeze-all cycles.

Ovarian stimulation for assisted reproductive technology is traditionally started in the early follicular phase. The essential rationale is to allow timely follicle growth and oocyte retrieval to ensure synchronization of the in-vitro cultured embryos with the receptive period of the endometrium in a fresh transfer cycle. In addition, conventional thought suggested that follicle recruitment happened only once, around menstruation. A deeper understanding of folliculogenesis, advances in cryobiology and an increasing proportion of freeze-all cycles provide a unique opportunity here. Experience from oncofertility patients as well as infertile women and oocyte donors who underwent ovarian stimulation in different phases of the menstrual cycle, dubbed 'random start' cycles, suggests that the number of oocytes collected and their reproductive potential do not depend on the time of starting ovarian stimulation, although the duration of stimulation and gonadotrophin consumption can vary slightly. It may be time to free both patients and clinics from the obsession with starting ovarian stimulation in the early follicular phase in planned freeze-all cycles. The flexibility provided by random start cycles is one aspect of individualizing treatment to patients' needs.

Association between sequence variants in the FSHR gene and reproductive outcomes following IVF in predicted normoresponders.

RESEARCH QUESTION: Is there an association between FSHR sequence variants and reproductive outcomes following IVF in predicted normoresponders? DESIGN: Multicentre prospective cohort study conducted from November 2016 to June 2019 in Vietnam, Belgium and Spain including patients aged <38 years, and undergoing IVF with a predicted normal response with fixed-dose 150 IU rFSH in an antagonist protocol. Genotyping was performed for three FSHR (c.919A>G, c.2039A>G, c.-29G>A) and one FSHB sequence variants (c.-211G>T). Clinical pregnancy rate (CPR), live birth rate (LBR) and miscarriage rate in the first embryo transfer and cumulative live birth rate (CLBR) were compared between the different genotypes. RESULTS: A total of 351 patients underwent at least one embryo transfer. Genetic model analysis that adjusted for patient age, body mass index, ethnicity, type of embryo transfer, embryo stage and number of top-quality embryos transferred revealed a higher CPR for homozygous patients for the variant allele G of c.919A>G when compared to patients with genotype AA (60.3% versus 46.3%, adjusted odds ratio [ORadj] 1.96, 95% confidence interval [CI] 1.09-3.53). Also, c.919A>G genotypes AG and GG presented a higher CPR and LBR when compared with genotype AA (59.1% versus 46.3%, ORadj 1.80, 95% CI 1.08-3.00, and 51.3% versus 39.0%, ORadj 1.69, 95% CI 1.01-2.80, respectively). Cox regression models revealed a statistically significantly lower CLBR for c.2039A>G genotype GG in the codominant model (hazard ratio [HR] 0.66, 95% CI 0.43-0.99). CONCLUSION: These results demonstrate a previously unreported association between variant c.919A>G genotype GG and higher CPR and LBR in infertile patients and reinforce a potential role for genetic background in predicting the reproductive prognosis following IVF.

Comparison of blastocyst euploidy rates following luteal versus follicular phase stimulation in a GnRH antagonist protocol: a prospective study with repeated ovarian stimulation cycles.

