GnRH Agonist Research Articles

P-306 GnRH agonists exert a positive influence on regulatory immune cells in the endometrium of women with adenomyosis

Abstract Study question How does treatment with GnRH-agonist (GnRH-a) prior to frozen embryo transfer (FET) in women with adenomyosis affect immune cell populations in endometrium and peripheral blood? Summary answer GnRH-a induces a decrease in monocytes and an increase in CD4+T-cells in peripheral blood and a decrease classical monocytes and T-regulatory cells in the endometrium What is known already Adenomyosis is associated with lower implantation and higher miscarriage rates. Observational studies have reported improved pregnancy outcomes in women with adenomyosis after assisted reproductive technologies (ART) and pre-treatment with GnRH-a prior to FET. However, the specific mechanisms of GnRHa action beyond central hormonal suppression remain unclear, but may be mediated through local and/or systemic immunomodulation. Study design, size, duration Prospective cohort study including infertile women with adenomyosis and GnRH-a treatment ≥3 months prior to FET. Pre- and post-treatment analysis of blood and endometrium samples were compared. Recruitment is ongoing with n = 30 women included thus far, 16 of whom have completed the study, while the remaining are still undergoing GnRH-a therapy. Participants/materials, setting, methods Adenomyosis was diagnosed sonographically if ≥ 2 criteria published by the MUSA group were met. Peripheral blood and endometrial samples were obtained before and after treatment with GnRH-a. Plasma cells and uterine Natural Killer (uNK) cells in endometrial biopsies were quantified with immunhistochemistry (IHC), and leukocyte populations in all samples were analysed using flow cytometry (FC). Pre- and post-treatment levels of immune cells and percentage of leukocyte populations were compared using Wilcoxon rank-sum tests (p < 0.05 significant) Main results and the role of chance Interim analysis of immune cell populations in peripheral blood and endometrium of the 16 women who already completed the study was performed. At baseline, IHC showed elevated plasma cell concentrations indicating chronic endometritis in 3/30 patients (10%), while uNK cells were elevated (>300/mm2) in 13/30 patients (43.3%). FC analysis of peripheral blood showed a significant decrease in percentage of monocytes (p = 0.01) and increase in percentage of T-cells (p = 0.03), specifically concentration of CD4+T-cells (p = 0.03), after treatment with GnRH-a as compared to pre-treatment levels. In the endometrium, following GnRH-a therapy, we observed a decrease in both the percentage of classical monocytes (p = 0.03) and T-regulatory cells (p = 0.03). All 16 participants who completed the study already underwent FET, resulting in ten pregnancies (62.5%), although four resulted in miscarriage, while the outcome of the remaining pregnancies is still pending. Limitations, reasons for caution These are preliminary results whose generalizability needs to be confirmed in a larger study population. No correction for multiple comparisons was performed and significant findings have to be interpreted with caution. Wider implications of the findings Elevated uNK on IHC cells seen at baseline may be associated with implantation failure, miscarriage. CD4+ and DN T-cells are important mediators of reproductive immune tolerance. In women with adenomyosis, GnRH-a may have a positive impact on these regulatory immune cells in peripheral blood as well as in the endometrium. Trial registration number Not applicable

P-639 Are GnRH-agonists (GnRH-a) safer and more effective ovulation triggers than human chorionic gonadotrophin (hCG)? A retrospective analysis of frozen embryo replacement cycle (FERC) outcomes

Abstract Study question Are GnRH-agonists (GnRH-a) safer and more effective ovulation triggers than human chorionic gonadotrophin (hCG)? A retrospective analysis of frozen embryo replacement cycle (FERC) outcomes Summary answer GnRH-a trigger reduces the incidence and severity of ovarian hyperstimulation syndrome (OHSS) leading to significantly improved clinical outcomes when compared to hCG trigger for FERCs. What is known already Ovulation induction plays a crucial role in the success and safety of ART cycles. hCG is extensively used as an alternative to LH to trigger ovulation. However, high levels of sustained hCG exposure increases the risk of OHSS, a potentially life-threatening complication of ART. To eliminate the risk and incidence of OHSS, GnRH-a can be used to trigger ovulation. Although there are concerns regarding clinical outcomes with fresh transfers following GnRH-a trigger, it elicits a more physiological response compared to hCG. This may lead to improved embryo quality, utilisation, and better clinical outcomes following a freeze-all strategy, reducing patients’ time-to-pregnancy. Study design, size, duration This was a retrospective data analysis of FERC outcomes following fresh IVF or ICSI cycles, involving ovulation induction using either hCG or GnRH-a as a final trigger. The evaluation included results from cycles spanning an eight-year period, from January 2012 to December 2019 at Hammersmith Hospital London. A total of 160 cycles were included in the study, with 76 in the hCG trigger group and 84 in the GnRH-a trigger group. Participants/materials, setting, methods Strict inclusion criteria were employed to render the study groups as comparable as possible and to minimise the effect of independent variables, such as oocyte and sperm factors, on oocyte or embryo developmental competence. Inclusion criteria: women ≤37 years old at the start of treatment, GnRH antagonist stimulation, blastocyst vitrification-warming and transfers only. Statistical significance was calculated using independent t-test and Fisher’s Chi-square exact test. Main results and the role of chance The mean age (±SD) of patients at the time of oocyte retrieval was comparable across groups. The average number of oocytes collected were significantly higher in the GnRH-a group compared to hCG (28.31 vs. 18.07, respectively, P < 0.001). Embryological data (maturation, fertilisation, blastocyst formation, blastocyst utilisation and good quality blastocyst formation rates) were comparable across both groups. OHSS rate was significantly lower in the GnRH-a group (17% vs. 50%. P < 0.0001). The following clinical data were significantly higher (P < 0.05) in the GnRH-a group compared to hCG: implantation rate (56% vs. 36%), clinical pregnancy rate (56% vs. 36%) and live birth rate (42% vs. 27%). Limitations, reasons for caution The biggest limitation of this study is its retrospective nature and the application of various inclusion-exclusion criteria that have resulted in relatively small sample sizes. Additionally, numerous other confounders, e.g. patient body mass index, cause/duration of infertility and stimulation duration, have not been considered in this study. Wider implications of the findings The findings of this study are promising and demonstrate a great potential for benefit in the use of GnRH-a trigger with a freeze-all strategy to minimise the risk of OHSS, diminishing the associated patient morbidity and mortality, reducing healthcare costs, improving clinical outcomes, and reducing the overall time-to-pregnancy for patients. Trial registration number not applicable

The effect of gonadotropin-releasing hormone agonist downregulation in conjunction with hormone replacement therapy on endometrial preparation in patients for frozen-thawed embryo transfer.

