2PN Embryos Research Articles

Effect of body mass index on ovarian reserve and ART outcomes in infertile women: a large retrospective study

BackgroundObesity poses a significant global health challenge, with profound implications for women’s reproductive health. The relationship between ovarian reserve and body mass index (BMI) remains a subject of debate. While obesity is generally associated with poorer outcomes in assisted reproductive technology (ART), the evidence remains inconclusive. This study aimed to investigate the effect of pre-pregnancy BMI on ovarian reserve and ART outcomes in infertile patients.MethodsWe conducted a retrospective cohort study involving women who underwent in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) procedures at Tongji Hospital between 2016 and 2023. The study included 30,746 initial fresh cycles and 5,721 singleton deliveries. Patients were stratified by age and further categorized into four BMI groups: lean (< 18.5 kg/m²), normal weight (18.5–24.9 kg/m²), overweight (25.0–29.9 kg/m²), and obese (≥ 30.0 kg/m²). The primary endpoints of the study were pregnancy and perinatal outcomes. To explore the association between BMI and these outcomes, we adjusted for relevant confounding factors and utilized multivariate linear regression models, complemented by multifactorial logistic regression analyses.ResultsAnti-Müllerian hormone (AMH) levels were significantly lower in the overweight and obese groups compared to the normal weight group. After adjusting for age, a negative correlation was found between AMH and BMI in the age subgroups of 20–30 and 30–35 years. Among women aged 20–35 years, those in the overweight and obese groups had significantly fewer retrieved oocytes, mature oocytes, and two-pronuclear (2PN) embryos than their normal weight counterparts. Despite these differences, pregnancy outcomes in the overweight and obese groups were comparable to those in the normal weight group across all age categories. Additionally, obesity was linked to an increased risk of gestational diabetes mellitus, hypertensive disorders of pregnancy, and macrosomia.ConclusionsAn age-related decrease in AMH levels was evident with increasing BMI. Although being overweight or obese is associated with poorer embryo and perinatal outcomes, it does not seem to have a substantial impact on fertility.

Use of time-lapse technology on fertilization verification, embryo evaluation, and utilization: A national survey in Japan

BackgroundTime-lapse technology (TLT) has emerged as a significant advancement in the field of assisted reproductive technology (ART), providing continuous observation of embryos. However, limited information exists on the adoption of TLT across ART facilities and the clinical implications of its application in embryo evaluation and fertilization verification. The existing literature has not yet comprehensively examined how TLT data are utilized to optimize ART outcomes, particularly in Japan, where ART practices are highly prevalent. ObjectivesThis study aimed to investigate the adoption rate of TLT and its clinical effects on fertilization verification, embryo evaluation, and utilization of ART in Japan. Study DesignAn online survey was conducted from December 23, 2022, to January 16, 2023, in 616 ART facilities with both email and mailed notices. The survey investigated the utilization of TLT in each facility's evaluation of oocyte morphology, fertilization, embryo culture, and morphology. ResultsOverall, 345 responses were analyzed. Of these, only 42.6% confirmed fertilization at 16 to 18 hours after insemination. Most facilities defined normally fertilized eggs as 2 pronuclei (2PN; 53.3%) or a combination of a second polar body extrusion and 2PN (44.9%). Overall, 54.6% of the facilities had adopted TLT, and 76.9% to 96.9% of these facilities used TLT images for fertilization verification. At these centers, the use of 0PN embryos decreased, whereas the use of 2.1PN embryos increased. The rates of culture medium supplemented with antioxidants and hyaluronan were significantly higher in facilities with TLT than in those without TLT. TLT images were used for embryo evaluation in 94.3% of the facilities, while 31.0% used a combination of TLT images and artificial intelligence-based scoring systems. ConclusionsWhile TLT use is widespread in Japan, its application in evaluating fertilization and embryo development stages varies across facilities. Reaching a consensus on the optimal use of the TLT system will enhance the effectiveness, safety, and efficiency of ARTs.

P-142 The developmental time to reach the blastocyst stage in the human is an indicator of diploid mono-pronuclear embryos

Abstract Study question Is it possible to determine diploid mono-pronuclear (1PN) human embryos by the speed of development to blastocyst formation? Summary answer The developmental time to reach the blastocyst stage is a discrimination indicator for diploid 1PN embryos. What is known already We have previously reported that 80.7% of 1PN zygotes had a biparental chromosome using a Live-Cell imaging technique, and some of these developed to the blastocyst stage (Tokoro et al. ASRM 2013). Furthermore, we have reported that these blastocysts can result in a healthy live birth (Tsuji et al. ASRM 2020), and there was no effect on growth up to 5 years of age (Tsuji et al. ASRM 2023). On the other hand, it was also shown that a few of the 1PN embryos that developed into blastocysts were haploid embryos. Study design, size, duration This was a retrospective study that included 28 blastocysts derived from a 1PN zygote. The time period was 72 months (January 2017 to December 2022). These embryos are used for research following obtaining informed consent. Participants/materials, setting, methods The frequency rate of diploid embryos was compared from time of PN fading to blastocyst formation (Gardner’s classification: ≥ expansion grade 3). Two development time range groups were examined and designated: fast-developing embryos (65.7-78.7h) and slow-developing embryos (116.8-139.7h). Ploidy status was determined using whole blastocyst cells and NGS-based SNP analysis. Statistical significance was determined using Fisher’s exact test (level of P&amp;lt;0.05). Main results and the role of chance There was no significant difference in the average age (years) of the two development time groups (fast-developing embryos group; 35.5 +/- 5.5, slow-developing embryos group; 34.1 +/- 2.8). The frequency of diploid status in 1PN embryos with fast developing embryos was 100% (14/14), and in 1PN embryos designated as having slow development, the frequency of diploid embryos was only 14.3% (2/14), haploid embryos 71.4% (10/14), and other was 14.3% (2/14). As a result, the diploid embryo rate was significantly higher in fast-developing embryos than in slow-developing embryos (P&amp;lt;0.001). Limitations, reasons for caution This study was limited to extremely fast or slow-developing embryos to see trends. It is important to study the threshold time between diploidy and haploidy in 1PN embryos. Wider implications of the findings These results confirmed that fast developing 1PN embryos have a high diploid rate and can be used as transferable embryos in addition to 2PN embryos. Conversely, slow developing 1PN embryos should be considered to have a lower priority for transfer because of the high rate of haploid embryos. Trial registration number not applicable

P-514 Unequal pronucleus size is indicative of higher rates of diploidy in 3PN blastocysts

