Ovarian Cycle Research Articles

O-244 AMH levels in infertile women in APAC region - prospective study in multiple countries, ethnicities and centres

Abstract Secretary General, Asia Pacific Initiative on Reproductive (ASPIRE) President, Taiwan Endometriosis Society Founder & CEO, Taipei Fertility Center AMH is produced by granulosa cells of small growing follicles in the ovary and serum AMH levels strongly correlate with the number of growing follicles, AMH has been used clinically as a marker for ovarian reserve. Despite being of similar ages, with similar AMH levels, durations of ovarian stimulation, and gonadotropin doses, Asian women have been documented as having decreased AFCs and lower yields of total and mature oocytes after ovarian stimulation compared to their Caucasian counter- parts. These earlier data suggested that the effect of ethnicity was as an independent marker of ovarian reserve and potentially subsequent reproductive outcomes. We conducted the first multi-nation, multi-centre, and multi-ethnicity prospective cohort study from January 2020 to May 2021 to investigate serum AMH profiles among infertile Asian women. A total of 4613 women who visited fertility clinics at 12 IVF centres in 11 regions throughout Asia were recruited from Taiwan, China, Hong Kong SAR, India, Indonesia, Japan, Korea, Malaysia (2 centres), Thailand, Vietnam, and Singapore. The inclusion criteria were female partners aged 20–43years and naive to any ovarian stimulation cycle. The AMH measurement was performed using an AMH automated assay on a clinically validated platform. Among the 12 centres that joined the study, most demonstrated racial homogeneity except for Singapore and Malaysia which presented a highly diverse ethnic profile, while others were supposedly monoethnic communities. Unexplained or male infertility is the most common infertility cause in most countries, except for China with a notably high incidence of tubal disease. Age, ethnicity, obesity, and PCOS are significantly associated with ovarian reserve. The highest rates of PCOS were found in Indians (18.6%), Malays (18.9%), and Vietnamese (17.7%), yet remarkably lean with lower obesity rate was found in Vietnamese. Serum AMH levels are not affected by smoking or GnRHa and OCPs pretreatment but are affected by endometrioma surgery. Moreover, the assay can be conveniently conducted on any day of the menstrual cycle and is not influenced by the use of fresh or frozen samples. The rate of decline in ovarian reserve increases with age in Asian women, at 0.13ng/ml/year at 25–33years old and 0.31ng/ ml/year at 33–43 years old. We also found that a cut-off at 4.0 ng/ml could be considered for PCOS diagnosis in the Asian region. Despite limitations, the results can help guide clinicians for personalized infertility treatment, and call for further investigation into the effects of genetic, environmental and lifestyle factors on ovarian reserve.

P-608 Cumulative live birth rates after 3 consecutive embryo transfers in freeze-all cycles following gonadotropin-releasing hormone antagonist protocol versus progesterone-primed ovarian stimulation

Abstract Study question Do cumulative live birth rates in freeze-all cycles differ between gonadotropin-releasing hormone (GnRH) antagonist protocol and progesterone-primed ovarian stimulation (PPOS)? Summary answer GnRH antagonist and PPOS protocols have similar cumulative live birth rates in freeze-all cycles. What is known already GnRH antagonists and progesterone have been used for pituitary suppression in ovarian stimulation cycles. While PPOS protocol has the advantage of oral usage and lower cost, data regarding the laboratory and clinical outcome is limited and confounding. Freeze-all cycles might provide a better model to assess the impact of PPOS protocol and GnRH antagonist protocol on laboratory, clinical outcomes and cumulative live birth rates. Study design, size, duration A retrospective cohort study on IVF cycles performed (n = 568) between January 2020 and May 2022.The entire cohort of embryos were cryopreserved at the blastocyst stage.Inclusion criteria were 18-42 years of age,ICSI for severe male factor infertility.Exclusion criteria were PGD and severe endometriosis.Indications for cryopreservation in the antagonist group were high ovarian response (n:102),endometrial polyps (n:34),high follicular phase P4(n:48) and elective purposes(n:260).PPOS was used due to a transient shortage of GnRH antagonist in the market (n:124). Participants/materials, setting, methods 568 women (GnRH antagonist:444; PPOS:124) were included in the analysis.The primary outcome was the cumulative live birth rate (CLBR) after 3 consecutive embryo transfer cycle, and the secondary outcome parameters were the number of M-II oocytes, fertilization rate and blastocyst utilization rate. Student’s t-test was used for normally distributed continuous data and Fisher’s exact tests for categorical data were used. A generalized estimating equation model and logistic regression analysis were performed to adjust for confounding factors. Main results and the role of chance The mean age of the GnRH antagonist group was 34.1 ± 5.3 and 34.5 ± 5.7 years in PPOS group (p = 0.38). The baseline characteristics including BMI, serum AMH levels, duration of infertility, duration of stimulation and gonadotropin ampules used were similar in both groups. Estradiol and progesterone levels at the time of ovulation trigger were higher in GnRH antagonist cycles (2383.5 ± 1375.4 vs 2034.5 ± 1218.3, p = 0.02 and 0.7 ± 0.6 vs 0.5 ± 0.4, p = 0.01, respectively) The mean number of cumulus-oophorus complexes (12.9 ± 7.4 vs 11.5± 10.0, p = 0.61), M-II oocytes (10.0± 6.1 vs 9.1± 6.1, p = 0.14), frozen blastocysts (4.8± 3.5 vs 4.7± 3.6, p = 0.71) were similar between GnRH antagonist and PPOS groups, respectively. Fertilization rates (84.4% vs 87.2%, p = 0.12) and blastocyst utilization rates (63.4% vs 65.9%, p = 0.34) were also similar between GnRH antagonist and PPOS groups, respectively. The number of transferred embryos and the number of unused blastocysts were similar between groups. The CLBRs after one IVF cycle and 3 consecutive frozen-thawed blastocyst transfers were comparable in GnRH antagonist and PPOS cycles (56.8% and 53.2%, p = 0.37, respectively). Limitations, reasons for caution This was a retrospective study with relatively small sample size performed at a single fertility center, which may limit the generalizability of our findings. Wider implications of the findings If the fresh embryo transfer is not intended, PPOS protocol can be used in all patient types with cost-effective and patient-friendly manner. Trial registration number 2024.013.IRB2.012

P-365 Fertility preservation in patients with borderline ovarian tumors: safety and reproductive outcomes