To investigate the effects of combining gonadotropin-releasing hormone agonist (GnRHa) downregulation with hormone replacement therapy (HRT, GnRHa-HRT) on the clinical outcomes of patients undergoing frozen-thawed embryo transfer (FET). In this retrospective study, we included patients who had FET between January 2018 and December 2022. They were categorized into HRT and GnRHa-HRT groups based on the endometrial preparation protocol. The study compared the clinical outcomes of patients in two groups. Possible factors affecting clinical outcomes were analyzed using univariate analysis. To analyze the impact of two endometrial preparation methods on clinical outcomes, multifactorial logistic regression was performed. The rates of clinical pregnancy (47.31% vs. 59.60%), embryo implantation (37.58% vs. 49.65%), biochemical pregnancy (52.36% vs. 64.31%), and early abortion (7.07% vs. 10.77%) were statistically different between the two groups (p < 0.05). Analysis using multifactorial logistic regression showed that there was a 1.65-fold increase in clinical pregnancy rates (OR = 1.65, 95% CI: 1.29-2.12, p < 0.001) and a 1.55-fold increase in embryo implantation rates (OR = 1.55, 95% CI: 1.27-1.90, p < 0.001) in the GnRHa-HRT group when compared to the HRT group. For blastocyst transfer, the clinical pregnancy and implantation rates of the GnRHa-HRT group were significantly higher than those of the HRT group (OR = 1.75, 95% CI: 1.30-2.37, p < 0.001; OR = 1.73, 95% CI: 1.35-2.21, p < 0.001). In FET cycles, leuprorelin (as a GnRHa) downregulation combined with HRT may improve the clinical outcome of patients compared to the HRT cycle, especially for the clinical pregnancy and embryo implantation rates of patients with blastocyst transfer.

Co-administration of GnRH-agonist and hCG (double trigger) for final oocyte maturation increases the number of top-quality embryos in patients undergoing IVF/ICSI cycles

BackgroundThe utilization of a double trigger, involving the co-administration of gonadotropin-releasing hormone agonist (GnRH-a) and human chorionic gonadotropin (hCG) for final oocyte maturation, is emerging as a novel approach in gonadotropin-releasing hormone antagonist (GnRH-ant) protocols during controlled ovarian hyperstimulation (COH). This protocol involves administering GnRH-a and hCG 40 and 34 h prior to ovum pick-up (OPU), respectively. This treatment modality has been implemented in patients with low/poor oocytes yield. This study aimed to determine whether the double trigger could improve the number of top-quality embryos (TQEs) in patients with fewer than three TQEs.MethodsThe stimulation characteristics of 35 in vitro fertilization (IVF) cycles were analyzed. These cycles were triggered by the combination of hCG and GnRHa (double trigger cycles) and compared to the same patients’ previous IVF attempt, which utilized the hCG trigger (hCG trigger control cycles). The analysis involved cases who were admitted to our reproductive center between January 2018 and December 2022. In the hCG trigger control cycles, all 35 patients had fewer than three TQEs.ResultsPatients who received the double trigger cycles yielded a significantly higher number of 2PN cleavage embryos (3.54 ± 3.37 vs. 2.11 ± 2.15, P = 0.025), TQEs ( 2.23 ± 2.05 vs. 0.89 ± 0.99, P < 0.001), and a simultaneously higher proportion of the number of cleavage stage embryos (53.87% ± 31.38% vs. 39.80% ± 29.60%, P = 0.043), 2PN cleavage stage embryos (43.89% ± 33.01% vs. 27.22% ± 27.13%, P = 0.014), and TQEs (27.05% ± 26.26% vs. 14.19% ± 19.76%, P = 0.019) to the number of oocytes retrieved compared with the hCG trigger control cycles, respectively. The double trigger cycles achieved higher rates of cumulative clinical pregnancy (20.00% vs. 2.86%, P = 0.031), cumulative persistent pregnancy (14.29% vs. 0%, P < 0.001), and cumulative live birth (14.29% vs. 0%, P < 0.001) per stimulation cycle compared with the hCG trigger control cycles.ConclusionCo-administration of GnRH-agonist and hCG for final oocyte maturation, 40 and 34 h prior to OPU, respectively (double trigger) may be suggested as a valuable new regimen for treating patients with low TQE yield in previous hCG trigger IVF/intracytoplasmic sperm injection (ICSI) cycles.

P-311 Impact of adenomyosis on reproductive outcomes applying the revised Morphological Uterus Sonographic Assessment criteria in fresh donor oocyte recipients pretreated with GnRH agonist

Abstract Study question Could the diagnosis of adenomyosis (AD) impact reproductive outcomes when applying the revised Morphological Uterus Sonographic Assessment (MUSA) criteria in fresh donor oocyte cycles? Summary answer Adenomyosis diagnosis following the revised MUSA criteria in recipients did not have adversely affect reproductive outcomes in fresh donor oocyte recipients pretreated with GnRH agonist What is known already Prior metanalysis on IVF outcomes in patients with adenomyosis suggested lower clinical pregnancy and live birth rates, and increased miscarriage rates. Some studies suggest improved pregnancy rates with ultra-long GnRH agonist pretreatment. Most studies focused on autologous embryo transfer without euploidy confirmation, and diagnostic criteria lacked consensus, in 2021 MUSA redefined criteria distinguishing direct and indirect features with different implications. Study design, size, duration A retrospective cohort study included all fresh oocyte donation cycles from January 2014 to September 2023, evaluating adenomyosis impact on implantation rate, clinical pregnancy rate, miscarriage rate, ectopic pregnancy rate. The study analyzed 252 cycles without a formal sample size calculation due to its retrospective nature. Participants/materials, setting, methods The study included 252 first fresh oocyte reception cycle with a fresh embryo transfer. Severe male factor cases were excluded. A transvaginal ultrasound (TUS) screening for adenomyosis criteria was performed, diagnosis required at least two criteria, with one being direct. Endometrial preparation involved one dose of 3,75mg triptorelin acetate intramuscularly injected in mid luteal phase, to facilitate the synchronization with donor and estradiol patches. Main results and the role of chance Adenomyosis was diagnosed in 10,7% (AD), endometriosis (END) was present in 21,8 % and 26,6% of patients presented both diagnoses. Endometriosis patients received more pre-treatment (oral contraceptive or 2-3 long-agonist doses) than those without (40,7% AD, 43,6% END vs 17,3% non-AD/END). Comparing patients with and without adenomyosis, no statistical differences were found in embryo transfer results between groups: clinical pregnancy rate (63% vs 56,9%), miscarriage rate (23,5% vs 14,1%), ectopic pregnancy rate (11,8% vs 4,7%) and live birth rate (40,7% vs 45,8%). No differences in gestational outcomes were observed in terms of the number of adenomyosis criteria present, the number of direct criteria, the type of criteria, or when differentiating between focal and diffuse adenomyosis. Similarly, there were no differences when comparing patients with both diagnoses to those with isolated adenomyosis. The most prevalent adenomyosis features reported were hyperechogenic islands (direct criteria), followed by an irregular junctional zone and asymmetrical wall thickening (indirect criteria). Finally, no differences were found in perinatal outcomes or complications during the pregnancy follow-up between groups. Limitations, reasons for caution Although this is the largest serie evaluating adenomyosisto the low adenomyosis prevalence in our population, these results should be confirmed in larger series. In our center all adenomyosis/endometriosis symptomatic patients are under medical treatment before assisted reproduction techniques, that may modify adenomyosis criteria over time and probably pregnancy outcomes. Wider implications of the findings This is the first study to characterize adenomyosis using the revised MUSA definitions in an oocyte donation programme. Applying these criteria and preparing endometrium with GnRH analog pretreatment and treating medically symptomatic patients before ART, adenomyosis did not adversely affect reproductive outcomes. Trial registration number Not applicable

