Poor Responders Research Articles

O-152 Pre-implantation genetic testing for aneuploidies (PGT-A) improves reproductive outcomes in advanced maternal age patients undergoing IVF/ICSI: a multicentre retrospective cohort study with propensity score matching

Abstract Study question In patients > 37 years undergoing IVF/ICSI, does PGT-A improve live birth rates (LBR) and cumulative live birth rates (CLBR)? Summary answer In advanced maternal age women with ≥1 embryo to transfer, PGT-A improves the live birth and cumulative live birth rates. What is known already The age-related rate of aneuploidy remains a major cause of IVF failure. Therefore, PGT-A has been proposed as a method to select embryos with the highest implantation potential. Previous studies have shown that women younger than 37 years old do not benefit from PGT-A given the comparable outcomes in terms of implantation, clinical pregnancy, and live-birth rates. Moreover, PGT-A may also be inherently ineffective given the risk of mitotic mosaicism, sampling errors and misinterpretation of results. However, we are currently lacking solid scientific evidence to support whether this approach benefits advanced maternal age women. Study design, size, duration A multicenter retrospective cohort study was conducted including 9328 patients >37y undergoing their first IVF/ICSI cycle with an oocyte retrieval performed between 1/01/2013-31/07/2021 in a multinational private fertility clinic. The study group (n = 4664) included patients who performed PGT-A. The control group included patients without PGT-A (n = 4664) and was selected by propensity score matching adjusted for age at oocyte retrieval, number of oocytes retrieved and year of oocyte retrieval. Participants/materials, setting, methods The primary outcome was CLBR (delivery of at least one live birth per started cycle, including the fresh and subsequent frozen embryo transfer cycles). The secondary outcomes were LBR and time to pregnancy. The analysis was conducted including all patients with an initiated cycle of ovarian stimulation and also per embryo transfer. Comparisons are presented as adjusted odd-ratios (adjOR) and 95% confidence intervals (95%CI) following multivariable logistic regression (LBR) or cox regression (CLBR) analysis. Main results and the role of chance Patients in the PGT-A group had more oocytes retrieved (11.03±6.82 vs 9.24±6.15, p < 0.001), and a higher number of available blastocysts (2.82±2.21 vs 1.22±2.00, p < 0.001). In the PGT-A group, 13.153 embryos were analysed, with an euploidy rate of 29.30% (n = 3854). In total, 49.83% (n = 2324) patients did not undergo embryo transfer due to unavailable euploid embryos. Considering all patients that initiated ovarian stimulation, the PGT-A group presented a higher unadjusted CLBR per started cycle (27.38% vs 21.81%, p < 0.001). Considering only patients who underwent embryo transfer, a total of 5934 embryo transfers were analysed (n = 3166 in the control group and n = 2768 in the PGT-A group). Following multivariable logistic regression analysis, LBR and CLBR were significantly higher in the PGT-A group (respectively, adjOR 1.56 [95% CI 1.38-1.77], adjOR 1.53 [95% CI 1.39-1.68]). Following the transfer of 5 embryos, the CLBR was approximately 100% in the PGT-A group and 74.51% in the control group. Survival analysis was also perfomed to assess the impact of PGT-A on time to pregnancy. Despite the fact that from 6 months onwards the CLBR was higher in the PGT-A group, the median time to pregnancy was higher in the PGT-A group (3.27 (95%CI 3.16-3.40) vs 2.74 months (95%CI 2.57-3.03). Limitations, reasons for caution This study is limited by its retrospective design and low number of women with more than 3 embryos transferred. Also, the fact that only the first IVF/ICSI cycle was analysed provides a proper patient counselling in this specific context but does not provide data on repeated cycle outcomes. Wider implications of the findings Our findings suggest that, in women older than 37 years with at least one available embryo to biopsy, performing PGT-A may improve the reproductive outcomes in terms of LBR and CLBR, providing a useful clinical tool for embryo selection. Trial registration number not applicable

P-660 Finding the optimal starting dose of gonadotropins for an ovarian stimulation treatment through Machine Learning

Abstract Study question Can machine learning algorithms provide an individualized starting dose of gonadotropins to maximize the number of oocytes retrieved in patients undergoing ovarian stimulation ? Summary answer Methods of Policy Learning based on Causal Inference and Machine Learning optimize starting doses of gonadotropins with a substantial gain of oocytes under appropriate treatment. What is known already Despite attempts toward standardization, there has been no consensus about establishing the optimal starting dose of gonadotropins to be used in ovarian stimulation. In the real world, medical practice differs considerably across countries and even among fertility clinics nationally. The machine learning community has proposed a variety of models for doing this, but with limited comparisons, causal inference can provide the statistical tools to enable the best model to be chosen and allow its explicability. Study design, size, duration In a retrospective single-center study, we reviewed the data of 11,436 cycles of ovarian stimulation for IVF between 2012 and 2023. In order to estimate the causal effect of the starting dose of gonadotropins on the number of oocytes retrieved, we selected a relevant subset of confounding covariates – including age, Antral Follicle Count (AFC), Anti-Müllerian Hormone (AMH) and oestradiol (E2) rates. Participants/materials, setting, methods We used five different Machine Learning models : Linear Regression, Regression Forest, Super Learner (SL), Multi-Arm Causal Forest (MACF) and a model based on the Targeted Maximum Likelihood Estimation (TMLE). We employed these models for Policy Learning through an Outcome Regression Modeling approach. We compared the gain of oocytes obtained through the optimal policy of our different models and analyzed the variables which played a crucial role in determining the optimal dose. Main results and the role of chance We use two approaches to compare our models, the first one gives the expected average gain of oocytes under the optimal policy : in this case, the Linear Regression is the best with an average gain of 0.90 oocytes, followed by the MACF (0.80), the SL (0.58), the TMLE (0.44) and the Regression Forest (0.18). Considering the lack of heterogeneity of our database we use a second approach, an Augmented Inverse Propensity Score based value, to compare with more robustness the performance of the optimal policy of each model. In this case the MACF (an explainable model specifically designed for causal inference) is the best with a gain of 0.50 oocytes, followed by the SL (0.42), the Linear Regression (0.37), the TMLE (0.23) and the Regression Forest (0.18). In general, our models recommend lower doses, for instance 20% of the patients are recommended by the MACF to reduce their initial doses of gonadotropins by on average 100 IU. The most significant covariates in the models are the AFC, the BMI, and the rate of AMH, with p-values < 0.001 in the Linear Regression that has a R-squared of 0.418. Limitations, reasons for caution Full IVF history was not included in patients who had previous IVF attempts, but only data from the last previous attempt was considered. Also, the study is monocentric and more heterogeneity will be present considering other centers. Wider implications of the findings This study needs to be completed by data from different centers in France and around the world to bring diversity to the patients’ data and to the treatment prescriptions in order to improve external validity. Algorithm recommendations and their adherence need to be tested prospectively. Trial registration number not applicable

O-043 Con

Abstract Dual and/or double trigger improve IVF success - CON The improvement of in vitro fertilization (IVF) outcomes remains a pivotal area of reproductive medicine research, with the dual trigger approach emerging as a significant innovation. This con abstract explores the scientific basis, methodology, and outcomes associated with the dual trigger strategy, juxtaposed with conventional triggering methods in IVF protocols. The dual trigger, incorporating both Gonadotropin-Releasing Hormone Agonist (GnRHa) and Human Chorionic Gonadotropin (hCG), has been posited to improve oocyte maturation, retrieval-, and live birth rates. By scrutinizing recent studies, clinical trials, and meta-analyses, this debate aims to delineate the efficacy, safety, and application scope of this approach. Initial investigations into the dual trigger method have highlighted its potential to ameliorate oocyte quality and maturity, which are crucial determinants of IVF success. The mechanism underlying this improvement involves the simultaneous activation of LH (Luteinizing Hormone) and FSH (Follicle Stimulating Hormone) receptors, enhancing follicular response and oocyte developmental competence. Studies have demonstrated an increase in the number of mature oocytes retrieved, attributed to the more synchronized and comprehensive follicular stimulation afforded by the dual trigger. This augmentation in oocyte quality and quantity directly correlates with enhanced embryo development profiles, and higher implantation and clinical pregnancy rates. Furthermore, the dual trigger method has shown promise in reducing the incidence of Ovarian Hyperstimulation Syndrome (OHSS), a severe complication of IVF treatments. By leveraging the luteolytic effects of GnRHa, this strategy minimizes the risk associated with exogenous hCG administration, thus offering a safer alternative for patients predisposed to OHSS. The application of the dual trigger in specific patient cohorts, such as those with PCOS or poor ovarian responders, has been underlined, indicating its potential for personalized reproductive medicine. However, the implementation of the dual trigger strategy is not without challenges. Variability in patient response necessitates a highly individualized approach, with precise dosing and timing adjustments to optimize outcomes. The existing literature presents a heterogeneity in study designs, populations, and outcome measures, which complicates the direct comparison of dual trigger efficacy against traditional methods. Furthermore, the long-term safety and potential impacts on offspring warrant further investigation, given the recent adoption of this approach. In conclusion, the dual trigger strategy may offer significant benefits in enhancing IVF outcomes. Its potential to improve oocyte maturity and quality could increase the number of retrievable oocytes and reduce the incidence of OHSS. However, it is important to acknowledge that, while the GnRH agonist trigger combined with a freeze-all strategy eliminates the risk of OHSS in women with PCOS, the dual trigger approach followed by fresh embryo transfer does not. Further research is imperative to refine its application, understand its mechanisms fully, and establish comprehensive guidelines for its use. The promise of the dual trigger approach underscores the importance of continuous innovation and evidence-based practices in enhancing the efficacy and safety of IVF treatments.