STUDY QUESTION: Is there any difference in the mean number of euploid embryos following luteal phase start (LS) and follicular phase start (FS) of ovarian stimulation? SUMMARY ANSWER: The mean number of euploid blastocysts is equivalent independent of whether the inseminated oocytes are derived from FS or LS. WHAT IS KNOWN ALREADY: Starting ovarian stimulation at any time of the cycle ('random-start') is commonly used for emergency fertility preservation in cancer patients. A few retrospective studies have been published evaluating LS in women undergoing ovarian stimulation in the context of IVF, but there is a lack of robust data on the comparative efficacy of LS versus FS.Although 'random start' is commonly used in cancer survivors, few retrospective and uncontrolled studies have been published evaluating luteal phase stimulation in women undergoing ovarian stimulation in the context of IVF. Owing to this evident lack of robust data on the efficacy of LS, guidelines typically recommend the LS approach only for medical reasons and not in the context of IVF. STUDY DESIGN, SIZE, DURATION: This is a prospective, equivalence study, with repeated stimulation cycles, conducted between May 2018 and December 2021. Overall, 44 oocyte donors underwent two identical consecutive ovarian stimulation cycles, one initiated in the FS and the other in the LS. The primary outcome of the study was to evaluate whether FS and LS in the same patient would result in equivalent numbers of euploid embryos following fertilization of oocytes with the same sperm sample. PARTICIPANTS/MATERIALS, SETTING, METHODS: Overall, 44 oocyte donors underwent two consecutive ovarian stimulation protocols with 150 µg corifollitropin alpha followed by 200 IU recombinant FSH (rFSH) in a fixed GnRH antagonist protocol. The only difference between the two cycles was the day of initiation of ovarian stimulation, which was in the early follicular phase (FS) in one cycle, and in the luteal phase (LS) in the other. Forty-four oocyte recipients participated in the study receiving a mean of six metaphase II (MII) oocytes from each stimulation cycle (FS and LS). All MIIs were inseminated with the corresponding recipient's partner sperm (which had been previously frozen) or donor sperm, in order to safeguard the use of the same sample for either the FS or LS. Following fertilization and blastocyst culture, all generated embryos underwent genetic analysis for aneuploidy screening (preimplantation genetic testing for aneuploidy). MAIN RESULTS AND THE ROLE OF CHANCE: FS resulted in a significantly shorter duration of ovarian stimulation (difference between means (DBM) -1.05 (95% CI -1.89; -0.20)) and a lower total additional dose of daily rFSH was needed (DBM -196.02 (95% CI -319.92; -72.12)) compared with LS. The donors' hormonal profile on the day of trigger was comparable between the two stimulation cycles, as well as the mean number of oocytes (23.70 ± 10.79 versus 23.70 ± 8.81) (DBM 0.00 (95% CI -3.03; 3.03)) and MII oocytes (20.27 ± 9.60 versus 20.73 ± 8.65) (DBM -0.45 (95% CI -2.82; 1.91)) between FS and LS cycles, respectively. Following fertilization, the overall blastocyst formation rate was 60.70% with a euploid rate of 57.1%. Comparisons between the two stimulation cycles did not reveal any significance differences in terms of fertilization rates (71.9% versus 71.4%), blastocyst formation rates (59.4% versus 62%) and embryo euploidy rates (56.9 versus 57.3%) for the comparison of FS versus LS, respectively. The mean number of euploid blastocysts was equivalent between the FS (1.59 ± 1.30) and the LS (1.61 ± 1.17), (DBM -0.02 (90%CI -0.48; 0.44)). LIMITATIONS, REASONS FOR CAUTION: The study was performed in young, potentially fertile oocyte donors who are patients with high blastocyst euploidy rates. Although results may be extrapolated to young infertile women with good ovarian reserve, caution is needed prior to generalizing the results to infertile women of older age. WIDER IMPLICATIONS OF THE FINDINGS: The current study provides evidence that initiation of ovarian stimulation in the luteal phase in young potentially fertile women may result in a comparable number of oocytes and comparable blastocyst euploidy rates compared with follicular phase stimulation. This may imply that in case of a freeze-all protocol in young patients with good ovarian reserve, clinicians may safely consider initiation of ovarian stimulation during the luteal phase. STUDY FUNDING/COMPETING INTEREST(S): This research was supported by an unrestricted grant from MSD/Organon. N.P.P. has received Research grants and honoraria for lectures from: Merck Serono, MSD/Organon, Ferring Pharmaceuticals, Besins Intenational, Roche Diagnostics, IBSA, Theramex, Gedeon Richter. F.M., E.C., M.R. and S.G. declared no conflict of interests. TRIAL REGISTRATION NUMBER: The study was registered at Clinical Trials Gov (NCT03555942).

Recipient outcomes in an oocyte donation programme: should very young donors be excluded?