P-286 Comparative study of frozen-thawed embryo transfer with modified natural cycle versus HRT cycle in previously cancelled true natural cycle patients

Abstract Study question Is there any difference in outcome of frozen embryo transfer(FET) between hormone replacement therapy(HRT) and modified natural cycle(MNC) in previously cancelled true natural cycle patients Summary answer In patients with previous history of cancelled true natural cycle, MNC results in higher clinical pregnancy rates after FET, when compared to HRT cycle What is known already Preparation of endometrium lays down the foundation for conception and subsequent successful pregnancy.There has been a plethora of endometrial preparation protocols described in the literature. The established protocols are true natural cycle,MNC with or without luteal phase support(LPS) and HRT cycle with or without gonadotrophin releasing hormone agonist(GnRha) suppression. Nevertheless,there is no consensus on protocol which may provide the best outcome in patients who have had cancelled true natural cycle.In such situations,HRT cycle may be considered as an easy option as the cancellation rate is low.However,HRT treatment is known for higher early pregnancy and obstetric complications,compared to MNC Study design, size, duration Prospective observational study,where 155 patients undergoing FET who had minimum one true natural cycle cancellation were recruited.They were divided into group A undergoing HRT cycle(n = 77) and group B for MNC cycle(n = 78).The study was conducted in a fertility unit over six months from June-November 2023.Primary outcome measures were serum betaHCG estimation and ultrasonographic documentation of intrauterine pregnancy.Results were analysed using statistical software SPSS version25 and p value of less than 0.05 was considered statistically significant Participants/materials, setting, methods HRT patients received injectable GnRha 3.75 mg on day21 of previous cycle.Oral estradiol valerate 6mg daily started on day2 of menses. When ET was minimum 7mm, luteal phase support(LPS) was started with daily oral and vaginal progesterone(30mg and 600mcg respectively),followed by FET. MNC patients received Letrozole 5mg daily from day 2-6 of menstruation.rhCG 250mcg was given subcutaneously,when ET was at least 7mm,dominant follicle 16-18mm and progesterone(P4) less than 1ng/ml.LPS(vaginal progesterone600mcg) was started 36hours after rHCG,followed by FET Main results and the role of chance Mean ET in MNC group was 8.92mm ± SD1.38, which was higher than HRT group (8.31 mm ± SD0.89). This difference was statistically significant with a p value of 0.014.Serum beta HCG estimation was done 2weeks after FET. In HRT group beta HCG was positive in 41 out of 77(53.25%) and in MNC group positivity was higher being 48 out of 78(61.54%). However, this difference was not statistically significant. Transvaginal ultrasonography(TVS) was done to confirm intrauterine pregnancy 2weeks after beta HCG assay. Clinical pregnancy rate(CPR) was higher in MNC group with 32 out of 78(41.03%),compared to 18 out of 77(23.38%) in HRT group. This difference is statistically significant with p value of 0.019 Limitations, reasons for caution Relatively small population in this study may be the reason for caution to interpret the statistical data. Study with higher numbers may bring about more robust conclusions Wider implications of the findings Patients with failed true natural cycles may be considered for modified natural cycle(MNC) stimulation for FET, without attempt of another true natural cycle 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 &amp;lt; 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 &amp;lt; 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 &amp;lt; 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

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.

O-219 Explainable artificial intelligence (XAI) to determine the follicle sizes on trigger day that maximize mature oocyte yield

Abstract Study question Which follicle sizes on trigger day (TD) are key to obtaining mature oocytes, embryos, and blastocysts, thereby enhancing live birth rates? Summary answer Follicles sized 13-18mm are most likely to yield mature oocytes. Live birth rate (LBR) was increased with a greater proportion of follicles in this range. What is known already At the time of oocyte retrieval, follicles that are either too small or too large are less likely to yield mature oocytes. However, there is only limited data examining which follicle sizes on TD administration are optimally sized to yield mature oocytes, nor any data examining whether live birth rates are impacted. Explainable artificial intelligence (XAI) offers a valuable opportunity to leverage clinical data to determine the range of follicle sizes that are most likely to yield mature oocytes and lead to improved downstream outcomes. Study design, size, duration A retrospective study incorporating 19,082 patients undergoing their first IVF/ICSI cycle (2005-2023) across 11 European clinics. Follicle sizes on TD were related to oocyte maturity (14,140 patients), fertilization (17,822 patients), high-quality blastocyst development (17,488 patients), and pregnancy outcomes (12,672 patients). Secondary analyses included stratification by age (&amp;gt;35 years: 4,717 patients; ≤35 years: 5,707), and suppressant protocol (GnRH agonist: n = 5,420 patients; GnRH antagonist: n = 3,982). Participants/materials, setting, methods An ensemble-based XAI model, developed through ‘internal-external validation’, was trained, Bayesian optimized, and independently iteratively tested on hold-out clinic datasets. The model determined follicle sizes contributing most to successful laboratory outcomes by harnessing permutation importance and ‘SHAP’ values. Model performance was evaluated and optimized for mean absolute error (MAE). The top 50% contiguous cohort of influential follicle sizes on TD were identified, and further validated through analysis of follicle sizes on preceding days. Main results and the role of chance XAI analysis revealed that follicles sized 13-18mm on TD were most influential in yielding mature oocytes, especially those sized 15-18mm (MAE: 3.60 ±0.35). Predictive follicle sizes from scans 1-2 days preceding TD administration were consistent with expected mean follicle growth rates. For high-quality blastocysts, follicles sized 14-20mm were contributory, narrowing to 15-18mm in the subset of patients where oocytes had been confirmed to be mature. In hCG-triggered cycles, follicles sized 12-19mm were most likely to yield mature oocytes in GnRH antagonist cycles, whereas follicles sized 14-20mm were most contributory in GnRH agonist cycles. In patients ≤35 years, follicles 13-18mm were most contributory, whereas a wider range of follicles (11-20mm) were contributory in patients &amp;gt;35 years. In line with current practice, having three lead follicles ≥17mm on TD was associated with a median improvement in mature oocyte yield of 10% versus those that did not (p &amp;lt; 0.0001). By comparison, maximizing the proportion of follicles on TD within the optimal size range could better improve mature oocyte yield, for example, by 42% when at least 70% of follicles were sized 15-18mm (p &amp;lt; 0.0001). Likewise, LBR improved as the proportion of follicles sized 13-18mm was increased (&amp;lt;10%: 23.3%; 10-20%: 25.7%; 20-30%: 28.8%; 30-40%: 31.6%). Limitations, reasons for caution These data could help guide when to administer the trigger to optimize clinical outcomes, however prospective assessment of different TD strategies based on the proportion of follicles within the optimal follicle size ranges identified in comparison to current practice based on lead follicle size is required prior to clinical adoption. Wider implications of the findings These findings provide a data-driven approach to personalizing ovarian stimulation in IVF. The findings generated by applying an XAI model could assist clinicians in optimizing TD timing, potentially enhancing clinical outcomes by moving beyond the conventional focus on lead follicle size. Trial registration number not appicable