Abstract Study question What proportion of blastocysts developed from 3PN embryos are diploid, and is this associated with the relative size of the pronuclei? Summary answer Most 3PN blastocysts with even-sized pronuclei are triploid, while most 3PN blastocysts with uneven-sized pronuclei are diploid. What is known already Fertilised oocytes with three pronuclei (3PN, or tripronuclear) are generally considered unsuitable for use due to the high likelihood of triploidy, which is not compatible with an ongoing healthy pregnancy. Recent data on 3PNs with uneven-sized pronuclei (micro-3PN, or 2.1PN) indicates that many may actually be diploid if they form a good quality blastocyst. Study design, size, duration Prospective multi-centre study from October 2020 to December 2023. 81 3PN blastocysts from 69 patients were biopsied. Participants/materials, setting, methods ICSI-inseminated embryos were assessed on Day 1 and pronuclear size at 18 h post insemination was measured using EmbryoViewer software. Biopsy was performed at the blastocyst stage and genetic testing was performed using the Human Karyomap-12 SNP array to ascertain ploidy status. Pronuclei were classified as “Equal”, “Unequal” (smallest pronucleus is 61%-75% of the largest), or “Micro” (smallest pronucleus is &amp;lt; 60% of the largest). Main results and the role of chance 94% of the 3PN blastocysts with equal size pronuclei were triploid, and the remaining 6% were complex aneuploid or had genome wide uniparental disomy (n = 36). Of the 3PN blastocysts with unequal pronuclei (n = 19), 42% were triploid, whereas none of the embryos with a micro pronucleus were triploid (n = 26). Limitations, reasons for caution Only 3PN embryos that formed a good quality expanded blastocyst were biopsied. Only ICSI-inseminated embryos were included, not IVF. No 3PN embryos were transferred in the study, so any additional pregnancy and birth risks from diploid 3PN embryos are unknown. Wider implications of the findings Blastocysts that develop from 3PN oocytes with uneven pronuclei have a greater than 80% chance of diploidy and could be considered for clinical use with PGT. More data is needed to inform clinical guidelines. Trial registration number N/A

P-232 EIF4E1B Contributes to Early Translation Burst for Embryogenesis Whose Deficiency Causes Embryo Development Arrest at Four-Cell Stage during Oocyte to Embryo Transition in Women

Abstract Study question What are the effects and corresponding mechanisms of the early burst of translation inhibited during the oocyte-to-embryo transition (OET), which is essential for human embryogenesis? Summary answer EIF4E1B contributes to the early burst of translation for embryogenesis whose deficiency causes embryo development arrest at four-cell stage during OET in women. What is known already The first records of human zygotic genes are observed in late one-cell zygotes, and translation in mammals happens before the activation of zygotic genes. Recently, we identified an oocyte specific role of eIF4E1b in selecting and regulating the translation initiation of individual mRNAs that are involved in cell differentiation, cell cycle regulation, and cell fate determination during OET. The genetic ablation of Eif4e1b in mice resulted in a developmental arrest in the 2-cell phase of embryogenesis. How is the early burst of translation regulated in human embryogenesis remains unknown. Study design, size, duration A total of 236 female Chinese participants who underwent assisted reproductive technology (ART) and experienced at least one cycle of OET defects were recruited from our university-affiliated center from January 2017 to May 2023. 60 frozen human 3 pronuclei (3PN) embryos have been used for this work. The use of human embryos donated for research was allowed by the the Ethics Committee of the Reproductive and Genetic Hospital of CITIC–Xiangya (reference LL-SC-2018-009). Participants/materials, setting, methods All recruited individuals underwent whole-exome sequencing. In vitro transcription and micro-injection were employed to validate the embryo development pattern under different translation inhibition as well as potential effects of the EIF4E1B variant in mouse oocytes. Immunoprecipitation was conducted to investigate the causes of OET failure and identify the ability of eIF4E1B bind with PABPC1L. Additionally, a knock-in (KI) mouse model carrying homozygous Eif4e1bA192T was generated to evaluate female fertility and a more comprehensive mechanism. Main results and the role of chance Translation inhibitor cycloheximide (CHX) and knockdown of different translation initiation factors eIF4Es were administered to human 3 pronuclei (3PN) embryos, starting from the 1C stage. The absence of eIF4E1B was identified as a specific phenotype, leading to developmental arrest at the 1-4C stage, which is consistent with the effects of Translation inhibitor CHX. Additionally, a novel homozygous mutation (c.565G&amp;gt;A; p. Ala189Thr) in EIF4E1B was found within a consanguineous family. This mutation was associated with recurrent four-cell arrests, suggesting a translational regulation role for eIF4E1B from the 1C to 4C stage during OET. The mutated eIF4E1B disrupted the expression and condensate distribution of eIF4E1B. We also confirmed the interaction between eIF4E1B and PABPC1L, with the c.565G&amp;gt;A variant in EIF4E1B impairing their binding ability. Furthermore, KI mice carrying homozygous Eif4e1bA192T partially recapitulated the phenotype resulting from EIF4E1B deficiency. Limitations, reasons for caution More cases are required to demonstrate the association between EIF4E1B variants and phenotypes. Wider implications of the findings By delving deeper into the intricate interactions between basic physiology and clinical characteristics, this research elucidates the crucial role of maternal EIF4E1B in ensuring the early burst of translation for embryogenesis and provide a diagnostic genetic marker for women with OET defects. Trial registration number Not applicable

O-184 Piezo-ICSI reduces oocyte degeneration, improves ICSI success rates and has shown less dependence on the experience level of embryologists: cumulative data with 65,033 MII oocytes