RESEARCH QUESTION: Does the oocyte donor's age affect live birth rate (LBR) in recipients? DESIGN: Retrospective study of 3766 oocyte recipient cycles carried out between January 2009 and December 2018. Cycles were categorized into groups according to donor's age: <20 years (4.7%); 20-25 years (41.1%); ≥26 years (54.2%). Chi-squared test was used to evaluate differences in LBR and analysis of variance was used to test differences in embryo quality, and fertilization and embryo development rates. A generalized linear mixed model was applied to estimate the odds for each end point. RESULTS: LBR was 40.7%. When analysed according to donors' age, significant differences were found: 33.9% for the youngest group, 39.1% for the group aged 20-25 years, and 42.5% for donors aged ≥26 years (P = 0.022). When adjusting for confounding factors (recipient age, number of transferred embryos and day of embryo transfer), LBR was lower in the group aged <20 years (OR 0.70; CI 95% 0.50 to 0.99) and in the group aged 20-25 years (OR 0.85; CI 95% 0.74 to 0.98) compared with the group aged ≥26 years. No significant differences were observed in fertilization rates (74.2%, 76.1% and 77.5%) or embryo development rates (57.0%, 61.4% and 62.0%). The number of good-quality embryos transferred was significantly lower in the group aged <20 years (1.03 ± 0.71; 1.18 ± 0.69; 1.19 ± 0.67; P = 0.015). CONCLUSIONS: LBR is significantly lower when donors are younger than 25 years and, especially, when they are younger than 20 years.

Blastocyst versus cleavage embryo transfer improves cumulative live birth rates, time and cost in oocyte recipients: a randomized controlled trial.

RESEARCH QUESTION: Does embryo transfer day (day 5 versus day 3) affect cumulative live birth rates (CLBR), time to live birth (TLB) and cost per live birth (CPL) in recipients of donated oocytes? STUDY DESIGN: A single-centre RCT conducted between April 2017 and August 2018. Recipients of donated oocytes were randomized to cleavage-stage (day 3) or to blastocyst-stage (day 5) embryo transfer. Eligible recipients were aged 18-50 years and in their first or second synchronous cycle. Primary outcome was CLBR (12 months from first embryo transfer), and fresh and subsequent cryopreserved transfers were considered; TLB and CPL were also analysed. RESULTS: Recipients (n = 134) were randomized to the day-3 group (n = 69) or to the day-5 group (n = 65). Day-5 transfer resulted in a 15.9% relative increase in CLBR and a significant shorter TLB compared with day-3 transfer. To reach a 50% CLBR, the day-3 group required 6 months more than the day-5 group (15.3 versus 8.9 months, respectively). The average CPL in the day-3 strategy cost 24% more than the day-5 strategy (€14817.10 versus €10959.20). Clinical pregnancy rate was 25% less in the day-3 group. The trial was prematurely stopped after poor initial results in the day-3 arm led to unplanned interim analysis. CONCLUSIONS: The transfer of blastocyst-stage embryos in recipients of donated oocytes is preferred as it leads to a higher clinical pregnancy rate, live birth rate, shorter time to pregnancy and lower costs to achieve live birth, compared with cleavage-stage embryo transfer.

Male and female blastocysts: any difference other than the sex?

RESEARCH QUESTION: Is there any imbalance in the sex ratio at the blastocyst stage of human embryos? And what is the sex ratio in euploid, transferred, implanted blastocysts and at birth? DESIGN: Embryos from 646 women undergoing 921 preimplantation genetic testing for aneuploidy (PGT-A) cycles from September 2017 to February 2020 were included. Data from the chromosomal constitution of 2637 biopsied blastocysts were retrospectively analysed. Trophectoderm samples were analysed by next-generation sequencing. Embryos were categorized as euploid, mosaic or aneuploid. A total of 548 blastocysts diagnosed as euploid were warmed and transferred in a subsequent single-embryo transfer cycle. RESULTS: The blastocyst sex ratio was skewed in favour of male sex with 53.1% (1401/2637) of blastocysts diagnosed as male and 46.9% (1236/2637) as female (sex ratio 1.13, 95% confidence interval [CI] 1.05-1.22). Following biopsy and PGT-A, 41.2% (1086/2637) of blastocysts were classified as euploid, 7.7% (202/2637) as mosaic and 51.2% (1349/2637) as aneuploid. More chromosome euploidy was observed among female than male blastocysts (adjusted odds ratio 1.29, 95% CI 1.08-1.55) after adjusting for female age, male age and gonadotrophin dose. Euploid blastocysts were comparable between the sexes (sex ratio 0.99, 95% CI 0.88-1.11). No significant differences were observed between the sexes in implantation (sex ratio 0.86, 95% CI 0.68-1.08), miscarriage (sex ratio 1, 95% CI 0.51-1.97) or live birth rate (sex ratio 0.85, 95% CI 0.66-1.08). CONCLUSIONS: More male than female embryos develop to the blastocyst stage. Male blastocysts exhibit a higher aneuploidy rate. The capacity to implant and lead to a live birth is similar between the sexes.