P-683 Progestins vs flexible GnRH antagonist for LH suppression during controlled ovarian stimulation in POSEIDON groups 3 and 4 patients: Analysis of effectiveness and cycle outcomes

Abstract Study question How do cycle outcomes differ between controlled ovarian stimulations using progestins vs flexible GnRH antagonists for LH suppression in women with diminished ovarian reserve (DOR)? Summary answer While progestin use is associated with significantly higher blastocyst rate than GnRH antagonists in POSEIDON group 4, the latter gives better results in group 3. What is known already Controlled ovarian stimulation (COS) in patients with DOR carries the additional risk of premature luteinizing hormone (LH) surge and ovulation.GnRH antagonists are popular for LH suppression in COS because of their convenient, quicker onset of action, flexibility to use GnRH agonist as a trigger and continue as double stimulation, allowing rapid pooling of embryos. Ease of oral administration, combined with cost-effectiveness and retention of all the benefits of GnRH antagonists makes progestins an attractive alternative to GnRH antagonists for COS in patients with DOR who often need multiple stimulation cycles to enable the pooling of embryos. Study design, size, duration An open-label, multicentric, randomized controlled study was conducted over 1 year from January 2023 to December 2023. 140 women aged 21- 42 years and with AMH &amp;lt;1.2 ng/dl were randomized into 2 groups in a 1:1 ratio, using either oral progestins or GnRH antagonists for LH suppression. The two groups were further comparative analyzed under POSEIDON 3 and 4 subgroups. Those with BMI &amp;gt;40kg/m2 and with partners having severely compromised semen parameters were excluded. Participants/materials, setting, methods In Group A (PPOS): Medroxyprogesterone acetate 10 mg orally was given daily with gonadotropins (hMG 300- 375 IU) from cycle day 2 until trigger. In Group B (Antagonist), patients had daily GnRH antagonist, cetrotide 0.25 mg, subcutaneous administration started when the dominant follicles reached 12-14 mm size during controlled ovarian stimulation. This was continued until the trigger. Following oocyte retrieval and ICSI, embryos were cultured until D5 and vitrified fortransfer in subsequent HRT cycles. Main results and the role of chance Patients in Group A, using PPOS, were noted to have significantly better fertilization rates than those in Group B, using flexible GnRH antagonists (0.82 + 0.2 vs 0.66 + 0.4, p-value &amp;lt;0.01). Though the number of top-quality embryos (TQE) frozen was not significantly different between groups A and B (p-value = 0.44), a significant difference in the outcome was noted when comparatively analyzed under the subgroups of POSEIDON groups 3 and 4. While patients in POSEIDON group 4 got significantly more top-quality embryos (TQE) when progestins were used for LH suppression (1 + 0.11 vs 0.77 + 0.41, p-value &amp;lt;0.01), those in POSEIDON group 3 got significantly more top-quality embryos when GnRH antagonist was used (0.94 vs 2, p-value &amp;lt;0.01). Patients in Group A and B were found to have no significant difference in the following outcomes: incidence of premature LH surge (4.3% vs 7.1%, p value= 0.71), number of days of stimulation (10.26 + 2.18 vs 10.26 +2.94, p value= 0.99), total gonadotropin dosage used (3448.64+ 1007.98 vs 3087.41 + 1260.56, p value=0.06), total number of oocytes retrieved (5.84 + 3.3 vs 4.9 + 3.4, p value=0.09) and total cycle cancellation rate (30.1% vs 35.7%, p value= 0.11). Limitations, reasons for caution The small sample size of the cases limits the current statistical power of the study. The results being encouraging need to be confirmed in a larger patient population and followed for a longer duration to enable calculation of implantation and clinical pregnancy rates for all patients. Wider implications of the findings Oral progestins are an effective and cheaper, patient-friendly alternative to injectable GnRH antagonists during COS in women with DOR. Considering the significantly higher TQEs formed, PPOS can be preferred in older, POSEIDON group 4 patients, whereas flexible GnRH antagonist protocol can be our choice in the younger, POSEIDON group 3. Trial registration number Not applicable

P-615 Can the use of progestin in egg donation cycles influence morphokinetic parameters of embryos when compared with GnRH antagonist during ovarian stimulation? A case-control study

Abstract Study question Are there differences in clinical and morphokinetic parameters of embryos obtained from fresh egg donation cycles using GnRH antagonist versus PPOS on same donor? Summary answer Lower number of oocytes retrieved and faster early morphokinetics parameters were observed in PPOS protocol. What is known already Controlled ovarian hyperstimulation (COH) is a crucial step in assisted reproduction treatments and the ideal protocol should be chosen according to the patient’s profile, based on literature results, intending to achieve high effectiveness. The use of PPOS in ovarian stimulation protocols is getting attention because of its safety, efficacy and proved to be patient friendly and an economical alternative to avoid premature LH surge. In the last years, morphokinetics parameters started to be considered in embryo classification and selection, as they correlate to embryo implantation potential. Here, morphokinetics parameters were compared from two different COH in donated oocyte cycles. Study design, size, duration Case-control study including cycles from 10 oocyte donors and 20 recipient patients, whose embryos formed with fresh oocytes were cultured in a time-lapse system (Embryoscope® Plus), in a single private IVF center between Jun/2020 and Oct/2022. Each donor were submitted to two cycles: first stimulation with standard GnRH antagonist (ant) short protocol (group A) and in a posterior cycle: a second stimulation with progesterone (PPOS protocol with dydrogesterone, group B). Participants/materials, setting, methods All donors used menotropin for COH (doses adjusted according to patient’s profile). Group A started GnRh ant with follicle above 14 mm. On group B, dydrogesterone 10 mg was started on the first day of COH and maintained until the day of ovulation trigger, which was performed with GnRH agonist. Clinical and morphokinetics parameters were compared. Paired t-test, t-test or Mann-Whitney were used properly, values of p &amp;lt; 0.05 were considered significant. Main results and the role of chance A total of 70 blastocysts were analyzed, 39 from group A and 31 from group B. The following morphokinetics parameters were annotated: time of PN fading (tPNf), time to two cells (t2), three cells (t3), four cells (t4), five cells (t5), eight cells (t8), time to morula (tM), time to blastulation (tB) and KIDScoreTM. Statistically significant differences were observed for tPNf: group a) 24,01 ± 3,28h versus b) 22,59 ± 2,48h, p = 0,0484, t2: a) 26,30 ± 3,24h versus b) 24,76 ± 2,27h, p = 0,0211; t3: a) 37,04 ± 4,44h versus b) 35,53 ± 2,93, p = 0,0347 and t4: a) 38,38 ± 5,15h versus b) 36,05 ± 3,32h, p = 0,0152. Clinical characteristics of the donors were also analyzed: age, body mass index (BMI), total gonadotropin dose, antral follicular count (AFC), follicle stimulating hormone (FSH), basal hormone levels, follicle count, oocyte pick-up (OPU), altered oocytes, number of germinal vesicles, metaphase I (MI) and metaphase II (MII) oocytes. Differences were observed only between two clinical aspects: patients’ age: a) 24,2 ± 3,6 versus b) 25,0 ± 3,3, p = 0,0031 and OPU: a) 23,3 ± 9,1 versus b) 18,6 ± 8,3, p = 0,004, however both variables does not seem to affect embryo formation potential. Limitations, reasons for caution The results should be interpreted with caution due to the limitations of evaluate a small dataset of donors, resulting in low number of embryos in each group of protocols for analysis. Wider implications of the findings In this case-control study, a lower number of oocytes retrieved and faster early morphokinetics times were observed in PPOS compared to antagonist protocol. The implications of these differences still need further data analyses to compare if these findings can change clinical outcomes. Trial registration number Not applicable.