Abstract Study question Do borderline ovarian tumors (BOT) patients, undergoing controlled ovarian stimulation (COS) face higher recurrence risks, and what are the associated reproductive outcomes? Summary answer Even in advanced-stage or bilateral BOT, COS does not significantly impact recurrence rates. Additionally, COS for fertility preservation(FP)provides a viable option for future reproductive potential. What is known already The primary approach for treating BOTs involves surgical intervention, emphasizing complete tumor removal. Conservative surgery is an option for young women seeking to preserve reproductive potential. However, the recurrence risk following conservative surgery is significant, reaching up to 25%, necessitating repeat surgeries that impact ovarian reserve. Existing evidence on the safety of COS in terms of BOT recurrence remains inconclusive. Concerns about a potential association between COS and tumor progression persist, particularly in advanced-stage and bilateral disease cases. This study address these gaps in knowledge and provide more clarity on the safety of COS in BOT patients. Study design, size, duration A retrospective cohort study was conducted across two tertiary, university-affiliated medical centres: IRCCS San Raffaele Hospital, Milan, Italy, and SHEBA Medical Hospital, Tel-Aviv University, Israel. The study included 165 patients diagnosed with borderline ovarian tumors who underwent conservative surgery between 2012 and 2023. Participants/materials, setting, methods Participants aged 18-42 years with BOT (stages I-III) and undergoing conservative treatment were stratified into two groups: those opting COS for FP(41 patients)and a control group without such intervention (124 patients). COS involved GnRH antagonist random-start protocols utilizing menotropins and/or recombinant FSH. GnRH-agonist or hCG were used for triggering. Oocyte vitrification or fertilization and embryo freezing was performed. Statistical analyses, including Pearson’s chi-square, Fisher’s exact test, T test, and logistic regression, were employed for evaluation. Main results and the role of chance In the course of COS cycles and oocyte retrieval, no complications were observed. Among 165 participants, 33% experienced BOT recurrence over a median of 28.5 months (range: 12.7 to 42.7). Patients with recurrence were younger (29 vs. 32 years, P = 0.04), had advanced-stage (26 vs. 18, p < 0.0001), and bilateral disease (38% vs. 19%, p = 0.01). Of the 41 undergoing COS, 19 experienced recurrence, comparable to the control group (36 patients, p = 0.055). Notably, all COS-related recurrences were BOT histotype, not invasive carcinoma, managed through a second surgery. No significant differences in ovarian stimulation cycles (2.4 vs 1.7, p = 0.7) or retrieved oocytes (11.8 vs 10.6, p = 0.6) were detected between women with and without recurrence. In multivariate analysis, advanced disease significantly increased recurrence odds (aOR=3.7, 95% CI: 1.7-7.9, P < 0.001), while COS did not (aOR=1.7, 95% CI: 0.7-3.9, P = 0.16). This suggests that while age and disease stage play roles, COS alone may not significantly influence recurrence rates. Importantly, among women undergoing COS for FP, 17 achieved at least one pregnancy, totaling 24 pregnancies, with 18 live births. Six were spontaneous, and three used frozen embryos from FP cycles. This underscores the reproductive success of FP through COS, providing hope for fulfilling childbearing desires post-BOT diagnosis. Limitations, reasons for caution Limitations include the retrospective nature, a selection bias in the COS group, and the rarity of the disease leading to a small sample size. Despite these, the recurrence rate in the COS group was comparable to a systematic review, and caution is advised in interpreting these results. Wider implications of the findings Our study suggests that COS does not significantly contribute to recurrence risk in BOT patients, even in advanced stages. FP through COS enhances the likelihood of live births in these patients. While cautious interpretation is warranted, these findings offer hope and call for larger prospective studies to confirm these results. 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-623 Post-market analysis of an AI-powered clinical decision support tool for ovarian stimulation

Abstract Study question How do treatment decisions and patient outcomes change with physician utilization of artificial intelligence (AI) to help determine FSH starting dose and trigger injection timing? Summary answer With physician use of an AI platform, patients were treated with significantly less starting and total FSH without statistically significant changes in outcomes. What is known already Stim Assist is an AI clinical decision support software providing physicians with adjunctive information for the prediction of the number of mature (MII) oocytes that may be retrieved from an ovarian stimulation cycle. The software is intended to assist with the selection of the starting dose of FSH as well as the decision of when to administer the trigger injection. Prior studies have retrospectively estimated the benefit of using AI for treatment decisions during ovarian stimulation, but there is a lack of post-market analyses evaluating the true efficacy of these tools when integrated in clinical practice. Study design, size, duration This study was conducted by multiple physicians at a single IVF clinic in the U.S. The treatment arm consisted of 292 patients seen by physicians using Stim Assist between December 2022 - December 2023. The control arm consisted of 292 matched historical control patients, treated between May 2019 - May 2022 at the same clinic without use of Stim Assist. Participants/materials, setting, methods Matching for each patient was performed for each physician individually, comparing each treatment-arm patient to a historical control-arm patient who was seen by the same physician. Patients were matched 1-to-1 based on age, baseline AMH, and baseline antral follicle count. The primary endpoints were the starting FSH and total FSH prescribed to the patient, as well as MIIs retrieved at the end of stimulation. Main results and the role of chance Comparing the treatment arm to the control arm, the average MIIs were 11.17 vs. 11.45 (p = 0.68), the average starting FSH was 397.09 vs. 443.58 (p < 0.01), and the average total FSH was 4181.77 vs 4601.8 (p < 0.01). The results were stratified by age groups of < 35, 35-40, and >40. For patients in the <35 group (N = 122), the average MIIs were 13.99 vs. 16.06 (p = 0.06), the average starting FSH was 346.72 vs. 380.53 (p < 0.01), and the average total FSH was 3525.84 vs. 3927.25 (p < 0.01). For patients in the 35-40 group (N = 129), the average MIIs were 9.46 vs. 8.71 (p = 0.34), the average starting FSH was 420.35 vs. 486.05 (p < 0.01), and the average total FSH was 4568.6 vs. 5063.37 (p < 0.01). For patients in the >40 group (N = 41), the average MIIs were 8.17 vs. 6.34 (p = 0.12), the average starting FSH was 473.78 vs. 497.56 (p = 0.16), and the average total FSH was 4916.46 vs. 5156.71 (p = 0.34). Limitations, reasons for caution This preliminary post-market analysis was performed at a single clinic in the U.S. We could not calculate live birth outcomes. Due to the limited sample size, differences in outcomes were not statistically significant. Wider implications of the findings These findings suggest that physician use of Stim Assist helped significantly reduce the starting and total FSH prescribed to patients. Additionally, MII outcome differences showed a trend towards an increase in MIIs for patients >35 years old, and a slight reduction in MIIs for younger, better prognosis patients. Trial registration number not applicable

P-713 Proposal of model to calculate the trend in the cumulative live birth rate in IVF cycles using Spanish National Register data from 2009 to 2021

Abstract Study question Is it possible to estimate the trend in the cumulative rate of live births in IVF over 12 years, using data from the Spanish Registry? Summary answer With the proposed formula, a constant increase of 1.7% in the cumulative live birth rate is verified throughout the 12 years of study. What is known already The progressive increase in elective freeze-all cycles no longer allows the use of live birth data by fresh transfer, especially in time series. Cumulative live birth rate (CLBR) has been proposed as an appropriate way of reporting success of an IVF program, incorporating both, fresh and frozen embryos. Nevertheless, views on the most appropriate parameters required to calculate such an outcome have been inconsistent and difficult for national aggregate registries. Furthermore, there is not unanimous definition for its calculation and although IVF Register is mandatory in Spain, an analysis of the CLBR has not been carried out. Study design, size, duration Data from the Spanish National Register of Assisted Reproduction including 456302 women undergoing IVF/ICSI (563000 ovarian stimulation cycles started, 359587 fresh transfers, and 36400 cryotransfer) using autologous gametes performed in Spain from 2009 to 2021 were analyzed. Oocyte donation and PGT-a cycles were excluded. Participants/materials, setting, methods The main outcomes of present study were live birth rate per cycle (LBR) and cumulative live birth rate (CLBR). To obtain the CLBR, the probability of achieving at least one live birth for each cycle started was calculated. This includes both live births after fresh transfer and those achieved after cryotransfer of the embryos obtained from each cycle until they have run out, or a full-term pregnancy is obtained. Main results and the role of chance The live birth rate (LBR) per fresh transfer remains steady (around 24%) throughout the period analyzed. However, LBR for started cycle, which remains constant (17%) until 2013, shows a marked decline since then at a rate of 1% per year. In this same period was observed: a progressive increase in the percentage of cycles with frozen embryos (from 29% to 48%), a greater number of cryopreserved embryos (from 0.9 to 1.6 embryos per started cycle), and a constant decrease in the number of embryos in each cryotransfer (from 2.39 to 1.42). LBR after cryotransfer per started cycle has increased exponentially from 4% to 24%. It was also found a steady increase of the percentage of births after a cryotransfer cycle (from 19 to 70%), surpassing since 2017 those obtained after fresh transfer. To calculate the cumulative live birth rate (CLBR), an algorithm has been developed including all pregnancies that can be achieved with the use of all the embryos obtained after each cycle started until alive child is born. CLBR shows a constant increase in the cumulative delivery rate of 1.7% annually since 2012, rising from 22 % to 35% of births per cycle started. Limitations, reasons for caution One of the main weaknesses of the study is that some patients have not attempted a second or third cryotransfer during the timeframe (for unknown reasons), though they had supernumerary embryos available. However, this model reflects the potential capacity to have at least one living child for each cycle started. Wider implications of the findings The LBR per cycle based only on fresh transfers is not useful for a historical analysis of the effectiveness of the technique. Only the calculation of the CLBR per cycle allows us to understand the real progress of IVF effectiveness in recent years. Trial registration number not applicable