P-214 Direct unequal cleavage-1 (DUC1) in IVF/ICSI cycles: relationship with patient characteristics and insemination method

Abstract Study question Does the incidence of DUC1 in IVF/ICSI cycles vary with the maternal profile and insemination method? Summary answer The incidence of DUC1 cycles is higher in patients with a more favourable prognosis. DUC1 embryos are more frequent in ICSI than in IVF cycles. What is known already The emergence of Time-Lapse Microscopy (TLM) has enabled a dynamic and thorough evaluation of in vitro embryo development, unveiling the occurrence of morphological phenomena unobserved with static observation, such as direct unequal cleavage (DUC), which is associated with a drastically reduced competence to implant. The incidence of DUC-1 (DUC immediately after syngamy) has been reported to vary from 8.3% to 26%, but the reasons underlying its occurrence and variability are unknown. There is evidence that the maternal profile and insemination method can impact embryo developmental competence, but whether they impact the incidence of DUC is also unknown. Study design, size, duration The study includes 2920 first IVF/ICSI cycles (2018 to 2022) providing 12492 embryos. Cycles presenting male infertility were excluded from the analysis. The percentages of DUC1 embryos in relation to total embryos and of cycles providing at least one DUC1 embryo in relation to total cycles were compared between AMA (advanced maternal age; ≥35) and pre-AMA (<35) cycles. Patient/cycle characteristics were compared between cycles with and without DUC1 occurrence in AMA and pre-AMA cycles, separately. Participants/materials, setting, methods Ovarian stimulation was induced with rFSH or with a combination of FSH and LH using classic antagonist or short agonist protocols. Oocytes were inseminated with either IVF or ICSI standard methodology. Embryo culture was performed in an integrated embryo culture Time-lapse System (EmbryoScope; Vitrolife). Differences between percentages were assessed by the Fisher’s exact test, while differences between continuous variables were assessed with the Wilcoxon sum rank test. Main results and the role of chance The percentage of DUC1 embryos in relation to total embryos did not vary between pre-AMA (5.4%) and AMA (5.2%; p > 0.05) cycles. Alternatively, the incidence of cycles providing at least one DUC1 embryo was higher in pre-AMA (21.7%) as compared with AMA patients (16.0%; p < 0.0001). In both pre-AMA and AMA cycles, DUC1 occurrence was associated with higher oocyte yield (13.5±7.7 vs. 10.6±6.7 and 11.0±6.3 vs. 7.5±5.5, respectively; p < 0.0001), higher AMH serum levels (4.4±4.7 vs. 3.4±3.2 and 3.0±3.6 vs. 2.1±2.1ng/mL, respectively; p < 0.004) and lower basal FSH serum levels (7.0±2.1 vs. 7.6±2.9 and 7.8±3.3 vs. 8.5±3.4mU/mL, respectively; p < 0.0001). Overall, the percentage of DUC1 embryos was higher in ICSI (5.6%) as compared to IVF (4.4%, p < 0.01) cycles. However, when the data was stratified by maternal age, DUC1 incidence was significantly higher in ICSI vs. IVF in AMA (5.6 vs 4.0%; p = 0.002) but not in pre-AMA (5.7 vs 5.0%; p = 0.19). All 21 DUC1 embryos transferred during the study failed to implant. Limitations, reasons for caution Our study is limited by its retrospective nature. The present conclusions must be confirmed in other patient populations with different race/genetics and habits. Wider implications of the findings The occurrence of cycles providing DUC1 embryos is paradoxically associated with a more favourable patient prognosis, and the percentage of DUC1 embryos is higher in ICSI as compared to IVF cycles in AMA patients. Our findings represent new valuable clues for the clarification of DUC1 underlying causes. Trial registration number NA

P-361 Preserving fertility prior to hematopoietic stem cell transplant in post-pubertal women with sickle cell anaemia

Abstract Study question Can fertility preservation (FP) in women with sickle cell anemia (SCA) be linked to an increased risk of hematopoietic complications? Summary answer Only one participant on sixteen in our series had to discontinue the ovarian stimulation due to a complication related to a painful vaso-occlusive crisis (VOC). What is known already SCA is one of the most common severe monogenic diseases worldwide. It is a multisystemic disorder characterized by anaemia, increased haemolysis, and VOC. Despite advances in management, patients remain at a high risk of significant morbidity, especially increased thromboembolic events and early death. With the introduction of hematopoietic stem cell transplantation(HSCT) for non-malignant conditions, there is now a curative treatment for this debilitating condition. The myeloablative regimens for HSCT may impact ovarian reserve; therefore consideration of FP could be recommended. There is limited data on FP in this context and the risk of hematopoietic complications such as VOC is unclear. Study design, size, duration Cohort of women with SCA consulting at our center for FP before a HSCT project between 2016 and 2023. FP modalities were oocytes vitrification after ovarian stimulation and ovarian tissue cryopreservation (partial unilateral ovariectomy under laparoscopy). A protocol for the prevention of the risk of VOC, including hydration, oxygen therapy, and warming ± transfusion exchanges and for thromboembolic events was initiated before and during FP treatment, tailored on a case-by-case basis with the referring haematologist. Participants/materials, setting, methods The data related to hematopoietic complications (including VOC and thromboembolic event) [ps1] during FP were collected. Additionally, data on the follow-up of SCA, including received and planned treatments post-FP, were collected. This encompassed information on the completed FP treatments, preventive measures for SCA complications, and the outcomes of FP. Descriptive analysis was conducted. Main results and the role of chance During the study period, sixteen women affected with SCA aged 15–37 years have consulted for FP in our center. The mean age and BMI were 28.43±6.66 years and 21.97 ±3.46 respectively. The mean AMH level and antral follicle count were 1.77±1.70 and 15.83 ±7.12 respectively. Twelve patients underwent oocytes vitrification after mulfifollicular ovarian stimulation (OS), two had ovarian tissue cryopreservation, and 1 underwent both technics. One patient, initially planning for OS, cancelled after counselling. Among the 13 women that received an OS, 18 cycles were performed in total. The mean number of OS cycles per patient was 1.38±0.73. Protocols were antagonist (n = 16) or short agonist protocols (n = 2). The mean duration of gonadotropin treatment was 9.91±1.84 days, and the mean total gonadotropin dose was 3187.5±711.8 IU. Five OS were cancelled before oocyte retrieval because of an insufficient ovarian response. The mean number of oocytes retrieved was 8.83±5.61 per cycle. The mean number of cryopreserved oocytes was 12.00±5.66. One patient had to discontinue the OS due to a complication related to a painful VOC at 3 days of stimulation. As recommended, the hydroxycarbamide treatment was temporarily suspended to perform the FP. For patients who underwent unilateral partial ovariectomy, no complications were reported. Limitations, reasons for caution The main limitation is that this study is a small, retrospective case series; however, this represents the largest series to date. Wider implications of the findings Although limited, current data suggest that FP with specific conditioning does not pose a significant risk of complications in patients with SCA who are to undergo gonadotoxic treatment for HSCT. Trial registration number NA

O-320 Does applying an ‘elective freeze-all’ policy work in practice? A matched cohort study of over 9,000 embryo transfers