P-663 Comparing clinical outcomes in PGT-A cycles using donated oocytes between progesterone and GnRH-antagonist protocols

Abstract Study question Does Progesterone Primed Ovarian Stimulation (PPOS) demonstrate comparable efficiency to the GnRH-antagonist protocol in terms of laboratory/reproductive outcomes in PGT-A cycles with donated oocytes? Summary answer PPOS demonstrates efficiency in PGT-A cycles with donated oocytes, comparable to the GnRH-antagonist protocol, providing cost-effectiveness and enhanced donor comfort. What is known already The demand for TRA cycles with donated oocytes steadily rises each year. This treatment instills high hopes for success. Ongoing advancements in donor stimulation protocols prioritize safety and comfort. The shift from LH agonist to antagonist suppresses LH peaks, and recently, PPOS has joined, offering a more comfortable, cost-effective, and equally safe alternative with fewer ultrasound checks, mitigating ovarian hyperstimulation syndrome. Study design, size, duration Retrospective assessment of an oocyte donor cohort undergoing ovarian stimulation: 182 cycles with the GnRH-antagonist protocol (Group 1: G1) and 120 with PPOS (Group 2: G2), conducted between July 2017 and June 2023. Ovarian stimulation involved 225 IU/d of FSHr or FSHu, triggering with a GnRH agonist, and subsequent biopsy of evolutionarily robust embryos after extended culture. Both fresh and vitrified oocytes, inseminated with either self or donor sperm, were included. Participants/materials, setting, methods We analyzed 1188 embryos (G1: 676; G2: 512). Trophoectoderm biopsies from D5/D6 blastocysts underwent NGS using the Illumina platform (VeriSeq Illumina®, San Diego, CA, USA). Comparison included total and MII oocyte numbers, fertilization rates, viable embryos, euploid/aneuploid embryos, mosaic embryos, and clinical outcomes: biochemical pregnancy (BPR), biochemical pregnancy loss (BPLR), clinical pregnancy (CPR), early pregnancy loss (EPLR), ongoing pregnancy (OPR), and live birth (LBR) rates. Statistical analyses were carried out using R statistical software (v.4.3.1). Main results and the role of chance The mean ages of donors (25.57±4.05) and recipients (41.82±4.06) were comparable in both groups. The male partner’s age differed (G1: 40.47±7.87; G2: 42.34±7.65) (p = 0.019). Results were adjusted for confounding factors, including recipient and donor ages, oocyte and seminal origin, and male factor variables. Ovarian stimulation duration (9.26 days), total gonadotropin dose (2015.64 IU), and oocyte origin (fresh G1: 69.8 %; G2: 62.5 %; vitrified G1: 30.2 %; G2: 37.5 %) showed equivalence. Statistical significance emerged in total oocytes retrieved (G1: 17.92±7.64; G2: 20.23±7.89) (p = 0.008), mean microinjected MII (G1: 10.25±1.79; G2: 10.07±1.36) (p = 0.040) and fertilization rate (G1: 73.98 %; G2: 79.44 %) (p = 0.001). The usable embryo rate was similar (G1: 54.78 %; G2: 54.47 %). Significant differences arose in mean biopsied embryos/cycle (G1: 3.71; G2: 4.27) (p = 0.016), but not for aneuploid embryos (G1: 29.71 %; G2: 29.49 %) (p = 0,998). Biochemical pregnancy rates were significant (G1: 48.8 %, G2: 60.4 %) (p = 0.022). Other clinical parameters showed no differences, with LBR at 35.5 % in G1 and 37.8 % in G2 (p = 0.752). Limitations, reasons for caution The study is retrospective, where we addressed potential biases by incorporating confounding variables. However, to confirm our initial findings, randomized prospective studies with an appropriate sample size are essential. Wider implications of the findings In egg donation cycles, PPOS shows optimal embryonic performance resulting in a live birth rate comparable to the GnRH antagonist protocol. Additionally, it offers cost-effectiveness and enhanced comfort for donors. Trial registration number Not applicable

O-074 Dual trigger is not superior to GnRH Agonist alone for final oocyte maturation in elective fertility preservation. A Randomized Controlled Trial

Abstract Study question Is Dual trigger for final oocyte maturation associated with a higher number of mature (MII) oocytes compared to GnRH-a trigger alone in elective fertility preservation? Summary answer Adding hCG to GnRH-a for triggering final oocyte maturation does not increase the number of MII oocytes in elective fertility preservation cycles. What is known already Triggering final oocyte maturation represents a key step in ovarian stimulation. In good prognosis patients undergoing oocyte cryopreservation, the current standard approach involves the administration of a single bolus of GnRH-agonist 36 hours before the pick-up. Previous studies have shown a higher number of MII oocytes when Dual Trigger (hCG+ GnRH-a) is performed, compared to recombinant human chorionic gonadotropin (rhCG) alone. Nevertheless, a notable gap exists in the literature, as no studies have investigated the potential additional benefit in final oocyte maturation when dual trigger is compared to GnRH-a alone. Study design, size, duration This is a randomized controlled superiority trial including elective oocyte cryopreservation cycles performed in a University Hospital. A total of 109 women were enrolled in this study between October 2021 to April 2023 with a 1:1 allocation. Eligible patients were ≤40 years old, with an antral follicular count (AFC)&amp;lt;20 and anti-Mullerian hormone (AMH)≤3ng/ml. Patients were randomized to final oocyte maturation triggering with Triptorelin 0,2mg or a dual trigger (Triptorelin 0.2 mg + 250 ug rhCG). Participants/materials, setting, methods Controlled ovarian stimulation was performed using 225-300IU/day of rFSH alfa or beta, or equivalent rFSH delta (15-20μg), tailored to ovarian reserve and BMI. LH surge was suppressed through a progestin-primed ovarian stimulation (PPOS) protocol, with oral administration of micronized progesterone (200mg daily) from the beginning of ovarian stimulation until the trigger day. The primary outcome was the number of MII oocytes. Comparisons are presented as estimated mean difference (EMD) and corresponding 90% confidence interval (CI). Main results and the role of chance Overall, 104 patients were analyzed, 51 in the Dual trigger group and 53 in the control arm (GnRH-a). We found no statistically significant differences in the number of retrieved oocytes comparing Dual Trigger group (8.71 ± 4.90) and GnRH-a group (9.51 ± 5.19). Similarly, the number of MII oocytes demonstrated no significant differences, with 6.86 ± 4.40 in the Dual Trigger group compared to 7.87±4.40 in the GnRH-a group (EMD -1.01 [90%CI: -2.44;0.43]). Exploring the hormonal profile there were no notable variations in estradiol levels (2064.60 ± 890.50 pg/ml vs. 2494.41 ± 1341.05 pg/ml), progesterone levels (7.78 ± 3.88 ng/ml vs. 8.94 ± 5.10 ng/ml), LH (56.28 ± 26.83 IU/L vs. 63.41 ± 32.50 IU/L), and FSH (31.14 ± 7.86 IU/L vs. 31.53 ± 9.89 IU/L) on the day following the trigger. Notably, neither group exhibited any case of Ovarian Hyperstimulation Syndrome (OHSS). Limitations, reasons for caution The sample size was calculated to detect differences on the number of MII oocytes. Therefore, results for secondary outcomes (number of oocytes retrieved and hormonal profile) should be interpreted with caution. Wider implications of the findings Adding hCG to GnRH-a for triggering final oocyte maturation does not confer any additional benefits in elective fertility preservation in term of MII oocytes compared to the administration of GnRH-a alone. Trial registration number NCT04992468

