Ovarian Stimulation Research Articles

P-598 Novel inactivating homozygous mutation of the luteinizing hormone/choriogonadotropin receptor (LHCGR) and first live birth after in vitro maturation (IVM): a breakthrough

Abstract Study question How can pregnancy and live birth be achieved in patients with inactivating homozygous luteinizing hormone/choriogonadotropin receptor (LHCGR) mutation? Summary answer We report the first live birth after IVM in a patient with a novel homozygous inactivating LHCGR mutation (exon 6,c.470A>G). What is known already LH plays a fundamental role in female reproductive physiology and is responsible for steroidogenesis, oocyte maturation, ovulation and subsequent progesterone production by the corpus luteum. LH binds to the LHCGR located on the membrane of theca cells and mature granulosa cells. Inactivating mutations of the LHCG receptor lead to the impossibility to obtain final oocyte maturation both during natural cycles and after ovarian stimulation for in vitro fertilization purpose. Until now, egg donation represented the only option to treat their infertility. Study design, size, duration A case report. Participants/materials, setting, methods A 35 year-old nulliparous patient was referred to our university hospital for primary infertility. Main results and the role of chance The 35-year-old nulliparous patient presented with primary spaniomenorrhea but timely and spontaneous onset of secondary sexual characteristics. Serum LH levels were high (ranging from 15 to 30 IU/L) and to a lesser extent so were FSH levels. The ovarian reserve was normal for age, as assessed by serum AMH levels and ultrasound. There was no argument for polycystic ovarian syndrome, 21-hydroxylase deficiency, Cushing’s syndrome or hyperprolactinemia. Two previous attempts of controlled ovarian stimulation with gonadotropins and ovulation trigger with hCG and GnRH-agonist trigger had failed, resulting in low estradiol levels despite correct follicular growth on ultrasound and absence of ovulation after trigger. We identified by genetic analysis a novel homozygous inactivating LHCGR mutation (exon 6, c.470A>G) that had never been described previously. IVM was performed. A total of 7 oocytes were obtained after IVM, resulting in 4 Day 3 embryos. All embryos were frozen. Subsequently, 2 Day 3 embryos were replaced after endometrial preparation by hormone replacement therapy. The patient became pregnant and gave birth to a healthy baby. Two Day 3 embryos remain. Limitations, reasons for caution By definition, a case-report requires further studies to confirm our findings. Wider implications of the findings We describe a novel inactivating LHCGR mutation with subsequent live birth after IVM. As a growing number of gonadotropin receptor mutations are identified, this live birth successfully obtained places IVM as the only reliable option for these patients to conceive with their own eggs. Trial registration number not applicable

O-086 Risk of serious adverse event after fertility preservation procedures: a comparison of cancer and non-cancer patients

Abstract Study question Do cancer patients have a higher risk of serious adverse event associated to fertility preservation procedures compared to non-cancer patients ? Summary answer No increased risk of adverse event after fertility preservation procedures was identified in cancer patients compared to non-cancer patients undergoing fertility preservation for other indications. What is known already Current recommendations encourage a prompt and exhaustive discussion on the different techniques of fertility preservation that can be performed in cancer patients of reproductive age prior to cancer treatments. Although cryopreservation of mature oocytes and/or embryos is the technique of reference in the absence of contraindication, ovarian stimulation and subsequent oocyte retrieval are associated to complications. Cancer patients might present an additional risk given tumoral hypervascularity and proinflammatory environment, as well as possible immune or coagulation disorders. However, whether cancer patients have an increased risk of serious adverse event associated to fertility preservation procedures compared to non-cancer patients remains unknown. Study design, size, duration A bicentric, retrospective study between January 1st, 2014 and December 31st, 2021. Participants/materials, setting, methods All women undergoing fertility preservation procedures by oocyte and/or embryo cryopreservation after controlled ovarian stimulation or in vitro maturation.The main endpoint was the occurrence of a serious adverse event (hospitalization for ovarian hyperstimulation syndrome, hemorrhage, infection, thromboembolic event, ovarian torsion, acute urine retention or death) in cancer patients compared to non-cancer patients undergoing fertility procedures. Main results and the role of chance A total of 4476 cycles (n = 3180 patients) were included, of which 3761 after controlled ovarian stimulation and 715 in vitro maturation cycles. Among the 4476 cycles, 1678 were performed in an oncological context (n = 1546 cancer patients) and 2798 were fertility preservation cycles for an indication other than cancer (n = 1634 patients). A total of 29 serious adverse events associated to fertility preservation procedures were registered, of which 17 intraperitoneal hemorrhages, 8 cases of ovarian hyperstimulation syndrome, 3 cases of infection and 1 case of acute urine retention. The risk of serious adverse event associated to fertility preservation procedures was not significantly different between cancer patients and non-cancer patients (0.36% vs. 0.82%, respectively, P = 0.06). Young age (P = 0.002), a higher number of oocytes retrieved (P = 0.006) and a higher number of oocytes vitrified (P = 0.002) were significantly associated to the risk of presenting a serious adverse event after fertility preservation. Limitations, reasons for caution Although rates of serious adverse events in our study are similar to that reported in previous literature and that the declaration and registration of any serious adverse event is mandatory according to French legislation, it is possible that not all serious adverse events were declared and registered. Wider implications of the findings Given the trend of delaying parenthood and the improved survival rates after cancer treatments, these findings are of particular importance, emphasizing the safety of performing fertility preservation procedures for cancer patients of reproductive age who might have a pregnancy desire after cancer treatment. Trial registration number not applicable