Abstract Study question Does application of a Freeze All Embryo (FAE) policy achieve superior live birth rates in practice compared to fresh IVF transfer cycles? Summary answer FAE FETs achieved significantly higher LBRs than fresh for both the first ET per cycle and cumulatively per cycle. What is known already The efficacy of vitrification methods has led to segmentation between the ovarian stimulation and embryo transfer cycle becoming increasingly applied. Randomised controlled trials have shown that for high responders, especially those at risk of ovarian hyperstimulation syndrome, the FAE approach is likely to be favourable. However, whether a routine freeze all approach applied in routine clinical practice improves outcomes in a broader group of patients remains unclear. Study design, size, duration This is a retrospective analysis of 7,647 autologous fresh oocyte retrievals and 9,609 subsequent ETs, performed between 2016-2022. The primary study aim was to compare (cumulative) live birth rates between fresh and frozen thawed embryo transfers after FAE IVF cycles. The groups consisted of 3,707 fresh IVF transfers plus 1,533 subsequent FETs derived from those cycles, versus 3940 FAE cycles with 3969 subsequent FETs. Participants/materials, setting, methods 5,808 patients underwent fresh oocyte retrievals (2016-2022) at a single UK-based centre. In total, 4,997 of these patients underwent 9,609 ETs; either fresh or frozen. For analysis, FAE cycles and fresh IVF cycles underwent 1:1 full propensity score matching for age and number of eggs collected, using probit regression of treatments on covariates. Logistic regression analyses were fit including full matching weights in the estimation to compare LBR superiority between groups. Main results and the role of chance Patients undergoing fresh transfers were significantly older and yielded significantly fewer oocytes per retrieval (37 and 36, P < 0.001; 7 ± SE 0.07 and 12 ± SE 0.1, P < 0.001, respectively). After full 1:1 matching for age and oocytes collected, the means for both groups were 36 and 15, respectively. Standardised mean differences after matching was <0.2. The first FET from FAE cycles achieved significantly superior LBRs and was a significant predictor of LB compared to fresh ETs when adjusted for covariates (37% and 26%, respectively, aOR 1.3; 95% CI 1.2-1.5, P < 0.001). Cumulative LBs achieved per cycle were also significantly higher for FAE cycles (56% and 37%, respectively). When stratifying by age, first ET LBRs between groups were comparable for <35s (FAE 42%, fresh 40%). However, with increasing age, FAE first FETs achieved higher live births than fresh transfers (35-37, 36% and 33%; 38-39, 34% and 23%; 40-42, 27% and 14%; 43-45, 15% and 5%, respectively). Limitations, reasons for caution This is a retrospective analysis and, although cohorts underwent full 1:1 matching, inherent bias may be present within the data and must be considered when drawing conclusions. Wider implications of the findings These findings suggest that in clinical practice, FETs after a FAE cycle may achieve superior LBRs compared to fresh ETs, particularly in older patients and for higher responders. Overall, FAE cycles were observed to result in higher cumulative LBRs per cycle than cycles that begin with a fresh transfer. Trial registration number Not applicable

P-046 Ejaculatory abstinence: is there any association with embryo developmental competence? A Retrospective Study in time-lapse incubators

Abstract Study question Is ejaculatory abstinence (EA) associated with fertilization and blastocyst development in ICSI cycles with embryo culture in time-lapse incubators? Summary answer There is no association between length of EA and fertilization, blastocyst development or morphology. What is known already Semen analysis is pivotal in medically assisted reproduction (MAR), serving as a significant indicator of male partners’ health. The period of EA is a relevant factor that can affect sperm quality. Numerous studies described EA association with clinical outcomes, while its impact on embryological results remains inconclusive. Recent meta-analyses, despite a conflicting literature, highlighted positive effects of shorter abstinence periods. A recent study suggested that prolonged abstinence might reduce fertilization rate in ICSI cycles without time-lapse imaging, thereby reducing usable zygotes’ rate Study design, size, duration Retrospective study including all oocytes (N = 7164) from 1148 ICSI cycles (N = 902 couples) cultured in time-lapse incubators at a single IVF center between January 2020 and December 2022. Only non-donor fresh gametes were included (Mean Maternal age: 38.5±4 years; Paternal Age: 41±5.6 years). The primary embryological outcomes were fertilization rate and type, and blastocyst development per inseminated oocyte and per 2PN-zygote. Secondary outcomes were euploidy, day of blastocyst development and Gardner’s morphology. Participants/materials, setting, methods Semen analysis was conducted according to WHO. All oocytes were cultured up to day7 in EmbryoScope or GERI incubators with continuous media and refresh in day5 (if needed). If requested, PGT-A was performed to assess full-chromosome uniform aneuploidies. Univariate and multivariate logistic regressions were conducted. Possible confounders were assessed among ovarian stimulation, maternal, paternal, sperm, and IVF cycles characteristics. Associations were confirmed with Generalized estimating equations (GEE) to account for repeated measurements among oocytes’ cohort. Main results and the role of chance Logistic regressions and GEE were conducted to assess associations between possible confounders and blastocyst development per inseminated metaphase-II oocyte. Maternal age, sperm concentration, and motility A+B were associated. The same confounders were reported on blastocyst development among 2PN-zygotes. The days of EA (1-8 days) did not show any association with fertilization (p = 0.198) or blastocyst development per metaphase-II oocyte (p = 0.495). No association was reported with abnormal fertilization, neither combining all abnormalities in a single group, nor clustering them as 1PN, 3PN, 3.1PN, and multi-PN. An increasing trend was reported in blastocyst development among 2PN-zygotes according to the length of EA (1-day: 17/37,45.9%; 2-days: 190/424,44.8%; 3-days: 1405/2574,54.6%; 4-day: 746/1410,52.9%; 5-days: 450/827,54.4%; 6-days: 70/133,52.6%; 7-days: 46/101,45.5%; 8-days: 85/162,52.5%), but this was not significant in a multivariate logistic regression (p = 0.887). Length of EA showed no association with euploidy (p = 0.424), nor with day of development (p = 0.966) and Gardner’s inner cell mass (p = 0.204) or trophectoderm (p = 0.428) morphology. Limitations, reasons for caution This study is inherently limited by its retrospective design. The limited number of cycles included was balanced using time-lapse incubators to improve the accuracy of fertilization check and benefit from an undisturbed embryo culture environment. Artificial Intelligence will be implemented to automate developmental timings’ annotation and objectify embryo quality assessment. Wider implications of the findings The length of EA seems not associated with embryological outcomes, adding to the controversy on this topic. Here, we included only ICSI cycles with blastocyst culture conducted in time-lapse to enhance the quality of the evidence. Larger datasets and diverse settings are now required, especially enriched with poor prognosis patients. Trial registration number not applicable

O-299 Exposure of antral follicles to progestins during stimulation does not cause molecular perturbations in gonadotropin-responsiveness and steroidogenic function of granulosa cells in progestin-primed IVF cycles

Abstract Study question Does progestin exposure cause any molecular perturbations in the steroidogenic features and gonadotropin responsiveness of the granulosa cells in progestin-primed ovarian stimulation (PPOS) cycles? Summary answer No. PPOS cycles are identical to antagonist cycles for gonadotropin receptor expression, response to gonadotropins, steroidogenic function at molecular level in normal responding IVF patients. What is known already PPOS is commonly used in IVF cycles as an alternative to antagonist cycles. Although accumulating evidence from clinical studies did not indicate any particular differences between these two types of stimulation protocol for IVF cycle characteristics, it is still unknown if exposure of antral follicle cohorts to synthetic progesterone derivatives during ovarian stimulation causes any subtle molecular aberrations in PPOS cycles in terms of steroidogenesis and gonadotropin responsiveness. To address this issue, detailed molecular analyses were conducted in the luteinized mural granulosa cells (GCs) obtained from the normal responding patients undergoing PPOS vs. antagonist IVF cycles. Study design, size, duration A translational research study in IVF patients. Participants/materials, setting, methods 55 normal responding IVF patients underwent ovarian stimulation either with PPOS using medroxy progesterone acetate (5mg twice daily) or, with GnRH antagonist cetrorelix acetate were included in the study. Recombinant forms of FSH and hCG were used for ovarian stimulation and ovulation trigger, respectively. Luteinized mural granulosa cells obtained during oocyte retrieval procedure were used for the experiments. Cell culture, quantitative real-time PCR, immunoblotting, confocal time-lapse live cell imaging and hormone assays were used. Main results and the role of chance Demographic and IVF characteristics of the patients undergoing ovarian stimulation with PPOS vs. GnRH antagonist were similar including ovarian-response, mature oocyte yield and fertilization rates. Molecular analyses revealed that the expression of the enzymes involved in sex-steroid synthesis (StAR, aromatase, 3B-HSD, 17B-HSD) and uptake/storage/utilization of cholesterol (LDL receptor, Hormone-sensitive lipase, hydroxy-methyl glutaryl Co-enzyme-A reductase and Sterol O-acyltransferase1) in the GCs of the PPOS cycles were comparable to the antagonist IVF cycles. Both cycles were also similar for the expression of FSH and LH receptors at transcriptional and translational level. Basal and hCG-induced increases in 3B-HSD expression and P4 production, and basal and FSH-induced increases in aromatase expression and E2 output of the GCs of the PPOS patients did not show any meaningful differences from the antagonist cycles. Similarly, basal and hCG-induced up-regulation in the LDL receptor expression and cholesterol uptake rate did not differ between the groups. Confocal imaging also revealed similar patterns of expression for the steroidogenic enzymes and their co-localization with mitochondria. Lastly, the expression of the other genes regulating cumulus expansion, ovulation and luteal function (Relaxin, ADAMTS-1 and EGF-like growth factor amphiregulin (AREG)) in the GCs of the PPOS cycles were comparable to the antagonist cycles. Limitations, reasons for caution Caution should be exercised when interpreting our data, which was produced in normal responders. It is unclear if the molecular parameters assessed here vary according to infertility etiologies, ovarian response type, mode of trigger and any other underlying ovarian pathology or systemic diseases that are concomitantly present. Wider implications of the findings This study provides reassuring molecular evidence that exposure of antral cohorts to progestins follicular growth phase does not appear to have any detrimental effect on their steroidogenic, ovulatory and luteal functions, suggesting that PPOS IVF cycles are not different from traditional antagonist cycles. Trial registration number not applicable