P-703 Is the time interval between triggering final oocyte maturation and oocyte retrieval associated with ART outcomes? A systematic review and meta-analysis

Abstract Study question Is the time interval between triggering final oocyte maturation and oocyte retrieval associated with assisted reproductive technology (ART) outcomes? Summary answer Limited evidence suggests that extending the time interval between triggering final oocyte maturation and oocyte retrieval from 33-36h to 37-41h does not affect ART outcomes. What is known already The time interval between final oocyte maturation and oocyte retrieval varies among IVF centres, although an interval of 33–36 h is the most widely adopted. The use of a prolonged time interval of 37-41h has been suggested to increase the number and competence of oocytes retrieved, their maturation, their ability to be fertilized, their capacity to produce usable embryos and the probability of pregnancy. Considering recently published data, a systematic review is warranted to provide clinicians with updated, evidence-based information regarding the optimal time interval between triggering final oocyte maturation and oocyte retrieval. Study design, size, duration A systematic review and meta-analysis was performed aiming to evaluate the effect of the time interval between triggering final oocyte maturation and oocyte retrieval on ART outcomes. For this purpose, a literature search was carried out until January 2024 in PubMed, MEDLINE and CENTRAL. The primary outcome measure was clinical pregnancy rate, while ovulation before oocyte retrieval, oocytes retrieved, maturation rate, fertilization rate, blastulation rate, implantation rate and miscarriage rate were secondary outcomes. Participants/materials, setting, methods Citation, demographic, methodological and clinical data were extracted from the studies by two independent reviewers. Quality was assessed using the RoB2 Tool by Cochrane. Statistical heterogeneity was assessed by I2. In dichotomous data, estimates were expressed as relative risk (RR) with 95% confidence intervals (CIs), using the fixed or random effects method. In continuous data, differences were pooled across resulting in a weighted mean difference (WMD) with 95% CI. Main results and the role of chance Six eligible RCTs (n = 1081) were identified, published between 1991-2023. In three trials, conventional insemination was used for fertilization, in two trials this was performed by intracytoplasmic sperm injection (ICSI), whereas in one trial either conventional insemination or ICSI were used. The time intervals between triggering final oocyte maturation and oocyte retrieval compared, varied between studies (34.5-36 vs 38.5-40h, 33 vs 41h, 34 vs 38h, 35 vs 37h, 34 vs 39h and 36 vs 38h). Patients were grouped in advance based on these time intervals (short interval group: 33-36h versus long interval group: 37-41h). Ovarian stimulation was performed with GnRH analogues (GnRH antagonists:1 GnRH agonists:5) and gonadotrophins (HMG:4 recombinant FSH:2, while triggering of final oocyte maturation was performed with hCG( recombinant hCG:1 urinary hCG:5). None of the studies was deemed as of low risk of bias. No statistically significant differences were observed between the short nd long interval groups regarding clinical pregnancy rate per randomized patient (RR: 0.83; 95%CI: 0.62-1.11; fixed effects model; heterogeneity: I2:36.4%; five studies, 827 patients). Furthermore, it was not feasible to pool any of the secondary outcome data. This was either because they were not reported, or due to the fact that they were reported inappropriately. Limitations, reasons for caution This meta-analysis included a limited number of RCTs, which were generally of low quality due to methodological limitations and of high risk of bias. Moreover, the total number of patients is still not large enough to draw solid conclusions. Wider implications of the findings Taking into account the limitations of the current meta-analysis, it appears that clinicians may elect a shorter (33–36 h) or a longer (37-41h) interval regarding the timing of oocyte retrieval following triggering final oocyte maturation, without affecting clinical pregnancy rate. Trial registration number PROSPERO: CRD42024501986

P-671 Modelling human follicle growth and development during ovarian stimulation: a physiological computational approach

Abstract Study question Can key elements of ovarian physiology be accurately modelled, thereby providing a tool to generate novel insights and guide development of new therapeutics? Summary answer A physiological computational model was developed to describe follicle growth and follicle size distributions observed in agonist and antagonist ovarian stimulation (OS) protocols. What is known already The outcome of OS remains unpredictable despite identification of several prognostic factors. The average first cycle pregnancy rate is 30-40% across fertility centres, highlighting the need for improved stimulation protocols. This is an active area of clinical research; however, clinical trials are costly, time-consuming, and frequently have outcomes that are unexpected or difficult to interpret. We integrated available physiological knowledge of human follicle growth and development and clinical trial data into a computational model to enable in silico simulations with the aim to optimise clinical trial design. Study design, size, duration Computational model building was performed using a mechanistic approach aimed at capturing well-understood physiology that is relevant in OS protocols. Model inputs included patient characteristics (such as anti-Müllerian hormone (AMH) level), OS regimen and pituitary downregulation with gonadotrophin releasing hormone (GnRH) agonist or antagonist. Key outputs of the model included follicle number and mean size, duration of stimulation and serum hormone concentrations (oestradiol, testosterone, inhibin B and androstenedione). Participants/materials, setting, methods Published physiological data on regulation of follicle development and hormone production informed model design. Following implementation of the model in the Python platform, data from two OS clinical trials were used to calibrate (partially censored) and test the model. The two trials provided data on the effects of the recombinant follicle stimulating hormone preparation follitropin delta over a range of fixed doses and compared the effects of follitropin delta in agonist and antagonist OS protocols. Main results and the role of chance The computational model describes the interplay between pituitary gonadotrophins ovarian steroid hormones and follicle growth and development. Processes spanning the cellular level (such as steroidogenesis and receptor dynamics in theca and granulosa cells), the ovaries (follicle number and size) and the organism (pharmacokinetics and hypothalamic-pituitary-ovarian axis) are included as a system of coupled differential equations. Approximately 70 compartments, 500+ parameters and 1700+ reactions constitute the model framework. Follicles are recruited in the model at variable times, starting from 7 days prior to the start of stimulation. Follicles are initialised with individual sensitivity to gonadotrophins and growth rates. The fate of each follicle (dominance or atresia) is governed by these properties, which determine whether the balance shifts towards proliferation or atresia under the influence of gonadotrophins. Model-simulated numbers of follicles, their average size and mean serum hormone concentrations match closely with observed values in the two clinical trials. For each of these variables, their dependence on time, the dose of follitropin delta, AMH level and downregulation protocol were described with good precision. The inter-patient variability in the simulated number of follicles and in serum hormone levels matched closely with the observed variability based on comparison of the interquartile range. Limitations, reasons for caution The computational model currently describes follicle development during treatment with follitropin delta. We envision extending the model to encompass other treatment outcomes and additional preparations of exogenous gonadotrophins. While the model incorporates our current understanding of mechanisms important for follicle development, ongoing research in the field will likely drive improvements. Wider implications of the findings The computational model is hypothesis-generating and can improve the design of future clinical trials through in silico trial simulation. For instance, the effects of changing subject inclusion/exclusion criteria or of novel dosing regimens can be investigated. Trial registration number NCT01426386, NCT03809429