Abstract Study question Dose piezo-ICSI improve the overall success rates of in ICSI operations compared with the conventional ICSI by the operators with different level of experience? Summary answer Piezo-ICSI showed lower oocyte degeneration rate during or after ICSI operations compared to the conventional ICSI for embryologists with different level of experience. What is known already Intracytoplasmic sperm injection (ICSI) with a glass micropipette can sometimes result in degeneration of the injected oocyte. Piezo-assisted ICSI has been developed as an alternative method to prevent such degeneration occurring during the procedure. It employs gentler and controlled impacts generated from the piezo electric elements attached to the injection micropipette holder to penetrate oolemma, and it does not require reciprocal aspiration of ooplasm required in the conventional ICSI. While there have been numerous study reports demonstrating the improvements in fertilization rates with piezo-ICSI, most of these studies have the limitation in the size study of population. Study design, size, duration We conducted a retrospective analysis of the ICSI results with 65,033 MII oocytes in 15,687 treatment cycles carried out between January 2018 and February 2023. ICSI were performed using the piezo-assisted equipment with flat-tip micropipettes (PIEZO PMM4G, Prime Tech Ltd., [n = 51,484, Piezo-group]) or in the conventional ICSI method with spiked-tip micropipettes (n = 13,549, C-group). Participants/materials, setting, methods Following the insemination with ICSI, the oocyte degeneration rate, fertilization rate per MII oocytes and blastocyst formation rate per 2PN embryos were evaluated in both the Piezo- and C-groups (n = 51,484 and n = 13,549, respectively). We also evaluated the degeneration rates and fertilization rates of ICSI by the operators: i.e., well-experienced embryologists (at least 10 years of experience) and less experienced embryologists (5 years or less of experience). Main results and the role of chance The fertilization and blastocyst formation rates in the Piezo-group were 83.8% (43,140/51,484) and 54.0% (23,300/43,140), respectively, which were significantly higher than the C-group (74.8% [10,132/13,549] and 36.6% [3,674/10,132], respectively, p &amp;lt; 0.01). The oocyte degeneration rate in the Piezo-group was 2.9% (1,493/51,484), which was significantly lower than the C-group (6.9% [933/13,549], p &amp;lt; 0.05). For the patients over 40 years old, the degeneration rate was also significantly lower in the Piezo-group (3.0% [632/20,770]) than the C-group (7.1% [351/4927], p &amp;lt; 0.01), while the fertilization and blastocyst formation rates were higher in the Piezo-group (82.6% [17,164/20,770] and 46.6% [7,997/17,164], respectively) than the C-group (72.8% [3,588/4,927] and 25.8% [926/3,588], respectively, p &amp;lt; 0.01). We found a marked drop in the oocytes degeneration rates in the Piezo group recorded from both well-experienced and less experienced embryologists. The degeneration rates recorded by less experienced embryologists were 2.8% (119/4,242) in Piezo-group and 8.6% (8/93) in the C group (p &amp;lt; 0.01), while the records by well-experienced embryologists were 2.7% (815/29,681) in the Piezo-group and 6.9% (555/8,037) in the C-group, respectively (p &amp;lt; 0.01). The fertilization rates of the Piezo-group by less experienced and well-experienced embryologists were 84.1%(3,569/4,242) and 83.4% (24,757/29,681), respectively, which were significantly higher the C-group (71.0％ [66/93] and 76.7％ [6,167/8,037], respectively, p &amp;lt; 0.01). Limitations, reasons for caution It is a retrospective study, in which the ICSI operations with piezo and the conventional methods were not equally assigned to the embryologists, especially, for those less experienced, thereby the number of conventional ICSI operations was more skewed to well-experienced embryologists than the less experienced colleagues. Wider implications of the findings Our results with piezo-ICSI showed a marked drop in the oocyte degeneration while achieving comparable fertilization rates amongst operators with different levels of experience. We found these as major advantages over the conventional method in standardizing the ICSI operation by filling the gap between embryologists with different length of carrier. Trial registration number Not applicable

O-065 PGT-A reveals triploid embryos among normally fertilized oocytes: Frequency and blastocyst features

Abstract Study question Is there any embryo parameter that could differentiate 2 pronucleus (PN) triploid from 2 PN euploid embryos? Summary answer Accuracy in the fertilization check is still necessary as 2 PN but triploid embryos are due mostly to retention of the second polar body (PB). What is known already Since blastocyst culture has evolved and the development of genetic technologies enables to know the karyotipe of the embryos, the concept of normal fertilization is being revised. Commonly, correct fertilization is denoted by the appearance of 2 PN 16-18h after insemination. Deviation from 2PN is considered evidence of abnormal fertilization and ploidy anomalies. However, not all oocytes exhibiting 2 PN are euploids. After performing NGS in trophectoderm biopsies for preimplantation genetic testing for aneuploidy (PGT-A), a percentage of embryos are categorized as triploids. Study design, size, duration Retrospective study including 1862 cycles from 1605 patients aged 18-45 years old who underwent PGT-A with NGS of trophectoderm biopsies in our IVF center from 2019 to 2023. From 6526 analyzed blastocysts in an independent Genetics laboratory, 59 were categorized as triploids. These 59 blastocysts were obtained from 57 PGT-A cycles and belonged to 54 women. In total, these patients had 266 biopsied blastocysts. From the remaining 207 embryos, 42 were called as euploids. Participants/materials, setting, methods In embryos cultured in time-lapse, fertilization was re-evaluated to check the appearance of 2PN and the second PB extrusion. Genetic triploid embryos were analysed in relation to the day of biopsy (day 5 vs day 6), the trophectoderm quality and the timing of the first cell divisions (time of cleavage from 2 to 6 cells: t2, t3, t4, t5, t6). Categorical variables are shown as rate. T-student tests were performed. P-value&amp;lt;0.05 was considered statistically significant. Main results and the role of chance The re-evaluation of the fertilization of the 59 triploids categorized as 2 PN revealed 50 oocytes 2 PN, 8 embryos 3 PN and 1 embryo 2 PN + 1 micronuclei configuration. Therefore, the prevalence of real triploidy in 2PN embryos was 0,8% (n = 50/6526; CI95%:0,6-1,0%). These data showed that 2PN zygotes may give rise to embryos with altered ploidy. From 27 triploid 2PN embryos was possible to access to the whole development time-lapse images. Just 33,3% of triploid embryos exhibited the extrusion of the second PB, while 100% of euploid sibling embryos showed this extrusion (N = 9/27 vs N = 24/24,;p&amp;lt;0,005). Comparing 2 PN triploid and the rest of the embryos from the same cohorts, there were no differences regarding the day of biopsy (N = 31/176 day 5 biopsy, 17.6% vs N = 19/81 day 6 biopsy, 23.5%; p &amp;gt; 0.05). On the contrary, a worse blastocyst quality showed a significant relation with triploidy (N = 23/161,14,2% of good quality embryos are triploid vs N = 27/96, 38,6% of fair quality embryos are triploids; p:0.006).Embryos cleavage time points up to 6-cell stage did not show any significative difference between triploid and euploid embryos (t2: 27.36h vs 25.8h; t3: 38.5h vs 35.6h; t4 39.4h vs 37.2h; t5 52.8h vs 47.0h; t6 56.2h vs 52.1h; all comparisons p &amp;gt; 0.05). Limitations, reasons for caution The incidence of triplody from 2PN zygotes may vary among IVF laboratory settings. The small sample size may be responsible of no difference in morphokinetics. Wider implications of the findings Fertilization check should persist in IVF procedures. Special consideration should be given to the second PB extrusion as triploidy is the most common form of aneuploidy observed in the first trimester miscarriages. The role of diploid spermatozoa, the size of the pronucleus and location should be explored in further studies. Trial registration number NOT APPLICABLE