Intra-Ovarian Platelet-Rich Plasma (PRP) Injection in Management of POSEIDON IV Poor Responders before ICSI: Pilot Study

Abstract Background Poseidon IV poor responders are 35 years old or older women with antral follicle count < 5 and anti-Mullerian hormone < 1.2 ng/ml with cumulative live birth rate (CLBR) of 22.34% - 34.46% following ICSI. Aim of the Work To assess the effectiveness of intra-ovarian platelet-rich plasma (PRP) injection in POSEIDON IV poor responders before ICSI. Patients and Methods This study was conducted on women complaining from infertility at assisted reproductive techniques unit at Ain Shams University Maternity Hospital at the period from March 2021 till January 2022. We got a 55 cases matching the inclusion and exclusion criteria among them 25 cases accepted to participate as the study group (PRP group) and the others 30 cases refused to the participate PRP group and they were enrolled as a control group. Results Endometrium thickness at day of HCG trigger was statistically significantly higher among PRP group than among control group. Ovulation statistically was non-significantly more frequent among PRP group than among control group. Fertilization statistically was non- significantly more frequent among PRP group than among control group. biochemical pregnancy, clinical pregnancy, ongoing pregnancy statistically were non-significantly more frequent among PRP group than among control group. Conclusion According to the finding in this study intra-ovarian platelet-rich plasma (PRP) injection in POSEIDON IV poor responders before ICSI had a non-significant role regarding the laboratory variables and pregnancy outcomes. Hence, further studies are required.

P-122 The impact of severe male factor on morphokinetic embryo development in low-prognosis patients according to the POSEIDON criteria: an analysis of 10366 injected oocytes

Abstract Study question Does severe male factor infertility (SMF) impact embryo morphokinetic behavior in low-prognosis women as stratified by the Patient-Oriented Strategies Encompassing IndividualizeD Oocyte Number (POSEIDON) criteria? Summary answer Embryos from SMF patients showed lower KIDScore ranking than those from non-SMF (nSMF) patients, which may justify the reduced clinical outcomes contrasted to Control group. What is known already It has been reported that 37.1% of poor responder patients (POR) have infertile male partners. While the maternal influence has been well-investigated, the role of seminal quality on reproductive outcomes in POR remains questionable. Embryo monitoring with timelapse imaging (TLI) may be a valuable approach to evaluate whether sperm quality relates to association between POSEIDON classification and the competences of developing embryos. The aim of this study was to investigate whether SMF impacts embryo quality and morphokinetic behavior in the four groups of low-prognosis women as stratified by the POSEIDON criteria. Study design, size, duration This historical cohort-study was performed in a private university–affiliated IVF center, between Mar/2019 and Apr/2022. Kinetic data were analyzed in 10366 embryos cultured in a TLI incubator until day five, derived from 2272 patients undergoing ICSI. Patients were split into eight groups according to the POSEIDON criteria and the presence or absence of SMF (<5 × 106 sperms/mL). Embryo morphokinetics were compared among the groups (post hoc achieved power > 90%). Participants/materials, setting, methods Injected oocytes were cultured in the EmbryoScope+ incubator, which recorded the following kinetic markers: timing to pronuclei appearance and fading (tPNa and tPNf), two (t2), three (t3), four (t4), five (t5), six (t6), seven (t7), and eight cells (t8), morulae (tM), start of blastulation (tSB) and blastulation (tB). Durations of second and third cell cycles (cc2 and cc3) and timing to complete synchronous divisions s1, s2, and s3 were calculated. The KIDScore ranking was recorded. Main results and the role of chance POSEIDON group 1 embryos showed significantly slower tPNa, tPNf, t2, t3, t4, t6, and t7 compared to those from Control group. POSEIDON group 2 embryos showed significantly slower tPNa, t4, t6, t7, t8, and tM compared to those from Control group. Embryos in POSEIDON 2 SMF subgroup took longer than those in POSEIDON 2 nSMF subgroup, and those in both Control subgroups, to achieve tPNf, t2, t3, t5, tSB. POSEIDON group 3 embryos showed significantly slower t8, and cc2 compared to those from Control group. POSEIDON group 4 embryos showed significantly slower tPNf, t2, t3, t4, t5, t6, t7, t8, s2, and s3 compared to those from Control group. For POSEIDON groups 1, 2 and 4, and Control group, the KIDScore ranking was significantly different between SMF and nSFM subgroups. KIDScore ranking was significantly different across all the subgroups in POSEIDON 3. Irrespective of sperm quality, implantation and miscarriage rates were significantly improved in Control subgroups compared to POSEIDON 2 subgroups, there were trends toward improved clinical outcomes in Control subgroups compared to POSEIDON 3 subgroups, and pregnancy, implantation and miscarriage rates were significantly improved in Control subgroups compared to POSEIDON 4 subgroups. Limitations, reasons for caution The use of historical cohort groups is a drawback. Despite the eligibility criteria for inclusion in the analysis, potential differences in the baseline characteristics cannot be ruled out. Wider implications of the findings The results presented contribute to the understating of the relationship between sperm quality and embryo morphokinetic behavior in POSEIDON patients. Embryo quality, as assessed by TLI-imaging, and clinical outcomes were significantly lower in POSEIDON SMF patients, suggesting that both oocyte (quantity and quality) and sperm are determinant of embryo development. Trial registration number N/A

P-520 Analyses of mosaic embryos reveal critical regions on human chromosome 11 that involve embryo implantation

Abstract Study question Why some mosaic embryos can be implanted, whereas others cannot? What are the secrets hidden in the human genome that control embryo implantation? Summary answer By data-mining genomic information from PGT-A results of 109 mosaic embryos, we have defined the critical regions in chr11 that play essential roles in implantation. What is known already Embryo implantation is usually a bottleneck step for a successful IVF treatment. What factors control the embryo implantation process has been pursued for many years, and the answers remain largely unknown. PGT-A is a widely applied procedure to identify embryos with normal diploid chromosomes to increase the clinical pregnancy rate per embryo transfer. However, some poor responder patients may only have mosaic embryos that can be used for transfer. We thus investigate the critical regions of the human chromosomes that are important for controlling embryo implantation. Study design, size, duration One hundred and nine mosaic blastocysts were analyzed based on PGT-A assay from 94 patients (ages ranging from 30 to 49 years old, mean age = 38.9 years) undergoing IVF between November 2020 and March 2022. The impact of chromosomal regions on implantation was explored by analyzing the sequencing results together with the pregnancy outcome of mosaic embryos. Additional published outcome data of 1000 mosaic embryo transfers was used to confirm our findings. Participants/materials, setting, methods Pregnant outcomes were followed, including hCG examination, sac formation, and live birth. Whole genome data analysis was performed using individual PGT-A results. Different types of chromosome abnormalities were calculated, and heatmap and clustering analysis were used to define the critical chromosome regions for embryo implantation. In addition, gene set enrichment and pathway analyses were conducted to reveal the functions of genes within the critical regions. Main results and the role of chance Among the transferred 109 mosaic embryos, the clinical outcomes of hCG positive, sac formation, and live birth rates were 45.8%, 42.2%, and 32.1%, respectively. There were 74 (67.8%) and 35 (32.1%) embryos carrying single and multiple mosaic chromosomes, respectively, resulting in 182 chromosomal mosaicism events. The trisomy mosaicism (133/182, 73.0%) occurred with higher frequency than monosomy mosaicism (49/182, 26.9%). Using the heatmap and clustering analysis, our data showed clustered monosomy mosaicism in non-pregnant embryos, especially for chr2, chr4, chr11, chr19, and chr22. Further refinement using segmental mosaic embryos has identified the critical regions, ranging from 10M to 40M in size on different chromosomes that are involved in hundreds of protein-coding genes and known dosage-sensitive genes. Importantly, functional analyses of the genes within the critical regions of chromosome 11 revealed enrichments in embryo invasion and angiogenesis, and suggest that loss of the chromosomal copy of these regions may result in implantation failure. Limitations, reasons for caution It’s still preliminary. More data is required to further confirm the conclusion. Wider implications of the findings Our study provides insights into the chromosomal regions involved in human embryo implantation and will improve the embryo prioritizing strategy in future IVF clinics. Importantly it is the first time the genomics information and gene-mapping strategy have been applied in mosaic embryos to uncover mechanisms underlying human embryo implantation. Trial registration number not applicable