P-392 Luteal phase support for women trying to conceive by intrauterine insemination or sexual intercourse

Abstract Study question Is luteal phase support (LPS) necessary for intrauterine insemination or sexual intercourse? Summary answer Vaginal progesterone supplementation during luteal phase may increase live birth (LBR)/ongoing pregnancy rate (OPR), however, its effect on miscarriage per pregnancy (MPP) is uncertain. What is known already Ovulation induction may impact endometrial receptivity due to insufficient progesterone secretion. Low progesterone is associated with poor pregnancy outcomes. Study design, size, duration Systematic reviews and meta-analysis were conducted. We searched the Cochrane Gynaecology and Fertility Group Specialised Register, CENTRAL, MEDLINE, Embase, PsycINFO, LILACS, trial registries for ongoing trials, and reference lists of articles (from inception to 25 August 2021). Participants/materials, setting, methods Randomised controlled trials (RCTs) of LPS using progestogen, human chorionic gonadotropin (hCG), or gonadotropin-releasing hormone (GnRH) agonist supplementation in IUI or natural cycle. We used the standard methodological procedures expected by Cochrane. Main results and the role of chance We included 25 RCTs (5111 participants). Progesterone supplementation versus placebo or no treatment Vaginal progesterone does not significantly increase the LBR/ OPR (RR 1.10, 95% confidence interval (CI) 0.81 to 1.48; 7 RCTs; 1792 participants;) or decrease MPP (RR 0.70, 95% CI 0.40 to 1.25; 5 RCTs; 261 participants). Subgroup analysis revealed that progesterone may not increase LBR/OPR in women with gonadotropin stimulation (RR 1.24, 95% CI 0.80 to 1.92; 4 RCTs; 1054 participants) and oral stimulation (clomiphene citrate or letrozole) (RR 0.97, 95% CI 0.58 to 1.64; 2 RCTs; 485 participants). In addition, progesterone may not reduce MPP regardless of stimulation protocol (RR 0.68, 95% CI 0.24 to 1.91; 2 RCTs; 102 participants, with gonadotropin; RR 0.67, 95% CI 0.30 to 1.50; 2 RCTs; 123 participants, with gonadotropin plus oral stimulation; and RR 0.53, 95% CI 0.25 to 1.14; 2 RCTs; 119 participants, with oral stimulation). Different routes of progesterone administration versus vaginal route There is no difference in terms of LBR, OPR, and MPP when comparing intramuscular (IM), oral, or subcutaneous progesterone to vaginal progesterone. Very low-certainty evidence suggests that intramuscular progesterone may lead to a substantial increase in adverse events, particularly pain at the site of injection. Limitations, reasons for caution Most studies were at unclear or high risk of bias. The main limitations of the evidence were poor reporting and imprecision. Wider implications of the findings Vaginal progesterone does not significantly increase in LBR/OPR or decrease miscarriage rate. In comparison to vaginal progesterone, there is insufficient data to evaluate whether progesterone supplementation via an alternative route has an impact on pregnancy outcomes. Trial registration number PROSPERO2017 CRD42017055106

P-369 DuoStim could be a proper option for women seeking fertility preservation for non-medical reasons

Abstract Study question Is Duostim a suitable option for women who wish to preserve fertility for social reasons? Summary answer Providing the option of DuoStim is an efficient way to expand the cohort of vitrified oocytes in women seeking fertility preservation for non-medical reasons. What is known already A growing number of reproductive-age women are choosing to postpone motherhood, giving rise to the concept of reproductive autonomy. Numerous strategies aim to refine ovarian stimulation protocols. DuoStim, entailing dual ovarian stimulations and retrievals within one menstrual cycle, proves advantageous for those with diminished ovarian reserve or facing cancer. To our knowledge, this is the first study offering DuoStim for social preservation. Study design, size, duration Retrospective controlled case-control study conducted with paired follicular phase stimulation (FPS) and luteal phase stimulation (LPS) derived cohorts of oocytes collected in the same ovarian cycle (DuoStim). The study included 160 patients aged 36.85 ± 3.3 years old, who underwent DuoStim for social egg freezing from October 2018 to September 2023. The primary outcome was the number of MII oocytes retrieved per cycle and secondary outcomes included stimulation duration and gonadotropin dose. Participants/materials, setting, methods FPS and LPS were performed using the same daily dose of recombinant gonadotropins in an antagonist protocol. Oocyte retrieval was performed 36 hours after triggering with gonadotropin-releasing hormone agonist triptorelin acetate (0,2 mg) after the FPS. Luteal phase stimulation protocol began on the 5th day after ovarian puncture using dual trigger, followed by a second oocyte retrieval. Mature oocytes were vitrified 2 hours later following the Kitazato® protocol. Main results and the role of chance Stimulation duration and gonadotropin dose were lower during Follicular Phase Stimulation (FPS) vs. Luteal Phase Stimulation (LPS) (10.8 ± 1.5 days vs. 13.0 ± 2.3, P &amp;lt; 0.05 and 2,487.9 ± 580.8 vs. 3,264.0 ± 942.7, P &amp;lt; 0.05). The number of retrieved oocytes was comparable between the two groups (4.78 ± 3.0 vs. 5.32 ± 3.7; P = 0.15). The mean number of MII oocytes acquired in the LPS group exceeded that in the FPS group (4.16 ± 3.0 vs. 3.58 ± 2.3; P = 0.054), indicating a tendency towards more MII oocytes in the LPS group without achieving statistical significance. A total of 110 patients (69.29%) obtained the same or a greater number of MII during the LPS compared to the FPS. Limitations, reasons for caution Although DuoStim is acknowledged as an option to obtain a greater number of eggs in certain situations, the evidence supporting its utility in social fertility preservation is still limited. It is crucial to recognize the inherent biases in observational retrospective studies. Wider implications of the findings DuoStim could be an advantage for women who live abroad or those who dispose of short periods of time for oocyte vitrification, also potentially reducing the drop-out rate. Trial registration number not applicable