O-006 Oocyte factors as predictors of abnormal, mononucleated and trinucleated, zygotes and assessment of their morphokinetic differences

Abstract Study question Are there oocyte factors associated with the occurrence of mononucleated and trinucleated zygotes after ICSI? Does morphokinetics differ in embryos from normal and abnormal zygotes? Summary answer Formation of 1PN zygotes relates to vitrificated and donor oocytes. 3PN links to age and own oocytes. 1PN embryo morphokinetics are slower than 2PN, 3PN. What is known already In assisted reproduction, after monitoring fertilization, it is common to observe zygotes with one or more than 2 pronuclei. These abnormal zygotes are often discarded due to potential chromosomal abnormalities. The formation of these anomalous zygotes can be attributed to various causes, such as non-activation of the male pronucleus, non-extrusion of the second polar body, etc. Simultaneously, limited data exist on the morphokinetics of abnormal zygotes, explored in a few studies. The embryonic kinetics of 1PN zygotes seem slower than those of 2PN and 3PN zygotes, but further research is needed to confirm this aspect. Study design, size, duration Retrospective multicentre study involved time-lapse monitoring of 28,218 ICSI zygotes (26,252 2PN, 1,190 1PN, and 776 &amp;gt;3PN) generated between January 2019 and December 2023. The study includes donor and patient oocytes with various infertility diagnoses, whether fresh or vitrified. The comparison of embryonic morphokinetics from abnormal/normal zygotes was conducted on 254 embryos from a single centre, with 45 originating from 1PN zygotes, 198 from 2PN zygotes, and 11 from zygotes with 3 or more pronuclei. Participants/materials, setting, methods The study involved 1,053 couples treated in four different centres. Uniform culture media were used, and oocytes were cultivated in time-lapse technology-equipped incubators across all centres. A logistic regression analysis aimed to identify oocyte factors linked to an abnormal pronuclei count. Embryonic morphokinetics were analysed using the CHLOE artificial intelligence system (Fairtility, Israel). Evaluated parameters included: tPNa, tPNf, t2, t3, t4, t5, t6, t7, t8, t9+, tM, tSB, tB, and tEB. Main results and the role of chance Donor oocytes exhibited a 1.32 times higher risk of producing 1PN zygotes than 2PN or 3PN zygotes (p &amp;lt; 0.001). Similarly, vitrified oocytes had a 1.63-fold higher risk of generating 1PN zygotes than 2PN or 3PN zygotes (p &amp;lt; 0.001). Additionally, we found that both the use of own oocytes and advanced age were significantly associated with 3PN zygotes (p &amp;lt; 0.001). Regarding age, the risk increases by 10% for each additional year. The average durations for all morphokinetic parameters of 2PN and 3PN embryos were similar. In contrast, all events, except t3 (p = 0.2), occurred more slowly in embryos derived from 1PN zygotes compared to embryos from 2PN zygotes. Thus, the disappearance of pronuclei had a p-value &amp;lt;0.005, and from t4 to tEB, the p-value was &amp;lt;0.001. When comparing embryos from 1PN and 3PN zygotes, only tPNa, t4, t8, t9+, and tM were significantly different. If only zygotes that reached the blastocyst stage were used for analysis, the results were less conclusive due to a significantly reduced number of cases. Limitations, reasons for caution Embryos were cultured in an EmbryoScope incubator at three centres, while Geri was used in the fourth. Wider implications of the findings Using donor or vitrified oocytes may lead to an increased occurrence of zygotes with 1PN, as will occur with 3PN when patient or aged oocytes are used. The kinetics of embryos from 3PN oocytes resemble those from 2PN, while those from 1PN zygotes exhibit slower kinetics. Trial registration number not applicable

O-214 The effect of constant 5% versus gradient 8%, 5%, 2% oxygen concentration on the development of sibling human embryos in vitro to the blastocyst stage

Abstract Study question Does a physiological gradient of oxygen concentration in embryo culture atmosphere yield a higher percentage of fertilized oocytes developing into morphologically optimal blastocysts? Summary answer Study favours sustaining a static 5% oxygen level, instead of a gradient, during extended embryo culture, resulting in more viable embryos for cryopreservation and transfer. What is known already To date, there’s ongoing research about the optimal oxygen concentration for embryo culture. The available data from studies based on animal models show that the O2 level in the fallopian tube is around 8%, and the in-utero O2 level is at around 2% (Wale &amp; Gardner, 2010). Data on oxygen measurement in the human uterus is scarce, yet aligns with similar findings in other mammalian species (Ng et al., 2018). These findings support the use of sequential O2 levels for embryo culture. Our study stands as the first to implement such dynamic oxygen culture conditions within an in vitro setting. Study design, size, duration A prospective sibling-split oocyte study, analyzing 44 ICSI cycles from January 2022 to January 2023, with alternate allocation into a static 5% (Control group) during entire culture period or under an oxygen gradient (intervention group), starting with 8% from day-0 to day-3, continuing with 5% on day-3 and following with 2% of oxygen from the end of day-3 to day-5/6. Participants/materials, setting, methods 44 ICSI cycles, which produced a total of 521 metaphase II oocytes. A total of 353 2PN embryos were cultured and annotated in time-lapse for morphokinetic and morphometric analysis. Main results and the role of chance While morphological outcomes slightly favored the intervention group for day 2 and day 3 embryos, the trend reversed by day 5. The control group (5% O2) showed a notably higher proportion of zygotes developed to clinically utilized blastocysts (47% vs. 37%, p = 0.016) and consequently more of them were used for transfer on day 5 (10% vs. 4%, P = 0.008) compared to the intervention group. Additionally, though not statistically significant, the control group showed a higher percentage of morphologically optimal blastocysts on day 5 (10.3% vs. 14.7%, p = 0.1233). Morphokinetic timings, as revealed by time-lapse analysis, indicated a delayed development in the intervention group, notably seen in the initiation of blastulation (p = 0.0024), initiation of expansion (p &amp;lt; 0.0001), and full blastocyst formation (p &amp;lt; 0.0001). The speed of blastulation, however, does not necessarily reflect differences in implantation potential, as implantation (58.6% vs 57.1% p &amp;gt; 0.92) and clinical pregnancy rates (55.2% vs 57.1%, p &amp;gt; 0.92) after transferring blastocysts from either group were comparable. Limitations, reasons for caution Measuring the in vivo O2 levels in female reproductive tract should take into account possible oscillations and dynamic nature of gas and nutrient exchange. It’s also important to acknowledge the complexity of embryo’s adaptive response, making it challenging to attribute observed outcomes solely to the impact of targeted oxygen concentration. Wider implications of the findings Based on these clinical results, we will analyze the metabolomic footprint in spent embryo culture under static 5% or gradient 8-5-2% oxygen concentration, employing non-invasive NMR and chromatography methods. A randomized control trial should be conducted to explore the effect of different oxygen regimes on clinical outcomes. Trial registration number NCT05898178