Progesterone-primed ovarian stimulation in oocyte donation: a model for elective fertility preservation?

RESEARCH QUESTION: Does type of LH peak suppression (progesterone-primed ovarian stimulation [PPOS] versus gonadotrophin releasing hormone [GnRH] antagonist) affect oocyte competence, embryo development and live birth rates in recipients of vitrified donated oocytes? DESIGN: Retrospective cohort study conducted between 2016 and 2018, involving 187 recipient cycles of donated vitrified oocytes. Oocyte donors were stimulated under LH suppression with desogestrel for PPOS (DSG group) or ganirelix GnRH antagonist (ANT group). Recipients younger than 50 years received vitrified oocytes from DSG donation cycles (DSG-R) or ANT donation cycles (ANT-R). RESULTS: A mean of 10.07 ± 3.54 oocytes per recipient were warmed (survival rate of 80.7%), and 5.90 ± 2.89 were fertilized (fertilization rate 72.6%). Out of 187 recipients, 168 achieved embryo transfers. No significant differences were found in warming survival rates, fertilization rates and embryo development between DSG-R and ANT-R groups. Ninety-four clinical pregnancies and 81 live births were achieved. No statistically significant differences were found in clinical pregnancy rates (47.7% versus 52.5, P = 0.513) and live birth rates (39.5% versus 46.5%, P = 0.336) per recipient cycle between DSG-R and ANT-R, respectively. Multivariable logistic regression was applied to assess the effect of treating oocyte donors. Live birth rate adjusted for associated factors was not statistically different between vitrified oocytes from DSG or ANT (OR 0.74, 95% CI 0.37 to 1.47). CONCLUSION: Reproductive outcomes of recipients of vitrified oocytes are not affected by donor PPOS treatment. PPOS is suitable for suppressing LH peak in elective fertility preservation and in freeze-all strategies.

Androgens and diminished ovarian reserve: the long road from basic science to clinical implementation. A comprehensive and systematic review with meta-analysis.

OBJECTIVE: This study aimed to present a narrative review regarding androgen production, androgens' role in folliculogenesis, and the available therapeutic approaches for androgen supplementation, and to perform a systematic review and meta-analysis regarding the impact of androgens (dehydroepiandrosterone/testosterone) compared with placebo or no treatment on ovarian response and pregnancy outcomes in patients with diminished ovarian reserve and/or poor ovarian responders. DATA SOURCES: An electronic search of MEDLINE, Embase, Cochrane Library, Cochrane Central Register of Controlled Trials, Scopus, ClinicalTrials.gov, the ISRCTN registry, and the World Health Organization International Clinical Trials Registry, was conducted for studies published until September 2021. STUDY ELIGIBILITY CRITERIA: Randomized controlled trials that compared ovarian response and/or pregnancy outcomes between the different in vitro fertilization protocols using androgens (ie, dehydroepiandrosterone and testosterone) and conventional in vitro fertilization stimulation in patients with diminished ovarian reserve and/or poor ovarian responders were included. METHODS: The quality of each study was evaluated with the revised Cochrane risk-of-bias tool for randomized trials (RoB 2). The meta-analysis used random-effects models. All results were interpreted on the basis of intention-to-treat analysis (defined as the inclusion of all randomized patients in the denominator). Risk ratios and 95% confidence intervals were used and combined for meta-analysis. RESULTS: No significant differences were found regarding the number of oocytes retrieved (mean difference, 0.76; 95% confidence interval, -0.35 to 1.88), mature oocytes retrieved (mean difference, 0.25; 95% confidence interval, -0.27 to 0.76), clinical pregnancy rate (risk ratio, 1.17; 95% confidence interval, 0.87-1.57), live-birth rate (risk ratio, 0.97; 95% confidence interval, 0.47-2.01), or miscarriage rate (risk ratio, 0.80; 95% confidence interval, 0.29-2.22) when dehydroepiandrosterone priming was compared with placebo or no treatment. Testosterone pretreatment yielded a higher number of oocytes retrieved (mean difference, 0.94; 95% confidence interval, 0.46-1.42), a higher clinical pregnancy rate (risk ratio, 2.07; 95% confidence interval, 1.33-3.20), and higher live-birth rate (risk ratio, 2.09; 95% confidence interval, 1.11-3.95). CONCLUSION: Although dehydroepiandrosterone did not present a clear effect on outcomes of assisted reproductive techniques, we found a potentially beneficial effect of testosterone priming on ovarian response and pregnancy outcomes. However, results should be interpreted with caution, taking into account the low to moderate quality of the available evidence.