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 &amp;lt;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 &amp;gt; 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 &amp;lt;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 &amp;lt; 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-695 Optimizing oocyte donor stimulation: A revelation from 2,666 cases emphasizing the sole efficacy of exogenous FSH

Abstract Study question Does the administration of human menopausal gonadotrophin in controlled ovarian stimulation improve clinical outcomes in the oocyte donation program? Summary answer The addition of hMG (human menopausal gonadotropin) reduces the number of retrieved oocytes without improving embryo development or clinical outcomes in oocyte donation program. What is known already In controlled ovarian stimulation for assisted reproduction treatments, follicle stimulating hormone(FSH) is essential, but the importance of LH supplementation from menopausal origin is controversial. It is a common practice to use hMG to provide the LH effect. The standard preparation contains FSH and LH effects in a 1:1 ratio.The FSH component would recruit ovarian follicles and stimulate their growth, while the LH component would facilitate their maturation. Our aim was to compare the outcomes of intracytoplasmic sperm injection (ICSI) treatments using a gonadotropin-releasing hormone GnRH) antagonist protocol with recombinant FSH(FSHr) alone and supplemented with hMG in the oocyte donation program. Study design, size, duration This is a retrospective cohort study of 2,666 patients enrolled in the oocyte donation program at a single center over four consecutive years. Donor stimulation commenced with daily FSHr injections. The FSHr group (n = 2,078) continued FSHr, while the FSHr+hMG group (n = 588) received hMG. Participants/materials, setting, methods Donors received GnRH agonist via i.m. injection until a mean diameter &amp;gt;18 mm in at least eight follicles. Transvaginal oocyte retrieval was scheduled 36h later, followed by ICSI for all retrieved oocytes. Embryos were cultured in time-lapse systems and evaluated using an artificial intelligence-based model (iDAScore v2). Recipients underwent hormone replacement therapy for endometrial preparation. Our comparative study examined oocytes retrieved, embryo score, implantation, and live birth outcomes in fresh and frozen embryo transfers (ETs). Main results and the role of chance The number of retrieved oocytes was higher in the FSHr group than in the FSHr+hMG group: 24.9±10.6 vs. 18.2±8.8 (p &amp;lt; 0.001). In addition, embryos from the FSHr+hMG group exhibited slower early development, with significantly lower division times to two, three, four and five cells in the FSHr group (p &amp;lt; 0.005). However, late parameters of embryo development showed no differences. Automatic scoring by the deep learning algorithm was identical for blastocysts in the FSHr (4.8±2.8) and FSHr+hMG groups (4.8±2.8); p = 1. Implantation rates showed no significant differences for fresh ET (FSHr: 58.6% vs. FSHr+hMG: 61.9%; n = 2,073; p = 1) or frozen ET (FSHr: 49.3% vs. FSHr+hMG: 46%; n = 2,687; p = 1). Similarly, there were no differences in live birth rates for fresh ET (FSHr: 45.6% vs. FSHr+hMG: 50.3%; n = 1,993; p = 1) or frozen ET (FSHr: 31.8% vs. FSHr+hMG: 33.8%; n = 2,508; p = 1). Limitations, reasons for caution The retrospective and single-center nature of the study would be its main limitations. It is essential to emphasize that these results are only applicable within the oocyte donation program. Wider implications of the findings Based on our findings, the use of exogenous FSHr alone is likely adequate in the GnRH antagonist protocol for optimal ovarian stimulation of donors, leading to the production of high-quality embryos and successful clinical outcomes. Trial registration number Not Applicable

P-640 Dynamics of IGF signalling during the ovulatory peak in women undergoing ovarian stimulation

Abstract Study question How is the IGF system expressed and regulated during the midcycle surge in women? Summary answer The IGF system becomes downregulated after ovulation trigger (OT) highlighted by a significant upregulation of the inhibitor, stanniocalcin-1, and a downregulation of protease-induced IGF release. What is known already IGF signalling is known to affect human ovarian follicular function during growth and development. Particularly during the preovulatory stage, IGF activity appears to be highly significant and has been proposed as one of the primary factors contributing to the remarkable mitotic activity observed in the granulosa cells (GCs). However, the role and regulation of the IGF system is unknown during the ovulatory peak, which is characterized by profound changes in GC function. Study design, size, duration Follicular fluid (FF) and GCs were collected from fifty women during the ovulatory peak from two specific time-points. One sample was obtained before oocyte pick up (OPU): before OT (T = 0 h (n = 23)), at 12 h (n = 10), 17 h (n = 6), or 32 h (n = 11) after OT, and one sample was obtained at OPU 36 h after OT (n = 50). Participants/materials, setting, methods Fifty women receiving fertility treatment at the Fertility Clinic, Department of Gynaecology and Obstetrics, Holbæk Hospital, Denmark, were included. For ethical reasons, only women who had developed more than eight mature follicles at their final control visit before OT were approached and asked for possible participation. Gene expression profiles were assessed by microarray analysis of GCs. Intrafollicular levels of IGF-related proteins were assessed with immunoassays and a proteinase assay was used to quantify activity. Main results and the role of chance This study presents a novel insight into the dynamics of IGF bioavailability within human ovarian follicles during the midcycle surge of gonadotropins. Notably, this investigation reports a significant downregulation of genes promoting IGF signalling, i.e., IGF-2, PAPPA, and IRS1, along with a concurrent upregulation of genes associated with IGF binding and inactivation, including IGFBPs, IGF2R, and STC1. Particularly, the substantial increase in the inhibitor, stanniocalcin-1 (STC1), at both gene and protein levels likely plays a key role in the downregulation of IGF signalling. Additionally, this study reveals a marked reduction in intrafollicular PAPP-A proteolytic activity after OT, further emphasizing the importance of PAPP-A within human ovaries. In addition, this study indicates a pronounced decline in GC mitotic activity during the midcycle surge, as evidenced by the downregulation of proliferation markers, including MKI67, E2F1, E2F8, and FOXM1, highlighting a substantial decrease in GC proliferation rate during this critical phase. Previous research has demonstrated that IGF signalling stimulates the proliferation and differentiation of cultured human GCs. Therefore, the significant changes in IGF bioavailability observed in human GCs during the ovulatory surge suggest an essential role of IGF signalling in controlling the proliferation and differentiation of GCs within the preovulatory follicle. Limitations, reasons for caution This study highlights the need for future functional studies to confirm a direct mechanism to account for the abrupt cessation of GC proliferation. Differences between using hCG or GnRH agonist for final maturation of follicles were not shown, thus future studies should be powered to reveal effects of the protocols. Wider implications of the findings These data suggest that downregulation of IGF signalling mediated by increased STC1 expression is instrumental for the sudden cessation in GC proliferation and onset of differentiation during the ovulatory peak. Furthermore, this study implies importance of IGF-independent functions of STC1, especially during the ovulatory peak, where elevated levels are observed. Trial registration number Not applicable