P-248 Egg vitrification related to female age: survival and laboratory outcome of 1233 vitrified-thawed oocytes in non-medical autologous use

Abstract Study question Is the female age at retrieval a determinant factor for the viability and potential of the thawed eggs? Summary answer In patients over 40, thawed oocytes display more abnormal fertilization, develop less in extended culture and yield less top quality blastocyst. What is known already Oocyte cryopreservation is a well-established procedure especially since the advent of the vitrification technique. The successful outcomes achieved with vitrification encourage its application in fertility preservation (FP) for medical and non-medical reasons. Besides, the age-related decline in women’s fertility and the oocyte quality negatively affect the outcome of assisted reproduction. Some studies have reported that age at oocyte retrieval strongly influences reproductive prognosis after FP. However, the appropriate age for non-medical FP is still debated. Although oocyte freezing at a younger age is recommended, there should be a balance between a favourable outcome and the cost-effectiveness of the strategy. Study design, size, duration Retrospective study on 166 patients with frozen-thawed oocytes who underwent ICSI during 2021-2023 in a single hospital. Oocyte vitrification had different purposes: banking for poor responders, to limit the number of embryos, and to solve unexpected situations where partner’s semen sample was unavailable. Patients were divided into three groups according to their age at retrieval (Group A ≤ 37 n = 77, Group B 37-40 n = 44, Group C ≥ 40 n = 45). Post-warming survival, fertilization, and embryological data were studied. Participants/materials, setting, methods 1233 oocytes were thawed. The intact oocytes were microinjected 1-2 hours after warming. Embryos were cultured in Sage 1-StepTM to blastocyst stage, and rated on daily basis. Embryo transfer was performed on day 3 or day 5 and remaining blastocysts were frozen on Day 5 or Day 6. Post warming survival, lysis after ICSI, fertilization, embryo development, blastulation rate (BR) and top blastulation rate (TBR), and morphokinetic features were studied in the 3 groups. Main results and the role of chance 84.6% of the 1233 oocytes (vitrified in a high-security closed system) survived the warming process. 1043 eggs were injected and the post-ICSI lysis rate was 11.2%. No significant differences were seen in thawing survival rate in groups A, B and C (85.6% vs. 83.5% vs. 83.8%, p=0.635) nor in the post-ICSI lysis rate (13.1% vs. 7.4% vs. 11.2%, p=0.072). 2PN fertilization rate was similar between the groups (67.8% vs. 61.3% vs. 67.7%, p=0.178) as well as the total number of embryos (303 vs 146 vs 188 p=0.605). However, triploid fertilization rate (3PN) statistically grew with age (2.8% vs. 5.8% vs. 6.5%, p=0.034). Significant differences were also reported in the global abnormal fertilisation rate (1PN+3PN) (6.4% vs 10.3% vs. 13.3%, p= 0.005). BR and TBR were statistically lower after the age of 40 (BR: 61.5% vs. 62.7% vs 40% p<0.001, TBR: 43.3% vs. 47.9% vs. 24.3% p<0.001). Morphokinetic features in the 3 groups were studied (abnormal cleavage pattern, tSB and tB). Overall results were similar between group A and group B but oocyte potential decreases drastically from the age of 40. Limitations, reasons for caution The major limitation of the study is its retrospective nature and the relative small size of each group. As most of patients were transferred during 2023, the pregnancies have not delivered yet so the live birth rate is not mentioned. Wider implications of the findings Studies have reported the impact of age at oocyte retrieval in case of medical FP in cancer and endometriosis. Here we report a negative effect on outcome after the age of 40 in non-medical FP. Patients should be informed that FP is not a certification of a successful outcome. Trial registration number not applicable

P-735 Is Artificial Intelligence (AI) currently able to provide evidence-based scientific responses on methods that can improve the outcomes of embryo transfers?

Abstract Study question Could chatbots potentially be used as tools for both patients’ and physicians’ education in an infertility journey? Summary answer Artificial Intelligence (AI) is not yet in a position to give clear, evidence-based recommendations in the field of fertility, particularly concerning embryo transfer. What is known already The rapid development of AI has raised questions about its potential uses in different sectors of everyday life. Individuals from diverse fields have tried to incorporate its usage in their personal but also in their professional lives, with varying levels of success. Specifically in medicine, ChatGPT has been studied intensely with more than 400 related articles having been indexed in PubMed until May 2023, while AI has reportedly also succeeded in several standardized medical tests and passed several Medical Board examinations. Hence the question arises whether chatbots could be used as tools for clinical decision-making or patients’ and physicians’ education. Study design, size, duration We used nine of the most popular free AI chatbots available (ChatGPT, Bard, Writesonic, You, Perplexity, Learnt, Bing, Magickpen, and Rytr) and entered the following command: “Write me a 300-word scientific essay about evidence-based methods that can improve the outcomes of embryo transfer” in May 2023. We collected the responses and extracted the methods each chatbot suggested. When sufficient similarity among answers was present we categorized the answers under one category to facilitate the study. Participants/materials, setting, methods We calculated descriptive statistics and the prevalence of each response. We used as a comparator for widely acceptable practices that are proven to improve embryo transfer outcomes the 2017 ASRM guideline on performing embryo transfer taking also into consideration more current literature. Data was compared using chi-squared tests and a level of p < 0.05 was used as the threshold of statistical significance. Main results and the role of chance The range of the recommendations was from one to nine per chatbot (median = 4, IQR = 2) with an average of 4.78 suggestions per chatbot. Out of a total of 43 recommendations, which could be grouped into 19 similar categories, only 3/19 (15.8%) were evidence-based practices, those being “ultrasound-guided embryo transfer”, which was also the most commonly appearing response, appearing in 7/9 (77.8%) chatbots, “single embryo transfer” appearing in 4/9 (44.4%) chatbots and “use of a soft catheter” in 2/9 (22.2%) chatbots. Some controversial responses appeared even more often than the two latter evidence-based ones with “preimplantation genetic testing (PGT)” being the second most common response with 6/9 chatbots suggesting it (66.7%) and the vague suggestion of “optimal endometrium preparation” being in the third place with 5/9 chatbots (55.6%), both non-evidence-based practices to improve embryo transfer. The majority of the recommendations were unique, with 10 answers appearing only once (1/9; 11.1%), those being “endometrial scratching”, “natural cycle embryo transfer”, “use of GnRH antagonist protocol”, “blastocyst transfer”, “use of specialized catheter”, “preimplantation genetic screening (PGS)”, “mock embryo transfer”, “uninterrupted embryo culture”, “minimizing transfer time”, and “maintaining temperature and pH of the culture media”. Limitations, reasons for caution Firstly, we only used some of the most popular chatbots and not all existing ones. Additionally, chatbots tend to give different answers when repeatedly asked the same questions. However, we believe that our study effectively captures the prevailing practices of chatbot users, who typically pose a question only once. Wider implications of the findings Both patients and physicians should be wary of guiding care based on chatbot recommendations in infertility since the majority of responses consists of scientifically unsupported recommendations. Chatbot results might improve with time especially if trained to obtain information from validated medical databases, however, this will have to be verified scientifically. Trial registration number N/A

P-642 The effect of oral dydrogesterone (DYD) on the hypothalamic-pituitary-ovarian (HPO) axis (gonadotropin and sex-steroid levels) and ovulation inhibition: a double-blind, phase I, randomized-controlled, parallel-group trial