Do reproductive history and information given through genetic counselling influence patients' decisions on mosaic embryo transfer?

OBJECTIVE: To assess patients' and embryonic characteristics that may have an influence on the decision to transfer a mosaic embryo. METHOD: Single centre retrospective cohort study including 1247 PGT-A cycles. Demographic and clinical factors associated with a decision to transfer a mosaic embryo were studied. Female age, number of previous cycles, previous availability of euploid embryos, history of miscarriages and parity as well as percentage of mosaicism, type of anomaly and chromosome risk were studied in relation to decision-making. Outcomes after mosaic embryo transfer were assessed. RESULTS: To date, in 7.9% of cycles (99/1247), patients have had to make a decision on the fate of their mosaic embryos. In 23.2% of cycles (23/99), patients decided to transfer. In most cases (79.8%; 79/99), patients underwent genetic counselling before the decision. None of the variables analysed were associated with the patients' decision, although parity and the high-degree mosaicism (>50%) seemed to be negatively associated with the decision to transfer (18.2% vs. 29.8%, p = 0.294; 10% vs. 32.2%, p = 0.052). CONCLUSIONS: Neither reproductive history nor information on mosaic embryo characteristics through counselling seems to be determinative for patients when deciding to transfer a mosaic embryo. Promising and increasing data on clinical outcomes after mosaic embryo transfer will be of utmost importance to soften risk perception regarding mosaic embryos and give a better, simplified and more evidence-based counselling.

The effect of trophectoderm biopsy technique and sample handling on artefactual mosaicism.

PURPOSE: To determine whether embryo mosaicism prevalence in preimplantation genetic testing for aneuploidy (PGT-A) cycles is associated with the trophectoderm biopsy technique used (a. number of laser pulses or b. the use of flicking or pulling) or the time to tubing. METHODS: Prospective observational study performed in a single IVF-PGT-A setting from May 2019 to May 2021. Trophectoderm biopsies were analysed by next-generation sequencing. Mosaicism was analysed in relation to the biopsy methodology (number of laser pulses and pulling vs flicking), time elapsed from biopsy to tubing (min), and time of sample cryostorage from tubing to amplification (days). As a secondary objective, the number of laser pulses and biopsy methodology were studied in relation to clinical outcomes of transferred euploid blastocysts. RESULTS: None of the analysed variables were associated to mosaicism prevalence. Multivariable regression analysis demonstrated that mosaicism prevalence was comparable either when  > 3 laser pulses were used as compared to ≤ 3 (13.9% vs 13.8%, aOR = 0.8726 [0.60-1.28]) and pulling compared to flicking (13.1% vs 14.0%, aOR = 0.86 [0.60-1.23]). Moreover, neither the number of laser pulses during biopsy (> 3 vs ≤ 3) nor the technique used (pulling vs flicking) were associated with clinical pregnancy after the transfer of frozen-thawed euploid blastocysts (54.9% vs 55.2%, aOR = 1.05 [0.53-2.09]; 61.1% vs 52.9%, aOR = 1.11 [0.55-2.25], respectively). CONCLUSION: Our results suggest that, as long as the biopsy and tubing procedures are performed following standardized high quality procedures, no specific approach would increase the generation of artefactual mosaicism as a result of trophectoderm biopsy. Trophectoderm biopsies should be performed regardless of the methodology but always aiming on minimising blastocyst manipulation.

Ultrasonographic appearance of the endometrium after saline infusion in women presenting with PRM-associated endometrial changes, due to the use of ulipristal acetate.