P-710 Comparison of cumulative delivery rates per aspiration cycle in patients fulfilling Bologna and POSEIDON criteria

Abstract Study question Do cumulative delivery rates (CDRs) per aspiration cycle differ in low-prognosis patients according to the Bologna and POSEIDON (Patient-Oriented-Strategies-Encompassing IndividualizeD-Oocyte-Number) classification criteria? Summary answer The CDR was 8.7% in Bologna and 22.7% in POSEIDON. The odds of achieving live-birth were ∼3-fold higher in POSEIDON than in the Bologna group. What is known already Bologna criteria were generated to address the heterogeneity in the definition of the Poor Ovarian Response (POR). However, patients meeting these criteria may not be homogeneous in terms of the number of oocytes retrieved and live birth rate. Subsequently, as a more inclusive classification, the POSEIDON criteria were proposed to stratify low-prognosis patients according to female age and suboptimal response to ovarian stimulation. To our knowledge, there is a paucity of data comparing CDRs between the POSEIDON and Bologna groups. Study design, size, duration Retrospective cohort study including 1250 patients undergoing their first ovarian egg retrieval cycle at Hacettepe University IVF Center in Ankara between 2017 and 2023. Exclusion criteria were female age >45 years old, body mass index >35 kg/m2, azoospermia, pre-implantation genetic testing (PGT) for structural rearrangement or monogenic disorders, fertility preservation cycles, dual-stimulation cycles, premature ovarian insufficiency, and hypogonadotropic hypogonadism. The primary outcome measured was CDR defined by ICMART (International Committee for Monitoring Assisted Reproductive Technologies). Participants/materials, setting, methods The Bologna patients have at least two of the following three features; female-age ≥40 or prior ovarian surgery, AMH<1.1ng/ml or antral-follicle-count (AFC)<5-7, and obtaining ≤3 oocytes in prior conventional stimulation. POSEIDON patients were categorized into four groups; younger(<35) and older(≥35) women with AMH≥1.2/AFC≥5 experiencing an unexpected poor(<4 oocytes-retrieved) or suboptimal(4–9 oocytes-retrieved) response, along with respective younger and older counterparts with AMH<1.1/AFC<5. Non-POSEIDON patients were those with AMH≥1.2/AFC≥5 and >9 oocytes-retrieved. General-Estimated-Equation(GEE) analysis was employed. Main results and the role of chance Out of 1250 patients, 79.6% were classified as POSEIDON, with sub-groups as follows: 5.28% Group 1a, 23.4% Group 1b, 3.6% Group 2a, 10.1% Group 2b, 14.64% Group 3, and 22.48% Group 4. The number of patients meeting Bologna criteria was 17.4% (218). For POSEIDON patients, median[IQR] values were: age 34 [30-38], AMH 1.33 [0.65-2.69], oocytes retrieved 4 [2-6], and embryo transfers 1 [1-2]. For non-POSEIDON patients: age 30 [27-33], AMH 4.63 [2.93-7.07], oocytes retrieved 13 [11-15], and embryo transfers 2 [1-3]. In Bologna patients: age 40 [36-42], AMH 0.46 [0.20-0.76], oocytes retrieved 2 [1-3], and embryo transfers 1 [0-1]. For non-Bologna patients: age 31 [28-36], AMH 2.30 [1.17-4.29], oocytes retrieved 6 [3-9], and embryo transfers 1 [1-2]. CDR for non-POSEIDON: 49.8%; Group 1a, 24.2%; Group 1b, 34.1%; Group 2a, 15.6%; Group 2b, 27.6%; Group 3, 20.8%; Group 4, 10.7%. In clustered-GEE analysis, using non-POSEIDON as reference, odds ratios (ORs) for live birth were: Group 1a OR 0.32 [0.18 - 0.60]; Group 1b OR 0.52 [0.37-0.74]; Group 2a OR 0.19 [0.08-0.43]; Group 2b OR 0.38 [0.24-0.61]; Group 3 OR 0.26 [0.17-0.41]; Group 4 OR 0.12 [0.08-0.19]. CDR for the Bologna group: 8.7% (OR: 0.10, 0.06-0.16); non-Bologna patients: 32.4% [OR: 0.48, 0.39-0.60]. Limitations, reasons for caution The limitations of the study encompass its retrospective cohort design and the variability introduced by different individuals conducting antral follicle counts using 2D ultrasonography. Wider implications of the findings Significant CDR differences exist between Bologna and Poseidon groups. POSEIDON patients show ∼2-fold lower CDR than normal responders, and Bologna patients exhibit ∼4-fold lower CDR than non-Bologna patients. Poseidon criteria cover a broader range of low-prognosis patients, while meeting Bologna criteria indicates a narrower, more specific group with poorer outcomes. Trial registration number N/A

O-009 Comparison of the flexible Progestin-Primed Ovarian Stimulation with the GnRH antagonist protocol in predicted suboptimal responders: a freeze-all randomized controlled trial

Abstract Study question Is the Flexible Progestin-Primed Ovarian Stimulation (fPPOS) non-inferior to GnRH antagonist regarding fertility outcomes in women with a suboptimal response scheduled for freeze-all cycles? Summary answer In predicted suboptimal responders, who do not contemplate a fresh embryo transfer, the ongoing pregnancy outcomes of fPPOS was comparable to that of GnRH-antagonist protocol. What is known already Recent retrospective cohort studies involving donor cycles have demonstrated that Medroxyprogesterone Acetate (MPA) can be effectively and flexibly employed during the mid-follicular phase of the PPOS protocol. This approach prevents premature ovulation without compromising oocyte yields. Given its lesser degree of pituitary suppression, the fPPOS protocol may be particularly relevant for women predicted to have a suboptimal response (defined as AFC < 10) where accumulation of more oocytes could enhance cumulative success rates. Study design, size, duration This is a open-label RCT, performed in a single IVF centre Between July 2019 and June 2023. A total of 484 women scheduled for freeze-all strategy were randomly assigned to fPPOS or GnRH-antagonist protocol. The primary outcome was live birth per woman starting stimulation following18 months of randomization. In this abstract, we present fertility outcomes following the initial frozen embryo transfer (FET) and ongoing pregnancy rates per women within a period of 6 months. Participants/materials, setting, methods Women (AFC<10) referred for IVF/ICSI and did not intend to undergo a fresh transfer, were recruited for this study. MPA (10 mg/day) and Cetrotide (0.25 mg/day) were initiated either when the leading follicle reached 14 mm or on the sixth day of stimulation, whichever occurred first. Due to the COVID-19 pandemic, 22 women withdrew from the study at the stimulation commencement, resulting in 462 women included in the analysis. Data underwent intention-to-treat and per-protocol analyses. Main results and the role of chance No significant difference was observed between the two groups in terms of serum endocrine profiles and stimulation parameters, including the consumption of gonadotropins. Within the 6-month period, 79.5% of women in the fPPOS group and 84.02% in the GnRH antagonist group had undergone at least one cycle of FET (P = 0.234).The ongoing pregnancy rates per women were 48.20% (107/222) in the fPPOS group versus 52.92% (127/240) in the GnRH-anta group (RR: 0.91, 95%CI, 0.76 to 1.09, P = 0.311). There are 62 women who are ongoing pregnancy but do not reached live birth during the follow-up period. Regarding the outcomes of the initial FET cycle, there was no difference in the ongoing pregnancy rate between the two groups (49.01% vs 48.37%, RR: 1.03, 95% CI, 0.81 to 1.26, P = 0.908). Other outcomes including biochemical pregnancy rate (62.25% vs 63.59%), clinical pregnancy rate (60.26% vs 57.61%), and miscarriage rate per pregnancy (16.48% vs 15.09%), also exhibited no significant differences. The number of oocytes retrieved, two-pronuclear oocytes, viable and high-quality embryos, as well as the total number of embryos cryopreserved were also similar between groups. There was one case of premature ovulation in the fPPOS group and none in the GnRH-ant group. Limitations, reasons for caution Due to the distinct administration routes of the medications, blinding was not feasible in this open-label trial, which may affect the assessment of outcomes. All participants were recruited in a single center from one country, limiting the generalizability. In this abstract, we only report on the ongoing pregnancy outcomes. Wider implications of the findings This is the first freeze-all RCT comparing the long-term outcomes of fPPOS and GnRH antagonist in autologous ovarian stimulation cycles. Eliminating the variability of fresh and frozen transfers, the fPPOS seems an efficacious alternative for women with predicted suboptimal response, when a GnRH antagonist would have been the preferred regimen. Trial registration number ChiCTR2000030356