P-151 Investigation of pregnancy outcomes for blastocysts with microcellular leakage of trophectoderm or inner cell mass from ICSI-induced zona pellucida microslits

Abstract Study question How does ICSI-induced leakage of trophectoderm (TE) or inner cell mass (ICM) from microslits in the zona pellucida (ZP) affect pregnancy outcomes following blastocyst transfer? Summary answer Microcellular leakage of TE and ICM did not affect pregnancy outcome, but blastocysts with ICM leakage above 53.6% had a lower pregnancy rate. What is known already The leakage of TE cells through the ZP (trophectoderm vesicles; TV) has been reported to be more common in ICSI than in conventional IVF, caused by the opening of the ZP with microslits for ICSI. This phenomenon may be improved through the implementation of assisted hatching during transplantation, however, there are few reports investigating its impact on pregnancy.Furthermore, there are no reports on the impact of inner cell mass leakage (inner cell mass vesicles; IV) on pregnancy outcomes, and it is unclear what level of ICM leakage is acceptable for transplantation. Study design, size, duration In this retrospective study, we analyzed clinical medical reports at the Takahashi Women’s Clinic in Japan. A total of 551 patients (1093 blastocysts) who underwent freeze-thaw single blastocyst transfer with laser assisted hatching between January 2019 and October 2023 were included. Blastocysts used for transfer were 2PN embryos obtained by PIEZO-ICSI and cultured in a time-lapse incubator (EmbryoScope+). Participants/materials, setting, methods The blastocysts were classified into control (N = 682), TV (N = 377), and IV groups (N = 34). Pregnancy outcomes were compared using logistic regression analysis, considering patient age, blastocyst grade (Gardner criteria), culture days, BMI, and basal AMH. Bonferroni correction was used for multiplicity correction, considering P &amp;lt; 0.0167 as significant. The ICM leakage rate (%) was calculated as: (leaked ICM area/ICM area before leakage) × 100. Pregnancy cutoff was determined by ROC analysis. Main results and the role of chance The hatching rates for the control, TV, and IV groups were 69.6% (475/682), 78.8% (297/377), and 82.4% (28/34), respectively. Pregnancy rates (fetal heartbeat) were 44.6% (304/682), 57.0% (215/377), and 50.0% (17/34), respectively, and miscarriage rates were 26.3% (80/304), 26.0% (56/215), and 23.5% (4/17), respectively. Logistic regression analysis considering patient background showed no significant differences in hatching, pregnancy, and miscarriage rates (P &amp;gt; 0.05). Furthermore, mean weight, sex ratio, and congenital anomaly rates for the 107 and 7 children born in the TV and IV groups, respectively, were not significantly different than those for the 175 children born in the control group. In examining ICM leakage, the mean area before leakage was 3162.6 µm2 and mean area of leaked ICM was 1292.1 µm2 in the IV group, with an average of 40.9% of ICM leaking outside the clear zone. ROC analysis showed that the cutoff for ICM leakage rate for pregnancy was 53.6%, with significantly lower pregnancy rates when the ICM leakage rate was ≥53.6% (18.2% [2/11] vs 65.2% [15/23], p = 0.0255, Fisher’s exact test). Limitations, reasons for caution This study was conducted at a single in vitro fertilization center. Pregnancy, miscarriage, and fetal anomaly rates at birth related to embryo transplantation are based on ongoing pregnancy dates, and complete live birth data for all pregnancies are not yet available. Wider implications of the findings No differences in pregnancy outcomes or fetal anomalies were found among groups. However, pregnancy rates decreased when ICM leakage rates were over 53.6%. Blastocysts with IV may successfully establish a pregnancy, but considering the leaked ICM proportion is crucial. If considered for transplantation, obtaining sufficient informed consent is essential. Trial registration number not applicable

P-113 Comparison of mitochondrial function between expanded and hatching human blastocysts

Abstract Study question Is there a difference in mitochondrial function between expanded and hatching fresh and vitrified blastocysts? Summary answer Freezing and thawing may lead to mitochondrial dysfunction. What is known already Mitochondria, as crucial cellular organelles, play role in energy production through the electron transport chain, cell motility and organelle movement. They also have a significant impact on embryonic development. Furthermore, during the process of embryonic hatching, the energy generated by these organelles can affect ion pump activity, blastocyst expansion, and collapse. Therefore, factors that stress embryonic mitochondria may contribute to embryogenesis and hatching. Cooling and warming, as stress factors, maybe result in organelle damage, protein denaturation, membrane disruption, and DNA fragmentation. Additionally, they can cause changes in mitochondrial function, leading to decreased ATP levels and increased ROS levels. Study design, size, duration In this study, vitrified and fresh human 8-cell embryos were collected from April 18, 2021, to July 19, 2023. The embryos were cultured until the blastocyst stage, and then four samples were assessed in four groups. These groups included vitrified expanded blastocysts, vitrified hatching blastocysts, fresh expanded blastocysts, and fresh hatching blastocysts. Participants/materials, setting, methods Vitrified embryos were sourced from the embryo bank of the Royan Institute, while fresh embryos were obtained from good-quality 3PN embryos or excess embryos from couples who did not wish to freeze them. A stock solution containing lipophilic cationic JC-1 dye in dimethyl sulfoxide was prepared. Blastocysts were then exposed to a concentration of 1 μg/ml of JC-1 diluted in HamsF10-HSA. After washing with HF-HSA, imaging was performed using a 2-photon confocal microscope. Main results and the role of chance Our results showed that mitochondrial membrane potential in expanded blastocysts of both fresh and vitrified eight-cell embryos was significantly higher than in hatching blastocysts of fresh and vitrified embryos (P &amp;lt; 0.05). However, there was no significant difference in mitochondrial function between the vitrified and fresh groups, neither in expanded nor hatching blastocysts. Limitations, reasons for caution Due to the human origin of the samples, the minimum necessary replicates were considered for each experimental group. Wider implications of the findings In this study, it appears that plump zona breakers can be detected in hatching blastocysts using confocal microscopy. Previous studies, such as the one conducted by Sathananthan, identified these cells using a TEM microscope. Trial registration number -