Ulipristal acetate (UPA), used for the treatment in women with symptomatic fibroids, is associated with endometrial changes visualised on ultrasound as thickening up to more than 16 mm in approximately 10% of the patients. Is saline infusion sonography (SIS) a good alternative for more invasive techniques, to evaluate the presence of intrauterine pathology? Ten patients, presenting with UPA associated endometrial changes at their follow up ultra-sonographic evaluation, were included. Our study demonstrated that SIS is feasible and painless in patients presenting with UPA associated endometrial changes. The thickened endometrium appears to divide at the midline, making it possible to study both layers separately and exclude any suspected intrauterine pathology. Our findings suggest that SIS may be a first choice, non-invasive, painless technique to provide a proper visualisation to rule out intrauterine pathology when UPA associated endometrial changes are diagnosed after fibroid treatment. This is especially of clinical interest in front of assisted reproductive technology treatment. Invasive techniques can be withheld for patients in whom SIS examination is not contributive.Impact StatementWhat is already known on this subject? Reversible endometrial changes after ulipristal acetate (UPA) treatment in patients with symptomatic fibroids have been described. In patients who receive UPA, especially if planned to undergo ART, assessment of potential endometrial pathology is important as such interfere with proper implantation after ART. Consequently, clinicians may consider ruling out intrauterine pathology by invasive examinations such as biopsy or hysteroscopy after visualisation of the thickened endometrium.What do the results of this study add? Saline infusion sonography (SIS) was feasible and painless in patients presenting with UPA associated endometrial changes.What are the implications of these findings for clinical practice and/or further research? SIS may be a first choice, non-invasive, painless technique to provide a proper visualisation to rule out intrauterine pathology when UPA associated endometrial changes are diagnosed after fibroid treatment. This is especially of clinical interest in front of assisted reproductive technology treatment. Invasive techniques can be withheld for patients in whom SIS examination is not contributive in excluding intrauterine pathology.

Individualised luteal phase support in artificially prepared frozen embryo transfer cycles based on serum progesterone levels: a prospective cohort study.

STUDY QUESTION: Does an individualised luteal phase support (iLPS), according to serum progesterone (P4) level the day prior to euploid frozen embryo transfer (FET), improve pregnancy outcomes when started on the day previous to embryo transfer? SUMMARY ANSWER: Patients with low serum P4 the day prior to euploid FET can benefit from the addition of daily subcutaneous P4 injections (Psc), when started the day prior to FET, and achieve similar reproductive outcomes compared to those with initial adequate P4 levels. WHAT IS KNOWN ALREADY: The ratio between FET/IVF has spectacularly increased in the last years mainly thanks to the pursuit of an ovarian hyperstimulation syndrome free clinic and the development of preimplantation genetic testing (PGT). There is currently a big concern regarding the endometrial preparation for FET, especially in relation to serum P4 levels around the time of embryo transfer. Several studies have described impaired pregnancy outcomes in those patients with low P4 levels around the time of FET, considering 10 ng/ml as one of the most accepted reference values. To date, no prospective study has been designed to compare the reproductive outcomes between patients with adequate P4 the day previous to euploid FET and those with low, but restored P4 levels on the transfer day after iLPS through daily Psc started on the day previous to FET. STUDY DESIGN, SIZE, DURATION: A prospective observational study was conducted at a university-affiliated fertility centre between November 2018 and January 2020 in patients undergoing PGT for aneuploidies (PGT-A) IVF cycles and a subsequent FET under hormone replacement treatment (HRT). A total of 574 cycles (453 patients) were analysed: 348 cycles (leading to 342 euploid FET) with adequate P4 on the day previous to FET, and 226 cycles (leading to 220 euploid FET) under iLPS after low P4 on the previous day to FET, but restored P4 levels on the transfer day. PARTICIPANTS/MATERIALS, SETTING, METHODS: Overall we included 574 HRT FET cycles (453 patients). Standard HRT was used for endometrial preparation. P4 levels were measured the day previous to euploid FET. P4 > 10.6 ng/ml was considered as adequate and euploid FET was performed on the following day (FET Group 1). P4 < 10.6 ng/ml was considered as low, iLPS was added in the form of daily Psc injections, and a new P4 analysis was performed on the following day. FET was only performed on the same day when a restored P4 > 10.6 ng/ml was achieved (98.2% of cases) (FET Group 2). MAIN RESULTS AND THE ROLE OF CHANCE: Patient's demographics and cycle parameters were comparable between both euploid FET groups (FET Group 1 and FET Group 2) in terms of age, weight, oestradiol and P4 levels and number of embryos transferred. No statistically significant differences were found in terms of clinical pregnancy rate (56.4% vs 59.1%: rate difference (RD) -2.7%, 95% CI [-11.4; 6.0]), ongoing pregnancy rate (49.4% vs 53.6%: RD -4.2%, 95% CI [-13.1; 4.7]) or live birth rate (49.1% vs 52.3%: RD -3.2%, 95% CI [-12; 5.7]). No significant differences were also found according to miscarriage rate (12.4% vs 9.2%: RD 3.2%, 95% CI [-4.3; 10.7]). LIMITATIONS, REASONS FOR CAUTION: Only iLPS through daily Psc was evaluated. The time for Psc injection was not stated and no serum P4 determinations were performed once the pregnancy was achieved. WIDER IMPLICATIONS OF THE FINDINGS: Our study provides information regarding an 'opportunity window' for improved ongoing pregnancy rates and miscarriage rates through a daily Psc injection in cases of inadequate P4 levels the day previous to FET (P4 < 10.6 ng/ml) and restored values the day of FET (P4 > 10.6 ng/ml). Only euploid FET under HRT were considered, avoiding one of the main reasons of miscarriage and implantation failure and overcoming confounding factors such as female age, embryo quality or ovarian stimulation protocols. STUDY FUNDING/COMPETING INTEREST(S): No external funding was received. B.C. reports personal fees from MSD, Merck Serono, Ferring Pharmaceuticals, IBSA and Gedeon Richter outside the submitted work. N.P. reports grants and personal fees from MSD, Merck Serono, Ferring Pharmaceuticals, Theramex and Besins International and personal fees from IBSA and Gedeon Richter outside the submitted work. The remaining authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: NCT03740568.