O-221 An interpretable deep learning model for predicting the number of mature oocytes retrieved after ovarian hyperstimulation

Abstract Study question Can an interpretable deep learning model successfully predict the number of mature oocytes retrieved after ovarian hyperstimulation and provide the rationale for these predictions? Summary answer An interpretable deep learning model can successfully predict the number of mature oocytes retrieved and provide a rationale for these predictions. What is known already A number of recent studies have used classical machine learning models in order to predict the number of mature oocytes retrieved in IVF cycles, including XGBoost, RandomForests and even basic deep learning models such as feed forward networks. Although these studies predicted the number of mature oocytes with a relatively high performance, the employed methods lack insights into the rationale governing their predictions. This lack of interpretability poses an important limitation when applying these models in a clinical setting. Study design, size, duration This study was a retrospective analysis of a dataset of 6,430 ovarian stimulation cycles performed at a single center in the USA, aimed at building a deep learning based, interpretable model to predict the number of mature oocytes retrieved after ovarian hyperstimulation. Participants/materials, setting, methods An interpretable deep learning model was developed to predict the number of mature oocytes retrieved. The model was evaluated on an out-of-sample test set and compared to baseline models used in prior studies such as XGBoost and Linear Regression. Main results and the role of chance The model successfully predicted the retrieved oocyte count, with a mean absolute error (MAE) deviation of ± 3.14 oocytes from the ground truth. The model outperformed the performance of models used in previous studies such as XGBoost and Linear Regression which achieved a MAE of ± 3.16 and ±3.2 oocytes respectively on the test dataset. Parameter significance was measured by calculating how much parameters aided in the final prediction. The parameters found to be most significant in predicting the number of retrieved mature oocytes were (in order): total number of follicles, number of follicles size 12mm-15mm and number of follicles size 16-17mm. Parameters that were found to be of lower significance but still indicative were follicles larger than 18 mm and estradiol on trigger day. Surprisingly, age and basal FSH were of little significance. Most notably, the number of follicles in the 12mm -15mm bin were much more indicative than larger follicles of size 16-17mm and much more than follicles larger than 18mm. Furthermore, the model generates a transparent breakdown of the prediction for each patient, including a heat map and bar graph highlighting the factors influencing the decision making process at every step, creating a completely transparent prediction process. Limitations, reasons for caution The model was developed on training data from a single clinic, therefore requiring further data collection from diverse global locations to ensure the model’s ability to generalize. Wider implications of the findings This study demonstrates better oocyte prediction accuracy and transparency in the prediction process, surpassing previous models while also building trust. These advancements not only improve the safety of Artificial Intelligence tools for optimizing stimulation protocols but also contribute to reducing regulatory concerns surrounding their deployment in clinical settings. Trial registration number not applicable

O-089 Association of pituitary suppression method with euploid blastocyst yield in preimplantation genetic testing for aneuploidy (PGT-A) cycles

Abstract Study question Do progestin primed ovarian stimulation (PPOS) cycles have lower euploidy yield compared to pituitary suppression with gonadotropin releasing hormone (GnRH) antagonists? Summary answer The choice of pituitary suppression method has no bearing on euploid retrieval per blastocyst tested. What is known already Progestin primed ovarian stimulation cycles are an alternative to GnRH antagonists when fresh embryo transfer is not a priority. While the two approaches have been shown to be similar in terms of conventional stimulation outcomes such as mature oocyte retrieval, and blastulation rates, there is still some lingering controversy regarding cumulative pregnancy rates and the effects of progestins on embryo genetic constitution. Study design, size, duration This was a multicenter retrospective cohort study including data from two tertiary-level treatment centers. Participants/materials, setting, methods Infertile women undergoing ovarian stimulation with either progestin primed or GnRH antagonist pituitary suppression with the intention of transfer after PGT-A embryo testing with next-generation sequencing. The main outcome parameter was euploid embryo count per blastocyst tested and was modeled with mixed-effects log-binomial regression models. Results were adjusted for patient age and laboratory performing the PGT-A tests while they were not adjusted for embryo quality to avoid collider bias. Main results and the role of chance A total of 1425 PGT-A tested blastocysts from 383 cycles of 365 patients were included in the analysis. 243 cycles (63.4%) received GnRH antagonists for pituitary suppression while 140 (36.5%) received progestins. The overall euploidy rates per blastocyst tested in the GnRH antagonist and PPOS groups were 38.8% vs. 31.1%, 30.2% vs. 29.4%, 27.0% vs. 25.2%, and 13.8% vs. 14.5% for the age categories <35, 35-37, 38-40, and >40, respectively. After adjusting for the effect of female age at testing and the laboratory performing the PGT-A test, the type of pituitary suppression was not significantly associated with euploid retrieval per blastocyst tested (adjusted risk ratio: 0.94, 95% CI: 0.70 - 1.28, P = 0.701). After testing, 191 women received 233 embryo transfers. Human chorionic gonadotropin (hCG) positivity per transferred embryo was not significantly different between progestin primed and GnRH antagonist cycles (RR: 0.89, 95% CI: 0.71 – 1.08, P = 0.268). Limitations, reasons for caution This is a retrospective study with data from multiple centers with a non-standardized selection of blastocysts to be tested. In addition, the sample size and retrospective nature of the data may have biased the estimates. Wider implications of the findings The choice of pituitary suppression method does not appear to have a significant effect on euploid embryo retrieval rates or hCG positivity per transfer. The choice of medication can be based on the needs of the individual case without concern for suboptimal PGT-A outcomes. Trial registration number Not Applicable

O-014 Cumulative live birth associated with number of oocytes in ovarian stimulation with follitropin delta: an individual patient data meta-analysis