O-215 Copper oxide nanoparticles (CuONPs) impairs mitophagy and promotes DNA methylation to suppress mouse embryonic pluripotency

Abstract Study question Does exposure to copper oxide nanoparticle (CuONPs) have adverse effects on early embryonic development? What is the potential mechanism? Summary answer CuONPs exposure can damage mitophagy and lead to α-KG reduction, resulting DNA hypermethylation, thereby reducing the pluripotency of pre-implantation embryos in mice. What is known already Environmental nanomaterials contamination is a great concern for organisms including human. Exposure to nanomaterials have been associated with fecundity and fertility in couples conceiving via assisted reproduction technology. Among these bio-effects, nanomaterials induced epigenetic changes are of particular interest. Copper oxide nanoparticles (CuONPs) are widely used in a huge range of applications which might pose potential risk to organisms. Recent studies reported that CuONPs exposure resulted in transgenerational toxicity in Caenorhabditis elegans associated with possible epigenetic regulation. However, whether CuONPs exposure affect mammalian embryonic development, and if so the underlying mechanisms, are unclear. Study design, size, duration For the human experiments, we measured the copper ion content in women’s urine, and assessed the expression of pluripotent genes in 3PN embryos treated with CuONPs. For the embryo experiments, we collected zygotes from ICR mice and cultured them in KSOM medium with CuONPs (10 μg/mL) until blastocyst stage. For the cell experiments, we treated mouse embryonic stem cells (mESCs) with CuONPs (2 μg/mL) for four days to detect cell proliferation and pluripotency. Participants/materials, setting, methods The ICP-MS method was used to detect copper ion content in women’s urine. Time–lapse incubator was used to document the developmental potential of embryos. To quantify the metabolites of embryo, we employed metabolomics. Single-cell multiomics sequencing that enables profiling of genome-wide chromatin accessibility, DNA methylation and RNA expression were performed to detect genes expression and epigenetic modification. We used real-time PCR, immunofluorescence, and western blot to measure the expression of pluripotency related genes. Main results and the role of chance In human, we discovered a significant negative relationship between the urine’s copper ion content and clinical pregnancy rate. In embryo experiments, CuONPs exposure has been shown to have adverse effects on embryo developmental potential, resulting morula and blastocyst transformation arrest, as well as reduction in blastocyst rate and live birth rate. Furthermore, CuONPs treatment led to a reduction in blastocyst quality, indicating a decrease in blastocyst cell count, particularly in ICM cells. CuONPs also inhibited the pluripotency of blastocysts and mESCs, showing down-regulated expression of pluripotent genes. Mechanistically, CuONPs aggregated in lysosomes and decreased the mitophagic flux of embryos, which caused damaged mitochondria to accumulate and ultimately caused mitochondrial dysfunction. Notably, in embryos treated with CuONPs, there was a decrease in α-ketoglutarate (α-KG) due to the disruption of the tricarboxylic acid (TCA) cycle. α-KG is an essential cofactor for α-KG dependent dioxygenases such as the ten-eleven translocation (TET) family of DNA demethylase. The lack of α-KG in CuONPs-treated embryos led to DNA hypermethylation, which reduced chromatin accessibility, and suppressed the expression of pluripotent genes like sox2, klf2, and klf4. The poor pluripotency ultimately leads to abnormal embryonic development in CuONPs-treated embryos. Limitations, reasons for caution The molecular mechanism by which CuONPs arrest the development of pre-implantation embryos remains to be determined. In addition, future work should be extended to human embryos to determine whether this mechanism is conserved between mice and humans. Wider implications of the findings The findings of this work indicated the relationship between CuONPs and epigenetic modification. The results will support a more thorough understanding into the biosafety of CuONPs, and offer fresh perspectives on the potential uses of nanomaterials in the field of reproductive medicine in the future. Trial registration number Not Applicable

Nonpronuclear- and monopronuclear-derived blastocysts do not impair subsequent perinatal and maternal outcomes.

The routine clinical practice is to prioritize the transfer of blastocysts derived from 2PN embryos if they are available. For women who only have blastocysts resulting from 0PN and 1PN embryos, whether to transfer these embryos or discard them has been an ongoing debate over the years. To investigate the perinatal and obstetric outcomes following the transfer of vitrified-warmed single blastocysts derived from 0PN and 1PN zygotes. Retrospective cohort study. University-affiliated IVF center. This study included singletons born to women who had undergone 0PN and 1PN vitrified-warmed single blastocyst transfers, compared to those resulting from 2PN vitrified-warmed single blastocyst transfers from 2012 to 2020. None. Perinatal and obstetric outcomes. A total of 7,284 women were included in the final analysis. Of these, 386, 316, and 6582 cycles resulted from 0PN-, 1PN-, and 2PN-derived blastocysts transfer, respectively. The rates of clinical pregnancy, miscarriage, and live birth were similar across the study cohorts in both unadjusted and adjusted analyses. When comparing the 0PN and 2PN groups, no differences were found in birth outcomes after adjusting for confounders. Similarly, maternal complications and mode of delivery were comparable between these two study cohorts. Birth parameters were also similar between the 1PN and 2PN blastocyst groups, except for more male births in the 1PN cohort. Furthermore, a comparison between the 1PN and 2PN groups did not reveal any significant differences in maternal outcomes. The current study showed that the transfer of 0PN and 1PN blastocysts did not compromise reproductive outcomes or increase maternal and perinatal complications. This information is valuable for clinicians to counsel couples effectively and guide them in making informed decisions.

Two types of cleavage, from zygote to three cells, result in different clinical outcomes and should be treated differently.

What is the utilization rate of embryos that exert inadequate zygote cleavage into three daughter cells? This study used a retrospective dataset from a single IVF Unit. A total of 3,060 embryos from 1,811 fresh IVF cycles were analyzed. The cleavage pattern, morphokinetics, and outcome were recorded. Only 2pn embryos, fertilized by ejaculated sperm, and cultured in a time-lapse system for at least 5 days were included. We generated three study groups according to the embryo's cleavage pattern: (I) Control, normal cleavage (n = 551); (II) fast cleavage, zygote to three cells within 5h (n = 1,587); and (III) instant direct tripolar cleavage (IDC) from zygote to three cells (n = 922). The rate of usable fast cleavage blastocysts was 108/1,587 (6.81%) and usable control blastocysts was 180/551 (32.67%). The time of PN fading and from fading to first cleavage differed significantly between the three groups. Although the pregnancy rate of control and fast cleavage blastocysts were comparable (40.35% and 42.55%, respectively), the amount of instant direct cleavage embryos that reached blastocyst stage was neglectable (only four embryos out of 922 analyzed IDC embryos) and unsuitable for statistical comparison of pregnancy rates. Our results indicate the need to culture instant direct cleavage embryos for 5 days, up to the blastocyst stage, and avoid transfer of embryos that are fated to arrest even when their morphological grade on day 3 is acceptable, whereas fast cleavage embryos could be transferred on day 3 when there is no alternative.