The effect of polymorphisms in FSHR and FSHB genes on ovarian response: a prospective multicenter multinational study in Europe and Asia.

STUDY QUESTION: Does the presence of single nucleotide polymorphisms (SNPs) in the FSH receptor gene (FSHR) and/or FSH beta subunit-encoding gene (FSHB) influence ovarian response in predicted normal responders treated with rFSH? SUMMARY ANSWER: The presence of FSHR SNPs (rs6165, rs6166, rs1394205) has a statistically significant impact in ovarian response, although this effect is of minimal clinical relevance in predicted normal responders treated with a fixed dose of 150 IU rFSH. WHAT IS KNOWN ALREADY: Ovarian reserve markers have been a breakthrough in response prediction following ovarian stimulation. However, a significant percentage of patients show a disproportionate lower ovarian response, as compared with their actual ovarian reserve. Studies on pharmacogenetics have demonstrated a relationship between FSHR or FSHB genotyping and drug response, suggesting a potential effect of individual genetic variability on ovarian stimulation. However, evidence from these studies is inconsistent, due to the inclusion of patients with variable ovarian reserve, use of different starting gonadotropin doses, and allowance for dose adjustments during treatment. This highlights the necessity of a well-controlled prospective study in a homogenous population treated with the same fixed protocol. STUDY DESIGN, SIZE, DURATION: We conducted a multicenter multinational prospective study, including 368 patients from Vietnam, Belgium, and Spain (168 from Europe and 200 from Asia), from November 2016 until June 2019. All patients underwent ovarian stimulation followed by oocyte retrieval in an antagonist protocol with a fixed daily dose of 150 IU rFSH until triggering. Blood sampling and DNA extraction was performed prior to oocyte retrieval, followed by genotyping of four SNPs from FSHR (rs6165, rs6166, rs1394205) and FSHB (rs10835638). PARTICIPANTS/MATERIALS, SETTING, METHODS: Eligible were predicted normal responder women <38 years old undergoing their first or second ovarian stimulation cycle. Laboratory staff and clinicians were blinded to the clinical results and genotyping, respectively. The prevalence of hypo-responders, the number of oocytes retrieved, the follicular output rate (FORT), and the follicle to oocyte index (FOI) were compared between different FSHR and FSHB SNPs genotypes. MAIN RESULTS AND THE ROLE OF CHANCE: The prevalence of derived allele homozygous SNPs in the FSHR was rs6166 (genotype G/G) 15.8%, rs6165 (genotype G/G) 34.8%, and rs1394205 (genotype A/A) 14.1%, with significant differences between Caucasian and Asian women (P < 0.001). FSHB variant rs10835638 (c.-211 G>T) was very rare (0.5%). Genetic model analysis revealed that the presence of the G allele in FSHR variant rs6166 resulted in less oocytes retrieved when compared to the AA genotype (13.54 ± 0.46 vs 14.81 ± 0.61, estimated mean difference (EMD) -1.47 (95% CI -2.82 to -0.11)). In FSHR variant rs1394205, a significantly lower number of oocytes was retrieved in patients with an A allele when compared to G/G (13.33 ± 0.41 vs 15.06 ± 0.68, EMD -1.69 (95% CI -3.06 to -0.31)). A significantly higher prevalence of hypo-responders was found in patients with the genotype A/G for FSHR variant rs6166 (55.9%, n = 57) when compared to A/A (28.4%, n = 29), ORadj 1.87 (95% CI 1.08-3.24). No significant differences were found regarding the FORT across the genotypes for FSHR variants rs6166, rs6165, or rs1394205. Regarding the FOI, the presence of the G allele for FSHR variant rs6166 resulted in a lower FOI when compared to the A/A genotype, EMD -13.47 (95% CI -22.69 to -4.24). Regarding FSHR variant rs6165, a lower FOI was reported for genotype A/G (79.75 ± 3.35) when compared to genotype A/A (92.08 ± 6.23), EMD -13.81 (95% CI -25.41 to -2.21). LIMITATIONS, REASONS FOR CAUTION: The study was performed in relatively young women with normal ovarian reserve to eliminate biases related to age-related fertility decline; thus, caution is needed when extrapolating results to older populations. In addition, no analysis was performed for FSHB variant rs10835638 due to the very low prevalence of the genotype T/T (n = 2). WIDER IMPLICATIONS OF THE FINDINGS: Based on our results, genotyping FSHR SNPs rs6165, rs6166, rs1394205, and FSHB SNP rs10835638 prior to initiating an ovarian stimulation with rFSH in predicted normal responders should not be recommended, taking into account the minimal clinical impact of such information in this population. Future research may focus on other populations and other genes related to folliculogenesis or steroidogenesis. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by an unrestricted grant by Merck Sharp & Dohme (MSD). N.P.P. reports grants and/or personal fees from MSD, Merck Serono, Roche Diagnostics, Ferring International, Besins Healthcare, Gedeon Richter, Theramex, and Institut Biochimique SA (IBSA). N.L.V. and M.T.H. report consultancy and conference fees from Merck, Ferring, and MSD, outside the submitted work. P.D. has received honoraria for lecturing and/or research grants from MSD, Ferring International, and Merck. D.S. reports grants and/or personal fees from MSD, Ferring International, Merck Serono, Cook, and Gedeon Richter. A.R.N., B.A.M., C.S., J.M., L.H.L., P.Q.M.M., H.T., and S.G. report no conflict of interests. TRIAL REGISTRATION NUMBER: NCT03007043.