Abstract Study question What is the optimum number of oocytes retrieved to maximise cumulative live birth rates in the fresh and subsequent frozen cycles following follitropin delta stimulation? Summary answer The cumulative live birth rate increased steadily with number of oocytes retrieved up to a plateau starting at ∼21 oocytes retrieved. What is known already Live birth rate (LBR) per fresh ovarian stimulation cycle is the conventionally reported outcome of in vitro fertilisation (IVF). In recent years, there has been a marked increase in number and successful outcomes of cryopreserved cycles, suggesting that the cumulative live birth rate (CLBR) has emerged as a more clinically relevant outcome. In the fresh cycle, the number of oocytes retrieved is regarded as a prognostic factor for LBR. A similar association has been shown for CLBR implying that CLBR increases with the number of oocytes and continues to increase beyond the plateau observed for fresh cycle LBR. Study design, size, duration Individual patient data meta-analysis of 1746 patients from 4 randomised controlled trials using follitropin delta for ovarian stimulation. The analysis included patients with ≥1 oocyte retrieved following stimulation. The CLBR in the fresh and subsequent frozen cycles was evaluated. Predicted CLBR was obtained using a logistic regression analysis with fractional polynomials to assess the association between number of oocytes retrieved and CLBR. Subgroup analyses were performed based on age, AMH and number of oocytes retrieved. Participants/materials, setting, methods Participants were women, 18–42 years, undergoing their first or second in vitro fertilisation/intracytoplasmic sperm injection (IVF/ICSI) cycle in a GnRH antagonist/long agonist protocol with human chorionic gonadotrophin or GnRH agonist triggering and IVF/ICSI insemination. Single or double blastocyst transfer was performed on Day 5 and all viable surplus blastocysts were cryopreserved. All pregnancies from the fresh cycle and frozen cycles initiated within 1 year after start of stimulation were followed until birth. Main results and the role of chance The study included 1746 patients who underwent a total of 2948 cycles; 1746 fresh and 1202 frozen. In total, 740 patients (42.4%) initiated frozen cycles (maximum of 6). The study population had a mean age of 33.8 years and a median AMH level of 17.0 pmol/l. The mean number of oocytes retrieved was 12.4, the fresh cycle LBR was 29.1% and the CLBR was 51.4%. The CLBR steadily increased with number of oocytes retrieved, reaching above 60% at > 15 oocytes and above 70% at > 20 oocytes. The CLBR started to plateau at ∼21 oocytes. Subgroup analyses by number of oocytes retrieved, age group or AMH group demonstrated that the CLBR decreased with increasing age (57.1%, 51.6% and 35.8% at < 35, 35-37 and ≥38 years). In comparison it was similar for AMH <15 and ≥15 pmol/l (52.0% and 50.9%, respectively). A continued increase in CLBR from 15 oocytes retrieved was observed in older patients (≥38 years); from 41.3% to 53.4% to 58.7% at 15-19, 20-24 and ≥25 oocytes. No equivalent benefit was observed in younger patients, where corresponding rates were 72.5%, 68.0% and 78.8% in patients <35 years, and 70.3%, 73.1% and 71.5% in patients 35-37 years. Limitations, reasons for caution A limitation of this study is the small number of patients with >20 oocytes retrieved. The individual pooled studies were heterogenous regarding number of blastocysts transferred and hCG/agonist trigger. Wider implications of the findings The current individual patient data meta-analysis suggests an increase in CLBR with number of oocytes retrieved up to a plateau starting at ∼21 oocytes following ovarian stimulation cycles with follitropin delta and subsequent frozen cycles. An increase in CLBR from 20 oocytes was evident in older but not younger patients. Trial registration number NCT01956110, NCT03564509, NCT03740737, NCT03738618

P-595 Increased clinical pregnancy rates using a clinical decision support tool - a retrospective cohort study

Abstract Study question Does using a clinical decision support tool, Opt-IVF, to guide hormone dosing during superovulation yield increased clinical pregnancy rates in routine clinical practice? Summary answer Higher clinical pregnancy rates were obtained using Opt-IVF to guide stimulatory hormone dosing during superovulation. What is known already ART success rates and cost depend heavily on the superovulation stage of the cycle. Two prospective single-center trials and one prospective multi-center trial had shown that using Opt-IVF to guide dosing resulted in increased numbers of high-quality embryos, used lower hormone doses, and required less ultrasound testing. This is a retrospective cohort study of the use of Opt-IVF in clinical practice over 12 months compared with the control cohort from the previous 12 months. Study design, size, duration Design: The study examined patients undergoing an IVF cycle using Opt-IVF in a single center for 12 months. Opt-IVF was used in all patients who presented to one of the investigators at Akanksha Hospital during the study period. As a comparison group, we examined patients from the previous 12 months when Opt-IVF was not used, and standard clinical protocols were followed to guide dosing. Duration: The study was conducted over 24 months Participants/materials, setting, methods 204 women aged 25-45 years underwent superovulation using hormone doses suggested by Opt-IVF (intervention). Of the participants, 19% were poor responders, 74% were below 35 years of age, 19% were 35-39 years of age, and 7% were above 39 years of age. The control group included 207 women, of whom 10% were poor responders. 72% were below 35 years of age, 26% were 35-39 years, and 2% were above 39 years of age. Main results and the role of chance The participants in the intervention group required significantly lower cumulative gonadotropin dosage compared to the control group during their controlled ovarian stimulation cycles (p < 0.0001). The average number of total embryos was 20% higher (p < 0.001), and the average number of good-quality embryos was 50% higher (p < 0.0001) in the Opt-IVF group than in the control group. Only 4.9% of cycles were canceled in the intervention group, compared to 12.9% canceled in the control group. Overall, Clinical pregnancy rates (including canceled cycles) increased from 35 % in the control group to 43% in the intervention group. The clinical pregnancy rate for poor responder patients was 39% in the Opt-IVF group but was only 16% in controls (p < 0.0001). Similarly, the clinical pregnancy rates were 34% in patients ages 35-39 years and 33% in patients above 39 years of age, much higher than the corresponding clinical pregnancy rates in controls (27% and 0%, respectively). Higher clinical pregnancy rates were also noted in the intervention group for normal responders and for younger patients. Limitations, reasons for caution This is a single-center retrospective cohort study. Wider implications of the findings Using Opt-IVF to guide dosing resulted in increased numbers of high-quality embryos and higher clinical pregnancy rates, particularly among older patients and poor responders. The proportions of these patients can be expected to grow in the future, so improving results in such patients is essential. Trial registration number not applicable

P-536 Preimplantation Genetic Testing for hereditary breast and ovarian cancer syndrome due to BRCA pathogenic variant : the parisian center experience

Abstract Study question What are the outcomes of Preimplantation genetic testing for monogenic disease (PGT-M) for BRCA pathogenic variants? Summary answer Among couples entering a PGT-M program for BRCA pathogenic variants, 23.5% achieved a live-birth. What is known already BRCA pathogenic variants are associated with an oncologic predisposition with variable penetrance and are accessible to screening and preventive procedures to avoid or early detect the development of cancer. Transmission of BRCAmutations to offspring poses a significant reproductive concern for BRCA mutation carriers. PGT-M offers a solution to prevent this mutation transmission. Despite reproductive challenges related to BRCA status, there are no existing international guidelines for applying PGT-M in these situations. In France, authorization for BRCA related PGT-M is case-specific, considering the personal and familial severity of the disease and submitted to a multidisciplinary prenatal diagnosis center (CPDPN). Study design, size, duration This retrospective observational study, is a single-center analysis of 46 requests for PGT-M related to BRCA pathogenic variants at our PGT center from January 2015 to December 2022. Participants/materials, setting, methods Forty-six couples asked for PGT-M for BRCA pathogenic variant carried by one of the partner. The present study involves the examination of data encompassing referrals, decisions as well as clinical outcomes associated with PGT-M. Main results and the role of chance Forty-six requests for PGT-M due to the risk of hereditary predisposition to breast and ovarian cancer have been received: 36 for a pathogenic variant in the BRCA1 gene and 10 for BRCA2. Nine couples ultimately did not proceed and dropped out. Eight requests were declined, either due to the refusal of the multidisciplinary prenatal diagnosis center (CPDPN) based on family history (n = 4) or alteration of ovarian reserve (n = 4), the 2 latter requests are still under investigation. In total, requests from 27 couples (55%) were considered eligible and feasible. Among them, 17 (63%) underwent at least one PGT-M cycles (5 dropped out before the beginning and 5 are still pending). Overall, 33 ovarian stimulation cycles for in vitro fertilization were initiated, resulting in the retrieval of 192 mature oocytes and the formation of 145 embryos. Of these, 97 were biopsied, and 38 did not carried the BRCA pathogenic variant. A total of 21 fresh or frozen embryo transfers were performed and 8 pregnancies were achieved, leading to 4 deliveries and 5 live births (23.5% of couples who started a PGT-M cycle). Limitations, reasons for caution In the absence of established guidelines, there is variability in information regarding PGT-M among oncogeneticists. Thus, only selected carriers of BRCA pathogenic variants are addressed to our PGT centers. Additionally, women participating in a fresh PGT cycle were selected on several criteria including ovarian reserve parameters. Wider implications of the findings PGT-M provides a viable alternative for couples seeking to prevent the transmission of BRCA mutations. To increase the PGT-M cumulative live birth rate, the transfer of male embryos carrying the variant, assumed to have lower tumor risks, should be considered and discussed with patients. Trial registration number Not applicable