Comparison of the pregnancy outcomes of progestin-primed vs. antagonist ovarian stimulation in patients with poor ovarian response: a retrospective study

Objectives Progestin-primed ovarian stimulation (PPOS) is an efficient controlled ovarian stimulation (COS) method. The study explored the pregnancy outcomes between PPOS and antagonist ovarian stimulation protocol (GnRH-ant) in infertile patients with poor ovarian response (POR). Methods This retrospective study included patients with POR who underwent COS at the Reproductive Medical Center of Shanxi Maternal and Child Health Hospital from January 2021 to April 2022. The cycles were grouped as the GnRH-ant group and the PPOS group. The primary outcome was the clinical pregnancy rate; the secondary outcomes included the biochemical pregnancy abortion rate and live birth rate. Results Frozen embryo transfer was used in all cycles in this study. The cycles were divided into the GnRH-ant (n = 236 cycles) and PPOS (n = 273 cycles) groups. Age, BMI, type of infertility, infertility duration, FSH, LH, PRL, E2, T, P, and the number of cycles in the hospital were similar between the two groups (all p > 0.05). No statistically significant differences were observed in the clinical pregnancy rate (primary outcome, 32.71% vs. 43.90%, p = 0.082), total Gn dose, total Gn days, ART mode (IVF or ICSI), AFC, MII follicles, 2PN embryos, fertility, cycle cancelation rate, biochemical pregnancy rate, abortion rate, or live birth rate between the two groups (all p > 0.05). The PPOS group exhibited a higher rate of high-quality embryos than the GnRH-ant group (50.12% vs. 42.90%, p = 0.045). Conclusions The PPOS protocol was comparable to the GnRH-ant protocol regarding induction parameters and cycle cancelation, biochemical pregnancy, clinical pregnancy, and abortion rates but might be associated with a higher proportion of high-quality embryos.

The association between triglyceride glucose-body Mass Index and in vitro fertilization outcomes in women with polycystic ovary syndrome: a cohort study

BackgroundPolycystic Ovary Syndrome (PCOS) is a common reproductive disorder that frequently affects fertility. The TyG-BMI (Triglyceride glucose-body mass) index is a newly explored parameter that may be linked to reproductive results in individuals with PCOS. Nevertheless, its connection with outcomes in In Vitro Fertilization (IVF) procedures remains uncertain.MethodsThis study included a total of 966 females who underwent IVF treatments for PCOS. At the baseline, the participants were categorized into four groups according to the quartiles of TyG-BMI measured prior to oocyte retrieval. Subsequently, the study compared the differences in clinical and laboratory outcomes among these four groups.ResultsPatients in higher TyG-BMI quartiles exhibited a decreased number of retrieved oocytes, 2PN embryos, and available/high-quality embryos (P < 0.05 for Q1-Q4). Additionally, the multivariable regression analysis revealed that individuals in the top quartile of TyG-BMI had a lower count of accessible embryos (β = -0.224, P = 0.257) and a decreased number of high-quality embryos (β = -0.352, P = 0.028) in comparison to those in the lowest quartile. Nevertheless, there were no notable variances detected in the rates of pregnancy or live births among these quartiles. Furthermore, a linear correlation was noted between the TyG-BMI index and the quantity of accessible embryos (P-non-linear = 0.6, P-overall < 0.001), along with high-quality embryos (P-nonlinear = 0.026, P-overall = 0.006). In contrast, there was no notable linear correlation found between the TyG-BMI index and the available embryo rate (P-nonlinear = 0.60, P-overall = 0.8).ConclusionsThe results of this research emphasize the notable correlation between TyG-BMI and IVF results in females diagnosed with PCOS. The interplay of insulin resistance and disorders of lipid metabolism may indeed play a pivotal role in influencing the assisted reproductive outcomes of patients with PCOS. Considering these findings, TyG-BMI proves to be a valuable indicator for exploring this potential association.

The utility of human two plus one small pronucleated zygotes (2.1PN) based on clinical outcomes and the focused ploidy analysis

PurposeAre human embryos arising from two plus one small pronucleated zygotes, called 2.1 pronuclei (PN), clinically useful?MethodsIn a retrospective embryo cohort study and prospective experimental study, a total of 287 cycles in which at least one 2.1PN was identified in the fertilization check were included. Embryonic development and clinical outcome were compared for the 1395 2PN zygotes and 304 2.1PN zygotes that were siblings. All embryos were individually cultured in time-lapse systems. Twenty-five 2.1PN-derived blastocysts, donated for research, were used in focused single-nucleotide variant ploidy analysis to identify the distribution pattern of heterozygosity.ResultsThe average diameter of PN was 24.9 ± 2.4 µm for large PN and 10.2 ± 2.4 µm for small PN; 79.9% of small PN was derived from female pronuclei. Blastocyst formation rate and good-quality blastocyst rate were significantly lower with 2.1PN embryos than with 2PN embryos (40.0% vs. 57.7%, 21.4% vs. 33.5%, respectively). A total of 13 embryos derived from 2.1PN were transferred, and three healthy babies were born. In ploidy constitutions of trophectoderm (TE), 2.1PN-derived blastocyst TE was shown to be mostly diploid (95.8%, 23/24), and only one blastocyst showed triploid.ConclusionsIt was suggested that 2.1PN embryos have lower embryonic developmental potential than 2PN embryos, but most of the 2.1PN were diploid, indicating that they are likely to be clinically usable. It is recommended to perform embryo transfer following a combination of PGT-A and ploidy analysis.

Developmental potential of non- and mono-pronuclear zygotes and associated clinical outcomes in IVF cycles.