P-630 Assessing Bologna and POSEIDON criteria as predictors of PGT-A in Poor Ovarian Response: A comparative analysis

Abstract Study question Do Bologna or POSEIDON criteria more accurately predict PGT-A outcomes in poor ovarian response, considering aneuploidy rates and clinical outcomes? Summary answer Comparing Bologna and POSEIDON criteria highlights higher aneuploidy rates in Bologna patients, with no significant differences in mosaicism rate or clinical outcomes in either group. What is known already Ovarian reserve stands out as the primary factor influencing reproductive senescence. Approximately 9-24% of individuals undergoing ovarian stimulation are categorized as ‘low-responders’. Key indicators of Poor Ovarian Response (POR) include age, antral follicle count (AFC), Anti-Müllerian Hormone (AMH), and response to controlled ovarian stimulation. While some studies link ovarian reserve to embryo quality, others dispute any correlation with embryo abnormalities. The Bologna criteria classify patients meeting at least two of the following: advanced maternal age, low AFC, and AMH. The more precise POSEIDON criteria combine these factors, forming four distinct groups for classification. Study design, size, duration We conducted a retrospective case-control study, examining PGT-A results of 2740 embryos derived from 797 IVF cycles conducted in our clinic between 2021 and 2022. Trophoectoderm biopsies, taken at D + 5/6, underwent Next-Generation Sequencing. Embryos were vitrified and transferred after analysis. Regarding the interpretation of the results, embryos with ≤25% cells aneuploids were considered euploid, between 25% and 50% were classified as mosaic and those with >50% cells were considered aneuploid. Participants/materials, setting, methods All patients used their own oocytes. Bologna and POSEIDON criteria were used for the classification of POR and non-POR patients. Univariate analysis was performed using Pearson’s chi-square statistical test for categorical variables and binary logistic regression to compare the rates of aneuploidy and embryonic mosaicism, pregnancy rate miscarriage, ongoing pregnancy rate and implantation rate with the above variables taking into account possible confounding factors. Main results and the role of chance Patient ages ranged from 22 to 47 years, with a mean of 38.9 years. In Bologna groups, mean ages were 41.15 years for Bologna and 38.43 years for the control. For POSEIDON: 32.47 group I, 39.85y group II, 32.11y group III, 40.41y group IV and 38.24y control group of the classified by POSEIDON criteria. The mean AFC was 10.95 and the AMH value was 13.15pmol/L. Among 797 cycles, 59.16% (449/797) met POR criteria by POSEIDON, distributed across groups: 1.19% (9/797) in group I, 1.32% (10/797) in group II, 22.66% (172/797) in group III and 33.99% (258/797) in group IV. Using Bologna criteria, 17.74% (486/797) were classified as POR. Our findings reveal that individuals identified with POR by Bologna criteria exhibit a significantly elevated incidence of embryo aneuploidy (78.8% POR patients vs. 59.9% control patients; p = 0.004). However, no such distinction was observed when employing the POSEIDON criteria for classification. In terms of embryo mosaicism, no notable differences were detected between POR and non-POR patients under both Bologna and POSEIDON criteria. Furthermore, no significant variations in clinical data were observed between the two groups, even after correcting for maternal age. Limitations, reasons for caution The study is constrained by the inherent limitations of a retrospective design and a restricted sample size. Moreover, the complexity and heterogeneity involved in classifying patients with POR contribute to additional challenges in the interpretation of results. Wider implications of the findings The study indicates that diminished ovarian reserve does not significantly augment the probability of embryo aneuploidies. Particularly noteworthy is the observation that young women with low ovarian reserve do not exhibit an increased susceptibility to aneuploidies. This finding holds implications for understanding reproductive outcomes among ovarian reserve variations. Trial registration number No aplicable

P-650 Cumulative live birth rate after use of capacitation in vitro maturation in women with predicted excessive response to ovarian stimulation: an analysis of 1,563 cycles