O-302 Feasibility and efficacy of a flexible and simplified ovarian stimulation protocol for oocyte donors, combining random-start corifollitropin alpha and progestin primed ovarian stimulation protocol (PPOS)

Abstract Study question Is the total number of retrieved oocytes in donors equivalent, according to the onset phase of stimulation with corifollitropin alpha in a random-start PPOS protocol? Summary answer The total number of retrieved and mature oocytes were not different after starting stimulation in the early, mid or late follicular or luteal phases. What is known already Recent studies have shown the ability to obtain oocytes of equivalent quality after follicular or luteal phase ovarian stimulation and have also demonstrated the efficacy and safety of the PPOS protocol in oocytes donors. In order to provide a more friendly, simplified and flexible ovarian stimulation protocol reducing the burden for donors, we studied the impact on oocyte yield of combining a random start corifollitropin alpha stimulation with the concomitant prevention of premature LH surge by progestin administration. Study design, size, duration This multicenter open-labelled RCT was performed in 4 oocytes donation centers from July 2020 to September 2023 to assess the equivalence in terms of number of retrieved oocytes of a delayed onset of corifollitropin alpha stimulation with concomitant administration of desogestrel in Mid Follicular Phase (MFP/D4-D7 of the natural cycle), Late Follicular Phase (LFP/D8-D11), Ovulatory Phase (OP/D12-D15) or Luteal Phase (LP/D16-D30) compared to the standard start in Early Follicular Phase (EFP/D1-D3). Participants/materials, setting, methods From 110 randomized oocyte donors,102 reached triggering of ovulation with triptoreline acetate and OPU : EFP n = 22, MFP n = 20, LFP n = 19, OP n = 18 and LP n = 23. The sample size was calculated to show an equivalence between groups in total number of retrieved oocytes. Secondary endpoints were the number of mature oocytes, premature LH surge and Ovarian Hyperstimulation Syndrome rates. Differences were tested using a ANOVA test or a Pearson’s Chi2 test, as appropriate. Main results and the role of chance Donors were 33 [29.2-35.0] years old [95% Confidence interval] with a mean BMI of 23.4 [21.1-26.3] kg/m2. The mean number (SD) of retrieved oocytes was 14.2 (9.1). In intention to treat analysis, there was no significant difference between the 5 groups, regarding the total number of retrieved oocytes. The mean numbers of retrieved oocytes from the 5 groups were 12.5 (7.7), 13.2 (8.0), 15.7(9.8), 17.8 (11.4), and 12.8(8.3), respectively in the EPF group, the MPF group, the LPF group, the OP group and the FP group, with no significant differences between the groups (p = 0.30). The mean (SD) number of mature oocytes was 11.8 (7.6) with no significant differences between the 5 groups. Only one premature LH surge was reported in the MFP group (0.98%). Four minor to moderate OHSS were reported (3.9%). Limitations, reasons for caution The main limitation of our study is the small sample size responsible for a lack of power. But to our knowledge, this is the first RCT to compare the number of oocytes retrieved, according to the onset phase of ovarian stimulation in a random-start PPOS protocol, for oocyte donors. Wider implications of the findings The proportion of ovarian stimulation cycles with freeze-all is constantly increasing worldwide. Therefore simplified, ultra-flexible ovarian stimulation protocols could be proposed to maintain the spread of the workload along the working days without programming, with fewer injections and reduced burden for patients, with the same efficacy. Trial registration number NCT03895099

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

P-604 Underlying molecular mechanisms of Polycystic Ovary Syndrome and Morphology: focusing on the ovary

Abstract Study question What mechanisms are involved in the ovarian alterations of Polycystic Ovary Syndrome (PCOS) and Morphology? Summary answer PCOS patients associated a distinctive impairment of oxidative phosphorylation and dysregulated complement system in their follicular compartments not found in Polycystic Ovarian Morphology (PCOM) women. What is known already PCOS is a major cause of female infertility characterized by aberrant follicular development and hormonal imbalances leading to reproductive symptoms such as anovulation, poor oocyte quality, and hyperandrogenism. Likewise, PCOM is present in 16-25% of women with regular menses, but the clinical relevance of this ovarian phenotype and its correlation with PCOS remains unclear. Therefore, to establish the specific molecular mechanisms underlying the ovarian alterations in PCOS using High-throughput techniques will allow us to provide a better clinical management and a differential diagnosis with PCOM women. Study design, size, duration Cross-sectional molecular study including samples from 26 patients undergoing an IVF cycle between 2019-2022 at Hospital La Fe (Valencia, Spain). Eight women were considered PCOS, eleven PCOM and seven were control fertile patients. Granulosa cells (GCs) and follicular fluid (FF) samples were obtained during oocyte retrieval to perform RNA-seq and proteomic analysis, respectively. Participants/materials, setting, methods Women with two or more Rotterdam-criteria were considered as PCOS, while PCOM was defined by polycystic ovarian morphology on ultrasound with regular ovulatory cycles. RNA from GCs was obtained and sequenced using NextSeq500-Illumina to identify differentially expressed genes (DEGs) using DESeq2 (R-software). The proteome of FF samples was established by LC-MS/MS and differentially expressed proteins (DEPs) analyzed with limma package. Functional enrichment analysis of DEGs and DEPs (FDR< 0.05) was performed based on KEGG database. Main results and the role of chance RNA-seq data revealed clear distinctions between GCs from PCOS and control women, with 526 DEGs. By contrast, the transcriptomes of PCOS and PCOM were more similar, with only 34 DEGs. Notably, oxidative phosphorylation emerged as the most enriched pathway in both comparisons, showing a differential expression in PCOS. Indeed, 6 out of 12 shared DEGs (MT-TP, MT-ND4L, MT-ND2, MT-ATP8, MT-ND4, and MT-ATP6), were mitochondrial genes found upregulated in PCOS vs. PCOM and control samples. These findings suggest that granulosa cells from PCOS present a dysregulation in oxidative phosphorylation, potentially linked to alterations in those genes associated with the mitochondrial electron transport chain. The proteomic analysis showed 37 DEPs in the FF of PCOS compared with controls, being these DEPs mainly involved in the complement and coagulation cascades, PI3K-AKT pathway, oocyte meiosis and ferroptosis. Furthermore, the PCOS vs. PCOM analysis revealed 42 DEPs, significantly enriched also in complement and coagulation cascades, ferroptosis and glutathione metabolism. Interestingly, fifteen proteins were differentially expressed in both comparisons, with four of them related to the complement system (PROS1, C1S, C1QB and MASP2), suggesting that an alteration in this system at follicular fluid level might be one of the hallmarks of PCOS. Limitations, reasons for caution Further experimental studies are required to validate the specific changes identified in our study. Moreover, to establish how these alterations in the follicular compartments affect the oocytes of PCOS patients should also be explored. Wider implications of the findings Our study focused on specific mechanisms involved in PCOS ovarian alterations, providing new insights into potential biomarkers for an accurate diagnosis and management of this pathology. Dysregulations in oxidative phosphorylation and complement system might play a crucial role in PCOS multifactorial nature, contributing to impaired folliculogenesis and decreased oocyte quality. Trial registration number Not Applicable