This study aims to evaluate the developmental potential of 0PN, 1PN, and 2PN zygotes in IVF cycles and compare their clinical outcomes. We conducted a retrospective cohort study involving IVF patients. Blastocyst formation rates were assessed with 0PN, 1PN, and 2PN zygotes. Subsequently, we collected clinical outcome data following the transfer of these zygotes. The overall blastulation rate was similar between 0PN (29.6%) and 2PN (32.1%) zygotes, but 1PN zygotes exhibited a significantly lower blastulation rate (17.0%) compared to both 0PN and 2PN zygotes. Similarly, the overall rate of good-quality blastulation was comparable between 0PN (15.3%) and 2PN (17.5%) zygotes, while 1PN zygotes showed a significantly lower rate (7.0%) compared to both 0PN and 2PN. Clinical pregnancy, ectopic pregnancy, implantation, and live birth rates were similar among single blastocyst frozen embryo transfers (FET) of 0PN, 1PN, and 2PN. Additionally, no significant differences were observed between single- and double-blastocyst FET of 0PN and 2PN. Our findings suggest that 0PN and 2PN zygotes have comparable developmental potential, while 1PN embryos exhibit lower developmental potential. Blastocyst FET outcomes appear similar among 0PN, 1PN, and 2PN zygotes.

Ovarian response determines the luteinizing hormone suppression threshold for patients following the gonadotrophin releasing hormone antagonist protocol: A retrospective cohort study

BackgroundOvarian reactivity to gonadotrophin stimulation varies, and individual adjustments to the timing and dose of gonadotrophin-releasing hormone (GnRH) antagonist administration are necessary to prevent excessive increases and decreases in luteinizing hormone (LH) levels in patients with different ovarian response following the GnRH antagonist (GnRH-A) protocol. The present study aims to investigate optimal LH suppression thresholds for patients with normal ovarian response (NOR), high ovarian response (HOR), and poor ovarian response (POR) following the GnRH-A protocol respectively. MethodsA total of 865 in vitro fertilization (IVF) cycles using a flexible or fixed GnRH-A protocol were included. Patients were categorized into the HOR, NOR, or POR group according to their anti-Müllerian hormone (AMH) levels. Then, patients in each group were stratified into one of four subgroups according to the quartile (Q1-Q4) of the basal LH level to LH on triggering day ratio (bLH/hLH). The primary outcomes were the clinical pregnancy and live birth rates, and the secondary outcomes were the number of oocytes retrieved, MII oocytes, two pronucleus (2PN) embryos, and good-quality embryos. ResultsThere were 526 patients with NOR, 180 with HOR, and 159 with POR. Basal LH level, LH on triggering day and bLH/hLH were identified as independent predictors of clinical pregnancy rate and live birth rate by logistics regression analysis. Compared to those with NOR, patients with POR had the lowest embryo implantation rate (22.6% vs. 32.8%, P < 0.05), clinical pregnancy rate (32.3% vs. 47.3%, P < 0.05) and live birth rate (22.6 vs. 37.8%, P < 0.05) of fresh embryo transfer (ET). The embryo implantation, clinical pregnancy and live birth rates of frozen embryo transfer (FET) were not significantly different among the three groups. In the subgroup analysis, patients with HOR had the highest embryo implantation rate (51.6%, P < 0.05), clinical pregnancy rate (68.4%, P < 0.05) and live birth rate (52.6%, P < 0.05) of ET in Q3, with a bLH/hLH ratio of 2.40–3.69. In the NOR group, the embryo implantation rate (41.9%, P < 0.05), clinical pregnancy rate (61.5%, P < 0.05) and live birth rate (50.8%, P < 0.05) of ET and live birth rate (53.1%, P < 0.05) of FET were highest in Q2, with a bLH/hLH ratio of 1.29–2.05. Patients with POR had the highest clinical pregnancy rate (57.1%, P < 0.05) and live birth rate (42.9%, P < 0.05) of ET in Q2, with a bLH/hLH ratio of 0.86–1.35. ConclusionsIn the present study, the bLH/hLH ratio represented the LH suppression threshold. The subgroup analysis of HOR, NOR and POR showed that, the LH suppression threshold varies according to ovarian response. We recommend LH suppression thresholds of 2.40–3.69 for HOR, 1.29–2.05 for NOR, and 0.86–1.35 for POR to obtain the highest clinical pregnancy rate and live birth rate. This study provides comprehensive and precise references for clinicians to monitor LH levels individually during controlled ovarian stimulation (COS) according to the patient’s ovarian response following the GnRH-A protocol.

#290 : Does Extending the Time Interval Between hCG Trigger and Oocyte Retrieval from 36 to 37 Hours Affect the Rate of Euploid Blastocysts?

Background and Aims: Data are lacking regarding the optimal time interval between human chorionic gonadotropin (hCG) administration and ovum pick-up (hCG-OPU interval), and its impact on blastocyst euploidy. Our aim was to compare the blastocyst euploidy rate between IVF cycles with hCG-OPU interval of 36 and 37 h. Method: In this historic cohort study, we reviewed all hCG-triggered, PGT-A, IVF cycles performed in a single clinic, between 2018 and 2022. Commencing in September 2021, clinicians gradually changed the hCG-OPU interval from 37 to 36 h. We compared the outcomes of cycles with hCG-OPU interval of 36 h (35.5-36.5) to 37 h (36.6-37.5). The primary outcome was the number of euploid embryos. Cycles with oocyte donation, and cycles utilized GnRH-agonist triggers or dual-triggers were excluded. Results: The euploidy rates were similar between the 36-h group (n=2,584) and 37 h group (n=5,575; 39.7% vs. 38.8%, respectively, p=0.42). Compared to the 36-h group, patients in the 37-h group were characterized by higher numbers of total oocytes collected (15.9±8.9 vs. 17.3±9.8, respectively, p&lt;0.001), mature (MII) oocytes (8.3±8.2 vs. 9.6±9.6, respectively, p&lt;0.001) and 2PN embryos (9.8±5.5 vs. 10.3±6.4, respectively, p&lt;0.001). On multivariate logistic regression analysis, the hCG-OPU interval was not associated with euploidy (aOR 0.91, 95% CI 0.82-1.01), after controlling for female and male ages, female BMI, and number of oocytes collected. Conclusion: hCG-OPU intervals of 36 and 37 h resulted in similar blastocyst euploidy rates in IVF cycles. This finding has the potential to aid the decision-making processes when managing IVF procedures. The 37-h group was characterized by a lower female age and higher doses of gonadotropins and consequentially more eggs collected, mature eggs and 2PN embryos compared to the patients of the 36 h group. Nonetheless, the two groups had comparable rates of euploid embryos reinforcing our primary finding. Data are presented as mean ± standard deviation or n (%); hCG- Human chorionic gonadotropin; OPU- ovum pickup; BMI- BMI kg/m2, Gonadotropins- in IU; ICSI- Intra cytoplasmic sperm injection. Data are presented as mean ± standard deviation or n (%); hCG- Human chorionic gonadotropin; OPU- ovum pickup; 2PN- 2 Pronuclei.