Abstract Study question What is the effect of oral dydrogesterone (three cycles daily 20mg/30mg) on pituitary, ovarian and adrenal hormones, ovulation inhibition and endometrium in healthy ovulatory women? Summary answer Daily oral dydrogesterone, 20mg or 30mg, suppresses LH and inhibits ovulation in 33% and 73% of subjects, respectively, while not reducing E2 and other hormones. What is known already Dydrogesterone, a stereoisomer of progesterone, has high oral bioavailability and has demonstrated clinical utility in several indications, including endometriosis and assisted reproduction technologies. Progestin primed ovarian stimulation (PPOS) provides a cost effective and convenient alternative to the GnRH antagonist protocol to suppress a premature LH surge during ovarian stimulation in preparation for frozen embryo transfer IVF. In PPOS, studies have shown that dydrogesterone provides a comparable number of mature oocytes as a standard GnRH antagonist. The effects of various formulations and routes of administration of different progestins on sex hormones and the HPO has not been determined across the indications. Study design, size, duration A single-centre, double-blind, randomised, multiple-dose, parallel-group study of two doses of oral dydrogesterone over three 28-day treatment cycles: dydrogesterone 30mg, 10mg in the morning, afternoon and evening; dydrogesterone 20mg, afternoon dose replaced with placebo. The primary efficacy outcome was the number of subjects with “no ovulation at all” (Hoogland and Skouby score [HSS] 1-4) or “ovulation without pregnancy risk” (HSS 5-6 with negative Landgren criterion) recorded in all treatment cycles. Participants/materials, setting, methods The study population was 44 healthy, pre-menopausal women aged 18–35 years, with proven pre-treatment ovulation. The inclusion/exclusion criteria were defined to reflect the intended target population and the general contraindications for hormonal preparations. The primary objective was to compare the effect of the two self-administered doses of dydrogesterone on ovarian follicular growth leading to ovulation and E2 suppression. Secondary objectives included effect on other HPO hormones, the endometrium, PK characteristics and safety. Main results and the role of chance The number of responders to ovulation inhibition was dose-dependent: DYD 30mg, 72.7%, 95% CI: 49.78–89.27%; DYD 20mg, 33.3%, 95% CI: 14.59–56.97%. Based on HSS and Landgren criteria, there was 42.4% and 15.15% ovulation with pregnancy risk with the 20mg and 30mg doses, respectively. Neither dose had any clinically relevant influence on the average E2 concentration or FSH, androstenedione, dehydroepiandrosterone sulphate, testosterone and sex hormone binding globulin levels, while both doses suppressed the pre-ovulatory LH surge. Endometrial proliferation was mildly suppressed to a comparable extent with both daily doses. Hyperechogenic endometrium pattern was observed in 50% and 72% of treatment cycles in ovulating women in the 20mg and 30mg groups, respectively. Treatment with DYD did not significantly delay follicular growth or postpone ovulation in ovulating women. The more pronounced progesterone suppression with the higher 30mg dose may be due to the higher number of subjects without ovulation and thus without a post-ovulatory progesterone rise in that group. Return of ovulation after treatment cessation occurred in 91% women in the 42-day post-treatment period. The most frequently reported TEAE was ‘ovarian cyst’; all cases were of mild intensity and resolved at the end of the trial. No severe TEAE was reported. Limitations, reasons for caution Only two doses were studied in healthy, ovulatory women. DYD is used in various clinical contexts with concomitant other medications, such as gonadotropins for ovarian stimulation, or under luteotropic circumstances with human chorionic gonadotropin activity from exogenous or endogenous sources. Only limited morning PK sampling was performed. Wider implications of the findings Oral dydrogesterone used for endometriosis symptom reduction may be associated with a low risk of long-term adverse events from hypoestrogenism and suppression of androgens. Oral dydrogesterone displays relevant and short-term effects on LH levels, supporting its use in PPOS protocols. At therapeutic doses, dydrogesterone does not completely inhibit ovulation. Trial registration number EudraCT-No.: 2021-004747-24

P-681 LH priming before ovarian stimulation in POSEIDON-4 patients: effects on oocyte recovery and post ICSI/IVF pregnancy rates

Abstract Study question Can a seven-day long LH priming treatment preceding ovarian stimulation (OS) improve follicular responses, oocyte yields and ICSI/IVF outcomes of POSEIDON-4 patients? Summary answer A seven-day long LH priming can substantially increase pregnancy rates through specific benefits in different subgroups of POSEIDON-4 patients. What is known already The combination of advanced maternal age (AMA) with diminished ovarian reserve (DOR) has become one of the most relevant and complex topics in the field of reproductive medicine. AMA/DOR patients appear to be refractory to increased gonadotropin dose and may benefit from strategies specifically capable of increasing the population of FSH-responsive small follicles before the onset of ovarian stimulation (OS). Androgen mediated LH intra-ovarian activity stimulates early follicular development. Pre-treatment with LH has been suggested to improve ICSI/IVF outcomes in normal responders but has not been assessed in AMA/DOR patients, despite the prevalence and relevance of this population. Study design, size, duration Retrospective cohort study from 2022 to 2023, including 235 POSEIDON-4 patients stimulated with FSH+LH in a flexible antagonist protocol with oestradiol pre-treatment (n = 129) or with the same stimulatory treatment preceded by a seven-day LH priming (150 IU/day) combined with GnRH agonist downregulation (n = 106). Follicular responses, oocyte recovery and ICSI/IVF outcomes were compared between treatment-groups in overall POSEIDON-4 patients and in a subgroup of patients with AMH <0.75 ng/mL (n = 77/Control, n = 59/LH priming). Participants/materials, setting, methods All participants were POSEIDON-4 caucasian patients aged 35 to 44 years undergoing a single homologous ICSI/IVF cycle in our clinic. Outcomes in the form of percentages were compared with the Fisher’s exact test, whereas differences in continuous variables were assessed with the Wilcoxon sum rank test. A multivariate analysis was performed to control for the interference of unequal variations in maternal age, AMH, insemination method and presence of male subfertility. Main results and the role of chance Patients in different treatment groups did not differ (p > 0.05) regarding maternal age (39.2±2.5 vs. 39.3±2.5), basal FSH serum concentrations (11.0±4.6 vs. 10.1±4.3) and antral follicle count (6.3±3.0 vs. 6.4±3.3, for patients stimulated with and without LH priming, respectively), but patients treated with LH priming presented slightly lower AMH serum levels (0.56±0.3 vs. 0.63±0.3; p = 0.05). Nevertheless, patients treated with LH priming achieved a twice higher clinical pregnancy rate per cycle (19.8% vs. 9.3%; p = 0.02), accompanied by a 40% reduction in cycle cancellation (32.1% vs. 45.0%; p = 0.03) and increased production of viable embryos (transferred fresh + frozen) per cycle (1.22±1.09 vs. 0.94±1.07; p = 0.02) and per oocyte inseminated (48.3% vs. 38.5%; p = 0.01), but did not differ regarding follicular outputs or oocyte yield. The multivariate analysis indicated a robust association between LH priming and pregnancy achievement, independently of potential confounding variables (OR = 2.52; p = 0.02). A two-fold increase in pregnancy achievement was also observed in severely restricted POSEIDON 4 patients (AMH <0.75 ng/mL) subjected to the LH priming (p = 0.05), which in this case was accompanied by higher oocyte yields per cycle (3.3±2.8 vs. 2.2±2.0; p = 0.04) and per pick (3.9±2.6 vs. 2.3±2.0; p < 0.01). Limitations, reasons for caution This study is limited by its retrospective nature and the data may be potentially influenced by the use of different downregulation strategies in the treatment-groups, even if the literature indicates equivalent performance for these strategies in the population under analysis. Wider implications of the findings The present data strongly suggest that a seven-day LH priming preceding OS can markedly improve ICSI/IVF outcomes of POSEIDON-4 patients, while indicating that this strategy benefits in different ways subgroups of this increasingly prevalent patient category. These findings thus represent new valuable parameters for the progress of ovarian stimulation. Trial registration number NA

P-734 Low cost antagonist protocol in ivf-icsi cycles using oral ovulation induction agents in developing countries