O-031 Tacrolimus treatment significantly improved IVF outcomes with euploid embryo transfer in women with repeated implantation failures (RIF) and elevated T helper (Th)1/Th2 cell ratios

Abstract Study question Dose tacrolimus improve implantation rate for RIF women showing elevated T helper (Th)1/Th2 cell ratios, particularly those undergoing IVF/ET with euploid blastocysts? Summary answer Tacrolimus improved the implantation rate in RIF women with elevated Th1/Th2 cell ratios undergoing IVF/ET using euploid blastocysts. What is known already The peripheral blood Th1 and Th2 cells determine immune inflammatory responses at the maternal-fetal interface. Previously, we reported that about 40% of women with RIF (≥4) had elevated Th1/Th2 cell ratios (≥10.3). The pregnancy rate was significantly improved when they were treated with tacrolimus, an immunosuppressive agent [AJRI 2015]. However, genetic embryonic concerns of RIF could not be ruled out since not all transferred embryos were genetically screened. Recently, we reported an adjusted cut-off value of the Th1/Th2 cell ratios (≥11.8) [AJRI 2021] for women with RIF based on the retrospective analysis. However, the prospective study has not been performed. Study design, size, duration A prospective cohort study was performed, including 569 infertile women with more than 4 times of RIF. The study participants received ET with euploid blastocysts from September 2020 to November 2021. All transferred blastocysts were confirmed as euploid or low-frequency mosaic by preimplantation genetic testing for aneuploidy, and the endometrial preparation for ET was made by using either hormone replacement cycle or natural ovulatory cycle. Participants/materials, setting, methods Before ET, all participants were measured for their peripheral blood Th1/Th2 (CD4+IFN-γ+/ CD4+IL-4+) cell ratios in the secretory phase. Women who had elevated Th1/Th2 cell ratios (≥10.3) received tacrolimus (2-4 mg daily). Tacrolimus was started 2 days before ET, and the hCG and gestational sac (GS) rates were calculated in women with or without tacrolimus. Main results and the role of chance Of 569 participants, 174 (30.6%) women showed elevated Th/Th2 cell ratios (≥10.3), whereas the remaining 395 women served as control (Control group). Among 174 women, 148 women received tacrolimus (Tac group), while 26 did not receive tacrolimus (no-Tac group). The hCG and GS rates of the Tac group were 73.0% and 64.2%, respectively, similar to the no-Tac group (69.2% and 57.7%, respectively, P=NS). Meanwhile the hCG and GS rates of the control group were 70.6% and 60.0%, respectively (P=NS). When the Th1/Th2 cell ratio cut-off value was set to ≥ 11.8, 123 women of the 569 participants (21.6%) had elevated Th1/Th2 cell ratios (≥11.8). Among them, 112 received tacrolimus (Tac2 group), and 11 did not tacrolimus (no-Tac2 group). The remaining 410 women were as a control group (Control2 group). The GS rate of the Tac2 group was 67.0%, which was significantly higher than that of the no-Tac group (36.3%, p < 0.05), while the GS rate of the Control2 group was 60.5% (P=NS, vs Control2 group). Tacrolimus dosing data was as follows; 11.8 or more but less than 15.8 of Th1/Th2 cell ratios were needed for 2 mg of tacrolimus daily, and 15.8 pr more was needed for 3 mg of tacrolimus. Limitations, reasons for caution The study was a controlled trial with a limited number of study population. Additionally, the endometrial changes or peripheral immune responses after tacrolimus were not evaluated thoroughly. Further study is needed for the tacrolimus effect on systematic immune responses and local endometrial immune milieu. Wider implications of the findings Before ET, screening for increased Th1/Th2 ratios (Cut-off value ≥11.8) may significantly improve IVF outcomes by selecting proper candidates for tacrolimus treatment and detecting the proper tacrolimus doses. Notably, a significant proportion of women with RIF have additional implantation failures, even with euploid embryos, when immune-inflammatory conditions were not controlled. Trial registration number not applicable

O-061 Ovarian cancer and fertility - current understanding

Abstract Introduction Ovarian cancer is a significant health concern worldwide and is the leading cause of death from gynecologic malignancies. While fertility preservation is essential for many young women diagnosed with cancer, concerns have been raised regarding the potential impact of fertility treatments on the risk of ovarian cancer development. 1. Ovarian Cancer Risk Factors Ovarian cancer is a multifactorial disease with various risk factors contributing to its development. A woman has a risk of 1 in 78 of having ovarian cancer in her life time, risk factors include: • Age: Ovarian cancer risk increases with age, with the highest incidence observed in women over 50 years old. About 12.1% of Ovarian Cancer patients are younger than 44 years old. • Family History: Women with a family history of ovarian or breast cancer, especially first-degree relatives, have an increased risk. • BRCA Mutations: Inherited mutations in BRCA1 and BRCA2 genes significantly elevate the risk of ovarian cancer. • Reproductive Factors: Factors such as nulliparity, early menarche, late menopause, and infertility have been associated with an increased risk of ovarian cancer. 2. Fertility Treatments and Ovarian Cancer Risk Understanding the mechanisms underlying ovarian cancer development is crucial for assessing the potential impact of fertility treatments : • Ovulation Hypothesis: The repeated ovulation theory suggests that each ovulatory cycle increases the risk of DNA damage to ovarian epithelial cells, potentially leading to cancer development. The use of fertility drugs to stimulate ovulation, such as clomiphene citrate and gonadotropins, has been studied , the early studies suggested a potential increased risk, more recent evidence has been conflicting, with some studies reporting no association. • In Vitro Fertilization (IVF): Several large-scale studies have investigated the relationship between IVF and ovarian cancer risk found no significant increase in ovarian cancer risk . • Hormonal Influence: Fertility drugs alter hormonal levels, particularly estrogen and progesterone, which may influence ovarian cancer risk. • Selection Bias: Some studies have suggested that the ovarian cancer risk may be confounded by underlying infertility factors rather than the treatments themselves. 3. Clinical Implications and Recommendations • Individual Risk Assessment: Clinicians should assess each patient's individual risk factors for ovarian cancer, including age, family history, and reproductive history, before initiating fertility treatments. • Informed Consent: Patients should be provided with comprehensive information regarding the potential risks and benefits of fertility treatments • Regular Surveillance: Women undergoing fertility treatments should receive regular gynecologic screenings and follow-up care to monitor for any signs or symptoms of ovarian cancer. • Shared Decision Making: Shared decision making between patients and healthcare providers is essential to ensure that treatment decisions align with patients' preferences and values. 4. Fertility Preservation Options • Most therapeutic options for Ovarian Cancer cause infertility, either by premature ovarian failure caused by cytotoxic agents in chemotherapy or surgical approaches that include unilateral or bilateral oophorectomy • In ovarian cancer patients, Oocyte cryopreservation is still the best option and the only one established along with embryo cryopreservation. Fertility preservation surgery can be suggested depending on histology, stage of disease and pre-existing ovarian reserve. • Ovarian tissue cryopreservation will not be an option as long as the risk of reseeding cancer cells is not fully eliminated. 5. Future Directions Advancements in molecular biology and genetics may shed light on the underlying mechanisms of ovarian cancer development and its potential association with fertility treatments. The artificial ovary and in vitro maturation of oocytes is a very attractive option in these patients, but further milestones have to be achieved