Abstract Study question What is the cumulative live birth rate in biphasic (capacitation) in vitro maturation (CAPA-IVM) cycles in women with predicted excessive response? Summary answer The cumulative live birth rate achieved after CAPA-IVM in women with predicted excessive response was 37.8%. What is known already In vitro maturation (IVM) is an alternative infertility treatment for women at high risk of complications during conventional in vitro fertilisation with ovarian stimulation. There is debate about the merits of a newer biphasic approach (capacitation [CAPA]-IVM) versus standard IVM. At centres where it is used, CAPA-IVM has increased the maturation rate, and therefore the number of embryos available for transfer. However, there is a lack of data from large numbers of CAPA-IVM cycles, especially cumulative outcomes. Study design, size, duration This analysis included data from 1,563 individuals who underwent CAPA-IVM at a tertiary IVF center in Ho Chi Minh City, Vietnam from January 2016 to December 2023. Participants/materials, setting, methods All CAPA-IVM cycles in women with predicted excessive response (polycystic ovary syndrome or high antral follicle count) were included. Mean age was 29.6±3.5 years. Median duration of infertility was 3.3±2.5 years. CAPA-IVM was the first assisted reproductive technology in 90.5% of participants. Cumulative live birth rate was defined as the number of live births after using all embryos generated from a CAPA-IVM cycle. Main results and the role of chance Cumulative rates of clinical pregnancy, ongoing pregnancy and live birth were 54.9%, 44.4% and 37.8%, respectively. The median proportion of mature oocytes per cumulus-oocyte complex was 61.3% (IQR 50.0–73.3) and the median proportion of fertilized oocytes per cumulus-oocyte complex was 72.2% (IQR 55.6-85.7). The median total number of day-3 embryos per patient was 4.0 [IQR 3.0–7.0] and the total number of good day-3 embryos per patient was 3.0 [IQR 2.0–5.0]. The proportion of patients with no embryo was 5.2%. The number of frozen embryo transfer cycles was 1 (53.6% of patients), 2 (24.9%), 3 (7.0%), 4 (0.8%) or 5 (0.3%); 7.9% of patients had not undergone transfer of day-3 embryos at the time of analysis. Median [IQR] number of embryos and good embryos transferred was 2.0 [2.0–4.0] and 2.0 [1.0–2.0], respectively. No case of ovarian hyperstimulation syndrome recorded. Limitations, reasons for caution The characteristics of the study population (relatively young, lean women from Vietnam with predicted excessive response to ovarian stimulation) limit the external generalisability of the findings. Wider implications of the findings The cumulative live birth rate from all CAPA-IVM cycles performed in women with predicted excessive response at our centre was comparable to that of IVF. CAPA-IVM could be an alternative for this selected group of patients to avoid ovarian hyperstimulation. Trial registration number not applicable

P-396 Comparison of luteal support protocols in fresh IVF/ICSI cycles: A network meta-analysis