Abstract Study question The study aimed at comparing the cost-effectiveness of a low cost antagonist protocol using oral-ovulation-induction agents with a standard long GnRH-Agonist protocol in IVF-ICSI cycles. Summary answer Low cost antagonist protocol using oral-ovulation-induction agents comparing with a standard long GnRH-Agonist protocol in IVF-ICSI cycles is cost-effectiveness in developing countries. What is known already IVF-ICSI had always been proved to be costly treatment. The additional expenditure is mainly due to use of high dose of gonadotrophins in order to get more number of eggs. To cut down the cost,low dose or mild stimulation protocol have been popularized all over the world in last few years. Use of aromatase inhibitors along with low doses of gonadotrophins have been an effective means of mild stimulation protocols for IVF cycles. Oral ovulogens, reduces the total dose of gonadotrophin required for inducing follicular maturation. We evaluated if incorporation of letrozole could be an effective alternative for low-cost IVF. Study design, size, duration A total of 304 patients under 40 years of age were studied between 2018 to 2022 Subsequently, they were randomly divided into two groups. The agonist group underwent standard long GnRH analogue protocol. The antagonist group received oral ovulation inducing drugs (CC/Letrozole) and 0.25mg antagonist injections upto the day of hCG injection, using a flexible start approach. Participants/materials, setting, methods A total of 304 patients under 40 years of age were studied between 2018 to 2022. All patients received low-dose OCP before starting treatment. Subsequently, they were randomly divided into two groups. The agonist-group underwent standard long GnRH analogue protocol. The antagonist group received oral ovulation inducing drugs (CC/Letrozole) and 0.25mg antagonist injections upto the day of hCG injection, using a flexible start approach. Follicular development was monitored by vaginal ultrasound and serum estradiol levels. Main results and the role of chance There was a significant difference in the gonadotropin usage between the two groups. As a result, the cost of the CC/Letrozole-gonadotropin-antagonist cycle was significantly lower than the long GnRH agonist-gonadotropin protocol. Though the mean number of oocytes retrieved was higher in the long protocol group, yet the clinical pregnancy rate per transfer was the same in both groups. While comparing for the primary outcomes pregnancy rate and miscarriage rate were comparable between two groups. It is of particular importance to note that despite 60%reduction of total dose of rFSH in the Let-rFSH group,which entailed significant reduction of the cost of treatment, the outcomes in all major aspects including pregnancy rate were comparable between the groups. However, numbers of matured follicles, retrieved oocytes and transferable embryos were not statistically different between study and control group in this study. This prospective study, designed to evaluate the efficacy of oral-ovulogens -FSH as a low-cost IVF protocol, involved an average number of patients; however, the results have been encouraging. We have been successful in reaching our objective to modify an expensive conventional down regulated IVF protocol into one in which the cost was reduced to a larger extent, without compromising the rate of success in developing countries. Limitations, reasons for caution Since last Cochrane review, GnRH-antagonist protocol was proved to be a short and simple protocol with good clinical outcome with significant reduction in incidence of severe OHSS and amount of gonadotrophins requirement. Although, we need more RCTs to come to a conclusion on regular use of such combined protocol. Wider implications of the findings Usage of GnRH-antagonist in combination with Oral-Ovulogens offers the advantage of a low-cost economical stimulation in IVF, as compared to an agonist-protocol, with similar pregnancy-rate in developing countries. It not only offers a cost-saving stimulation-protocol but also reduces side effects like OHSS and multiple pregnancies yet maintain a descent success-rate. Trial registration number not applicable

P-251 Denudation time is crucial to increase the proportion of top-quality embryos in egg donation cycles

Abstract Study question How do different denudation times affect in the efficiency of the egg donation cycles? Summary answer Undetected in vitro matured oocytes, resulting from delayed denudations, contribute to a decreased top-quality blastocyst ratio. What is known already While the timeframe for sperm microinjection in ICSI cycles is widely agreed upon (2-6 hours post-oocyte retrieval), no definitive denudation time preference has been established. Published studies diverge on the advantages of early or late denudation, assessing the impact of trigger-to-denudation time (T-D time) on oocyte maturation. Advocates of early denudation contend it prevents oocyte aging, reducing in vitro culture and enhancing outcomes. These studies, often using data from cycles with own oocytes, exhibit high variability and inconsistent conclusions. The present work introduces an alternative hypothesis on the benefits of early denudation, employing a more stable study model. Study design, size, duration This retrospective study encompasses oocyte donation cycles, employing a short antagonist protocol and ovum pick-up 35.5 hours post-trigger, conducted from January 2019 to July 2023 including 1,559 stimulations. Additionally, 1,275 ICSI cycles without detected sperm pathologies derived from these stimulations were examined to evaluate the influence of T-D time on the reproductive outcomes. Six comparable groups were established by segmenting the sample according to T-D time, annotated in 30-minute intervals (36.5h to 39h). Participants/materials, setting, methods Rates of MII, MI, and nonviable oocytes were examined among 1,559 stimulations resulting in 29,671 oocytes (36.5h:187-stimulations/3,178-oocytes; 37h:226/3,836; 37.5h:614/11,921; 38h:329/6,884; 38.5h:119/2,322; 39h:84/1,530). Additionally, in 1,275 ICSI cycles involving 11,333 MII-oocytes (36.5h:117-ICSI cycles/1,027-MII; 37h:130/1,133; 37.5h:502/4,426; 38h:316/2,925; 38.5h:120/1,041; 39h:90/781), comparisons were made for fertilization, abnormal fertilization, ICSI degeneration, useful day 5/6 blastocyst (transferred or cryopreserved; >3BB-top and ≤3BB-good quality by Gardner score), pregnancy, and live birth rates. Statistics were ANOVA, Chi-square test and Pearson’s correlation. Main results and the role of chance Oocyte maturation profile assessment reveals that groups with later denudation exhibit a higher proportion of MII-oocytes (36.5h:80.71%; 37h:81.04%; 37.5h:81.26%; 38h:80.83%; 38.5h:84.84%; 39h:85.29%; r:0.8475; p < 0.05), reaching significance from 38.5h onward (p < 0.05). This is complemented by a strong negative correlation between T-D time and MI rate (36.5h:5.51%; 37h:5.32%; 37.5h:4.64%; 38h:4.17%; 38.5%h:3.27%; 39h:2.94%; r:-0.9881; p < 0.05), with significant declines at 38h and 38.5h (p < 0.05). No correlation between useless oocytes proportion and T-D time was observed (r:-0.5983; p = 0.21). This illustrates that certain MI-collected oocytes progressively mature during in vitro culture and subsequently, upon denudation, are classified as MII. This overestimates in vivo-matured oocytes. No differences attributed to T-D time were observed regarding fertilization, abnormal fertilization, or ICSI degeneration rates. While time does not affect the rate of useful embryos achieved (36.5h:49.4%; 37h:46.4%; 37.5h:44.6%; 38h:48.0%; 38.5h:50.6%; 39h:47.2%; r:0.1342; p = 0.80), it has an impact on the blastocysts quality. The proportion of top-quality blastocysts (>BB) progressively decreases with T-D time (36.5h:86.2%; 37h:85.2%; 37.5h:85.4%; 38h:81.2%; 38,5h:80.5%; 39h:80.5%; r:-0.925; p < 0.05). Out of 1,794 single embryo transfers, 1,477 have conclusive outcome. No implication of T-D time was detected in pregnancy rate (36.5h:59.88%; 37h:64.07%; 37.5h:61.54%; 38h:65.02%; 38.5h:59.55%; 39h:62.26%; r:0.0489; p = 0.93) or live birth rate (36.5h:40.31%; 37h:51.85%; 37.5h:39.12%; 38h:45.04%; 38.5h:41.83%; 39h:37.96%; r:-0.375; p = 0.46). Limitations, reasons for caution This study has inherent limitations as a retrospective analysis. Additionally, the potential effects of a denudation earlier than 36.5 hours post-trigger, not yet standardized in the laboratory, were not assessed. Wider implications of the findings Delayed denudation may benefit autologous IVF by fostering in vitro oocyte maturation. In egg donation cycles, early denudation is preferable for stringent selection of in vivo matured oocytes, yielding superior results. Additionally, shortening or eliminating incubation periods would enhance the automated sequence of diverse processes during an IVF cycle. Trial registration number not applicable

P-459 Impact of a drop in serum estradiol levels after gonadotropin-releasing hormone (GnRH) antagonist on clinical outcomes of ovarian stimulation cycles in assisted reproductive technology (ART)