P-435 Superiority of modified natural cycle vs hormonal replacement therapy in non-menopausal egg recipients of advanced maternal age: clinical outcomes from 1273 single blastocyst transfer cycles

Abstract Study question Is the modified natural cycle (mNC) better than hormonal replacement therapy (HRT) for endometrial preparation in non-menopausal egg recipients of advanced maternal age? Summary answer In women above 40 years, mNC shows better reproductive and obstetrical outcomes compared to hormonal replacement therapy, especially in the subgroup 45-50 years old. What is known already There is extensive evidence showing the superiority of mNC over HRT in terms of live birth rates, miscarriages, and even obstetric complications. Apparently, the presence of the corpus luteum plays a major role in endometrial receptivity and embryo implantation, probably allowing for better placentation. Nevertheless, there is a general belief that the ovulatory cycle of older women is not the best choice for endometrial preparation, although paradoxically they are the group of patients who could benefit most from the reduction of obstetric complications. An increase in cancellation rates for mNC is claimed, without consistent data available. Study design, size, duration Retrospective single-centre comparative clinical study, including 1273 endometrial preparation cycles for frozen single-blastocyst transfer between January 2020 and December 2022: 892 (70,2%) on HRT protocol and 381 (29,8%) on mNC protocol. The two groups were homogeneous for donor’s age (25,7 years HRT vs 25,3 years mNC), recipient’s age (42,2 years HRT vs 42,1 years mNC), severe male factor (6% HRT vs 5% mNC), and the need for a sperm donor (28% HRT vs 26% mNC). Participants/materials, setting, methods Among 1273 started non-menopausal recipient’s cycles, we compared cancellation rates between HRT and mNC due to either medical reasons (inadequate endometrium, bleeding, premature ovulation) or other issues (no embryo survival, COVID-19, etc). We studied the outcomes of the 1096 elective frozen single-blastocyst transfers performed, comparing HRT and mNC cycles for: pregnancy, clinical pregnancy, miscarriage, live birth and <35weeks preterm birth rates. We stratified the results by age and used Chi-square test to compare groups (p < 0,05). Main results and the role of chance The overall cancellation rate was 13.9%. No significant differences in cancellation for medical reasons were found between HRT (7%) and mNC (6.8%), p = 0.93. When we analyse results stratified by age, patients aged 39 or less (270 cycles: HRT 75.9%, mNC 24.1%) showed no statistically significant differences in pregnancy (58% vs 64.6%, p = 0.35), clinical pregnancy (50.7% vs 56.9%, p = 0.34), miscarriage (18.3% vs 18.9%, p = 0.93), and live birth rates (41.5% vs 46.2%, p = 0.5). In the 40-44 age group (494 cycles: HRT 64.2%, mNC 35.8%), no statistically significant differences were found between HRT and mNC in pregnancy (58.2% vs 61.5%, p = 0.47), clinical pregnancy (50.8% vs 51.1%, p = 0.96), and live birth rates (40.4% vs 45.8%, p = 0.25). The HRT group had a significantly higher miscarriage rate (21%) compared to mNC (10%), p = 0.03. For patients aged 45-50 years (332 cycles: HRT 72%, mNC 28%), no statistically significant differences were observed in pregnancy (56.5% vs 62.4%, p = 0.33) and miscarriage rates (24.3% vs 15.1%, p = 0.18). Clinical pregnancy (44.8% Vs 57%, p = 0.04) and live birth rates (33.9% vs 48.4%, p = 0.01) were significantly higher in the mNC group compared to HRT. No significant differences were found between HRT and mNC in preterm birth rates <35 weeks (3.6% vs 4.6%, p = 0.75). Limitations, reasons for caution This study is a single-centre retrospective comparative trial. Our homogeneity study included several confounding variables, however other bias such as severe uterine factor, embryo quality or repeated implantation failure cases were not taken into account. Wider implications of the findings Modified natural cycle should be encouraged as the first option for endometrial preparation in non-menopausal egg recipients of advanced maternal age, having shown superiority over hormonal replacement therapy in patients aged 45-50 years. Moreover, modified natural cycles are more patient friendly and cost-effective, with no increase in the cancellation rates. Trial registration number not applicable

P-572 Circadian serum progesterone variations on the day of frozen embryo transfer in a modified natural cycle protocol

Abstract Study question Does a circadian variation of serum progesterone (P) on the frozen embryo transfer (FET) day in a modified natural cycle (mNC) exist? Summary answer A statistically significant diurnal variation of serum P on the day of a FET in a mNC protocol exists. What is known already In recent years, the proportion of FET cycles has increased dramatically. To further optimize pregnancy outcomes after FET, recent studies have focused on serum luteal P levels in both natural and artificially prepared FET cycles. Despite the different cut-off values proposed to define low serum P in the natural cycle, it is generally accepted that lower serum P values (<10ng/ml) around the day of FET are associated with negative reproductive outcomes. However, a single serum P measurement on the day of FET is not reliable given that P levels are prone to diurnal fluctuations and are impacted by patients’ characteristics. Study design, size, duration A prospective cohort study was conducted in a single fertility center including 22 patients performing a single blastocyst mNC-FET from August 2022 to August 2023.Serum P levels were measured on the day of transfer at 08:00h,12:00h,16:00h and 20:00h.Differences between P levels were compared using the Wilcoxon signed-rank test.The sample size was calculated to detect a difference of 15% between the first and last P measurements with a 5% false-positive rate and a 95% confidence interval. Participants/materials, setting, methods Patients with a normal BMI, between 18 and 40 years old, without uterine diseases were eligible. Patients utilizing donated oocytes were excluded. The mNC-FET protocol implied monitoring the normal ovarian cycle and triggering ovulation with an injection of 250 mcg of choriogonadotropin alfa when a pre-ovulatory follicle (16-20 mm diameter)was visualized. The blastocyst was transferred seven days later. The patients were not supplemented with exogenous P at any moment before the day of the FET. Main results and the role of chance The mean age and BMI of the study population were 33.6 ± 3.8 years and 22.7 ± 1.8 kg/m2, respectively. Mean P values at 08:00h,12:00h,16:00h, and 20:00h were 14.6 ± 4.5ng/ml, 14.7 ± 4.1ng/ml, 12.9 ± 3.5ng/ml, and 14.6 ± 4.3ng/ml, respectively. The mean P levels at 16:00h were statistically significantly lower compared to all other time points (p < 0.05:p= 0.007 between P at 8:00h and 16:00h;p = 0.003 between P at 12:00h and 16:00h;p=0.007 between P at 16:00h and 20:00h). Absence of a statistically significant fluctuation was observed between P values at the other time points (p = 0.88 between P at 8:00h and 12:00h;p=0.96 between P at 8:00h and 20:00h;p=0.83 between P at 12:00h and 20:00h). This study confirms the existence of an intra-day variation of serum P on the day of mNC-FET, with lower values at 16:00h. This highlights the importance of standardizing P measurement on the day of FET; we propose this should always be assessed in the morning to be more reliable and to allow the time to prescribe additional exogenous progesterone if lower P values (<10ng/ml) are detected. This standardization would allow fertility clinics around the world to compare their results and develop internationally recognized treatment protocols. Limitations, reasons for caution The study’s main limitation include the small sample size that may cause a bias when results are extrapolated to a larger subfertile population undergoing mNC-FET. Ideally, larger prospective trials including a more heterogeneous patient population would be necessary to validate our findings. Wider implications of the findings This study demonstrates the existence of a diurnal fluctuation of serum P on the mNC-FET day highlighting the importance of a standardized time point for its measurement.This is important when clinical actions, like additional exogenous P supplementation, are considered when encountering P values lower than 10ng/ml on the FET day. Trial registration number NCT05511272