Prevalence, types and possible factors influencing mosaicism in IVF blastocysts: results from a single setting.

RESEARCH QUESTION: Are intrinsic or extrinsic factors associated with embryo mosaicism prevalence in IVF cycles? DESIGN: Retrospective cohort study of preimplantation genetic testing for aneuploidy (PGT-A) cycles carried out at a university-affiliated IVF clinic between October 2017 and October 2019. Trophectoderm biopsies were analysed by next generation sequencing. Mosaicism prevalence, type of anomaly and the chromosomes involved were analysed. Intrinsic and extrinsic factors potentially inducing mosaicism were studied: maternal and paternal age, antral follicle count, cumulus-oocyte complexes retrieved, female body mass index, PGT-A indication, sperm concentration, total dosage of gonadotrophins, embryo quality and day of blastocyst formation, single-step commercial media used and biopsy operator. RESULTS: Overall prevalence of mosaicism in our PGT-A setting was 13.9%. In segmental mosaicism, larger chromosomes tended to be more affected, which was not observed in whole-chromosome mosaicism. Additionally, segmental mosaicism was mostly observed in monosomy (69.6%; P < 0.01) compared with whole-chromosome mosaicism (49.7% monosomies versus 50.3% trisomies; P = 0.83). Although a high inter-patient variability was observed, only paternal age showed a positive association with mosaicism (adjusted OR 1.26, 95% CI 1.02 to 1.54) among the analysed variables. CONCLUSIONS: Our results suggest remarkable differences in the mechanisms generating segmental and whole-chromosome mosaicism, indicating that they may deserve different consideration when studying them and when prioritizing them for transfer. Male factor seems to be associated with mosaicism and may be worthy of specific assessment in future studies.