Abstract Study question Does a drop in serum estradiol level after the administration of a GnRH antagonist affect outcomes in ovarian stimulation cycles in ART? Summary answer A drop in serum estradiol after administration of a GnRH antagonist is related to changes in luteinizing hormone (LH) and to inferior clinical outcomes. What is known already In recent years, the GnRH antagonist protocol has become widely used to prevent a premature LH surge during ovarian stimulation in ART, with many advantages such as immediate pituitary suppression and a lower risk of ovarian hyperstimulation. However, one phenomenon intriguing professionals monitoring these cycles and reviewing blood analyses, is the decrease in serum estradiol that occasionally occurs after the administration of the antagonist. With the natural menstrual cycle in mind, this could be an undesirable effect possibly affecting clinical outcomes. Study design, size, duration This was a non-interventional, retrospective, observational cohort study. We analyzed 1678 ovarian stimulation cycles in ART in 1143 patients. Patients were treated between January 1st 2015 and November 1st 2022. Patients were 20 to 45 years old, were stimulated with human menopausal gonadotropin (hMG) or recombinant follicle stimulating hormone (follitropin α, β or δ, corifollitropin α and follitropin α + lutropin α) and a GnRH antagonist was used for pituitary suppression in a flexible protocol. Participants/materials, setting, methods Data were extracted from medical records at a tertiary infertility clinic. The difference between serum estradiol level before and after the first antagonist administration was calculated. When this value was negative, the cycle was marked as having an estradiol drop. Influence of treatment and cycle characteristics on estradiol drop, as well as influence of the drop on clinical outcomes were analyzed using generalized linear mixed effects models. Main results and the role of chance The presence of a serum estradiol drop could be calculated in 1552 cycles, of which 153 cycles (9.9%) showed a drop. There was no significant difference in the odds on cycle cancellation between cycles with and without drop (p = 0.87). Type of gonadotrophin used was significantly associated with the presence of an estradiol drop (p < 0.0001), with hMG cycles showing the lowest amount of drops (3.0%). More estradiol drops were observed with the start of antagonist administration on day six of stimulation (10.3% of cycles), compared to starting later than day six (9.1%)(p = 0.001). Serum LH at the start of the cycle was significantly higher in cycles with estradiol drop (mean±SD=4.10±4.13IU/L) than in cycles without (3.88±2.74IU/L) (p = 0.01). Decrease in serum LH levels after antagonist administration was significantly larger in cycles with estradiol drop (-5.30±7.58IU/L versus -1.66±3.13IU/L,p<0.0001). Serum LH on the day of ovulation triggering was also lower in estradiol drop cycles (1.29±1.59IU/L versus 2.24±8.13IU/L,p=0.0007). Estradiol drop was not significantly associated with the number of oocytes retrieved, 2PN fertilized, utilization rate or embryo transfer (p-values>0.05). Ongoing pregnancy and live birth were also significantly lower in cycles with an estradiol drop (13.9%) than in cycles without (25%, p = 0.01). When correcting for age, p-values remained unchanged. Limitations, reasons for caution A limitation of the retrospective study design is that stimulation protocols and any adjustments were chosen by the treating physician according to the patient’s characteristics. The authors did adjust for different cycles per patient by using generalized mixed models. Absolute numbers of estradiol drop are low, limiting optimal multivariable analysis. Wider implications of the findings Because serum estradiol drop after GnRH antagonist administration is related to changes in LH, prospective research could focus on potential optimization of the LH serum levels which could potentially ameliorate clinical outcome. Trial registration number not applicable

P-690 Medroxyprogesterone acetate versus cetrotide in oocyte donation: Non-randomized clinical trial

Abstract Study question Is oral medroxiprogesterone acetate non-inferior compared to cetrotide with respect to the number of mature oocytes retrieved at ovum pick-up in oocyte donation (OD) cycles? Summary answer MPA is comparable to cetrotide in terms of number of mature oocytes (MII) retrieved at ovum pick-up (OPU) in oocyte donation cycles. What is known already Progesterone primed ovarian stimulation (PPOS) uses progestin as an alternative to a GnRH analog for suppressing a premature LH surge during the follicular phase. Published reports indicate that both the number of MII retrieved and pregnancy rates from these oocytes are comparable to protocols using GnRH analogues. Among new stimulation approaches to OD, the use of MPA taken orally has been used successfully, avoiding the need for injecting a GnRH analogue, allowing for more comfortable and cost-effective ovarian stimulation. Another advantage is that vitrification is avoided because the woman undergoing stimulation is not the recipient of the transfer. Study design, size, duration A prospective, non-randomized clinical trial including 23 oocyte donors was performed between February 2020 and February 2021 to evaluate the non-inferiority of MPA (10 mg/day) versus cetrotide (0.25 mg/day) from day 6, in ovarian stimulation cycles triggered with triptorelin acetate. Trigger criterion was ≥6 follicles with a diameter >18 mm Participants/materials, setting, methods All oocyte donors who came for the first time were included. Two OS were performed, the first with a fixed antagonist protocol (hMG and cetrotide), the second PPOS (hMG and MPA). Transvaginal ultrasound was performed, and serum estradiol levels were recorded during monitoring. The main outcome was the number of MII retrieved at OPU. Secondary outcomes were embryological laboratory outcomes and reproductive outcomes in recipients. Main results and the role of chance Basic characteristics, such as age and BMI were comparable, less than 12 months between one donation and another. Duration of stimulation was similar in both OS (10 days), as well as the total gonadotropin dose up to trigger (2544 IU in MPA and 2630 IU in cetrotide). The number of MII retrieved was no different: 11.9 (SD 2.9) with MPA and 10.9 (SD 3.8) in cetrotide (p = 0.5). Recipients and embryo transfer (ET) characteristics were also similar between groups. The mean number of MII assigned to each recipient was 9.2 (SD 2.8) in MPA and 8.2 (SD 3.09) in cetrotide (P = 0.58). MII were fertilized with partner sperm in 93% cycles overall and fertilization rate was 70% in MPA versus 69% in cetrotide (P = 0.61). The number of D5 blastocysts was 4 (SD 2.9) in MPA and 3.56 (SD 2.6) in cetrotide. Overall, there was 99% of double ET and 1% of single ET, with 93.2% of ETs were performed in D5. No significant difference was found in the clinical pregnancy rate 55.3% versus 54.5% (P = 0.785); ongoing pregnancy rate 55.3% versus 50.9% (P = 0.419) and live birth rate 51.1%versus 45.5%, (P = 0.255). Limitations, reasons for caution The patients and physician were not blinded to the study. Further, a large proportion of patients were still pregnant at the end of the clinical trial, therefore live birth rates were not observed in the follow-up period. Wider implications of the findings Ovarian stimulation using MPA for LH surge prevention produces a comparable number of MII oocytes, fertilization rates and live birth rate compared to cetrotide in oocyte donation cycles with the advantage of being a more comfortable and cost-effective ovarian stimulation. Trial registration number Not applicable

P-715 outcomes of in vitro fertilization and embryo transfer among ethnic Tibetan, Yi and Han Chinese women

Abstract Study question Does difference exist in the outcomes of in vitro fertilization and embryo transfer (IVF-ET) among ethnic Tibetan, Yi and Han Chinese women? Summary answer We report that the outcomes of IVF-ET were poorer among ethnic Yi women compared with ethnic Han and Tibetan women. What is known already It has been reported that the outcomes of IVF-ET are correlated with ethnicity/race in Europe and the United States as an independent factor. Sichuan is the only province in China where all 56 ethnic groups reside, with ethnic Han, Yi and Tibetan Chinese having the highest proportions. In Chengdu city (the capital of Sichuan province, basin), the majority ethnic group is Han, whilst in Liangshan and Aba Prefectures (plateau), the major ethnic groups are Yis and Tibetans. The living environment, diet, custom, medical condition and genetic backgrounds are different among different ethnic groups. Study design, size, duration In this multi-center retrospective cohort study, a total of 58374 Chines women aged 20 ∼ 45 had undergoing the first IVF or intracytoplasmic sperm injection (ICSI) ET treatment cycle with non-donor gametes from January 2014 to December 2022 were enrolled. Participants/materials, setting, methods The patients were enrolled from two University Affiliated Hospitals and one Reproductive Hospital in Chengdu. The controlled ovarian stimulation protocols were gonadotropin releasing hormone (GnRH) agonist protocol or GnRH antagonist protocol. The patients were divided into three groups based on their ethnic origins: Tibetans (n = 1069), Yis (n = 2273) and Hans (n = 55032). The outcomes of IVF-ET were compared, with the primary outcome being the live birth rate. Main results and the role of chance The proportion of GnRH agonist protocol and IVF fertilization, the rates of moderate and severe ovarian hyper-stimulation syndrome (OHSS), and cleavage embryo formation in ethnic Han women were significantly higher than in the ethnic Yis and Tibetans (P < 0.05). The rates of implantation, clinical pregnancy and live birth (35.5% vs. 42.4%) were significantly lower, whereas the late abortion rate was significantly higher in Yi women than that in Han women (P < 0.05). The live birth rate was significantly lower in Yi women (35.5%) than in Tibetan (43.3%) and Han women (42.2%) (P < 0.05). Adjustment was made for age, duration, type and etiology of infertility, history of spontaneous abortion, smoking, alcohol, tuberculosis infection, body mass index, antral follicle count, antimüllerian hormone, and so on, by multivariate logistic regression analysis. Yi women had significantly lower rates of moderate and severe OHSS (OR = 0.69, 95% CI = 0.49-0.94, P = 0.024) and clinical pregnancy (OR 0.8, 95% CI 0.70-0.93, P = 0.002) compared with ethnic Hans. Yi women had significantly lower live birth rate compared with ethnic Hans (OR = 0.79, 95% CI = 0.68-0.92, P = 0.002) and Tibetans (OR 0.73, 95% CI 0.58-0.92, P = 0.007). Limitations, reasons for caution The limitations are related with the retrospective study and lack of some demographic characteristics of the patients which may influence the outcomes of IVF-ET, including diet habits, educational level, and economic status. Wider implications of the findings The ethnic group is an independent factor for the outcomes of IVF-ET among ethnic Tibetan, Yi and Han women. Among the three ethnic groups, the Yis had lower live birth rate and moderate and severe OHSS, whilst ethnic Han women had more moderate and severe OHSS. Trial registration number ChiCTR2300070269