Abstract Study question What is the optimal LPS in fresh cycles in agonist and antagonist cycles? Summary answer Vaginal progesterone, with the addition of SCGnRH-a results in improved clinical pregnancy and live birth events in both GnRH-agonist and antagonist ovarian stimulation protocols. What is known already Despite the proven superiority of various Luteal Phase Support protocols (LPS) over placebo in view of improved pregnancy rates in fresh cycles of IVF (in vitro fertilization) and ICSI (intracytoplasmic sperm injection) cycles, there is ongoing controversy over specific LPS protocol selection, dosage, and duration. Study design, size, duration Network Meta-analysis. Twelve databases, namely Embase (OVID), MEDLINE (R) (OVID), GlobalHealth (Archive), GlobalHealth, Health and Psychosocial Instruments, Maternity & Infant Care Database (MIDIRS), APA PsycTests, ClinicalTrials.gov, HMIC Health Management Information Consortium, CENTRAL, Web of Science, Scopus and two prospective registers, MedRxiv, Research Square were searched from inception to Aug.1st, 2023.The study was prospectively registered under the PROSPERO database. Participants/materials, setting, methods Only RCTs were included. Primary outcomes included clinical pregnancy and live birth events, while secondary outcomes included biochemical pregnancy, miscarriage, multiple pregnancy and OHSS events. Bayesian network meta-analysis (NMA) model was employed for outcome analysis, presenting fixed effects, odds ratios (ORs) with 95% credibility intervals (CrIs). Vaginal Progesterone (VP) was considered the reference LPS for the purposes of the NMA given its’ clinical relevance. Main results and the role of chance Seventy-six RCTs, comparing 22 interventions, and including 26536 participants were included in the present NMA.Combinatorial regimens, with subcutaneous GnRH-a (SCGnRH-a) on a vaginal progesterone base and oral oestrogen (OE) appeared to overall improve clinical pregnancy events; VP+OE+SCGnRH-a [OR 1.57 (95% CrI 1.11 to 2.22)], VP+SCGnRH-a [OR 1.28 (95% CrI 1.05 to 1.55)] as well as live pregnancy events, VP+OE+SCGnRH-a [OR 8.81 (95% CrI 2.35 to 39.1)], VP+SCGnRH-a [OR 1.76 (95% CrI 1.45 to 2.15)]. Equally, the progesterone free LPS, intramuscular human chorionic gonadotrophin, [OR 9.67 (95%CrI 2.34, 73.2)] was also found to increase live birth events, however was also associated with an increased probability of ovarian hyperstimulation, [OR 1.64 (95%CrI 0.75, 3.71)]. Of all LPS protocols, VP+SC GnRH-a was found to significantly reduce miscarriage events, OR 0.54 (95% CrI 0.37 to 0.80). Subgroup analysis according to ovarian stimulation (OS) protocol revealed that the optimal LPS across both long and short OS, taking into account increase in live birth and reduction in miscarriage as well as OHSS events, was VP+SCGnRH-a, with an OR 2.89 [95%CrI 1.08, 2.96] and OR 2.84 [95%CrI 1.35, 6.26] respectively. Limitations, reasons for caution Given the anticipated diversity of measured outcomes, a Bayesian meta-synthesis approach has been adopted to account for the expected heterogeneity and to incorporate modelling flexibility by allowing for posterior distributions interpreted as SUCRA probabilities with the later enabling crisper communication of the uncertainty in the treatment effects estimates. Wider implications of the findings Overall, NMA data suggest that combinatorial treatments, with the addition of SCGnRH-a on a VP base result in improved clinical pregnancy and live birth events in both GnRH-agonist and antagonist ovarian stimulation protocols. Trial registration number Not applicable

P-126 The impact of ICSI versus IVF on the reproductive outcomes of couples with non-male factor infertility and frozen-thawed embryo transfer cycles

Abstract Study question Does Intracytoplasmic Sperm Injection (ICSI) improve reproductive outcomes in patients with non-male factor infertility undergoing Frozen-Thawed Embryo Transfer (FET) treatment? Summary answer ICSI showed slightly improved clinical outcomes compared to IVF, but was associated with higher preterm birth rates and low birthweight when twins were born. What is known already The use of ICSI has seen a significant surge globally, particularly in Europe and the USA, as a solution for fertilization failure resulting from male factor infertility. FET presents a viable option for those considering additional children. Numerous studies have investigated the effectiveness of ICSI in couples with non-male factor infertility undergoing fresh embryo transfer in ovarian stimulation cycles. However, there is a dearth of evidence demonstrating whether ICSI, compared to conventional IVF (cIVF), could influence reproductive outcomes in couples with non-male factor infertility undergoing FET treatment. Study design, size, duration This retrospective cohort study included 10,143 cycles from 6,206 couples who underwent FET at the Third Affiliated Hospital of Zhengzhou University between January 2016 and September 2022. Participants/materials, setting, methods Patients were categorized into two groups based on the insemination methods used for the transferred embryos. Patients were excluded if : 1) Embryos were biopsied and tested; 2) Oocytes had been vitrified; 3) Embryos were derived from donor oocytes, AOA treatment, or rescue ICSI; 4) Embryos that were not transferred; and 5) They had undergone fresh embryo transfer. PSM at a ratio of 1:1 was utilized to ensure comparability of reproductive outcomes. Main results and the role of chance Post-PSM, the general characteristics were comparable across both groups. The clinical pregnancy rates (37.6% vs 40.0%, P = 0.311), miscarriage rates (21.4% vs 23.1%, P = 0.597), and live birth rates (28.2% vs 30.4%, P = 0.329) exhibited no significant disparity post-PSM between the two groups. Notably, a marginally elevated live birth rate was observed in the ICSI group when blastocysts were transferred to the women (39.8% vs 48.3%, P = 0.050). However, the GEE models indicated that ICSI did not enhance the likelihood of clinical pregnancy, miscarriage, and live birth relative to IVF in women with non-male factor infertility. Following adjustments for variables, ICSI yielded consistent OR values [1.14(0.92-1.42), P = 0.241; 1.08(0.72-1.61), P = 0.703; and 1.16(0.92-1.46), P = 0.220, respectively]. The perinatal outcomes were similar between the two grousps. However, a significantly higher incidence of preterm birth was observed in the ICSI group compared to the cIVF group (20.0% vs 12.5%, P = 0.026). While pregnancy complications were comparable between the two groups, neonates born as twins in the ICSI group exhibited significantly reduced live birth-weight [2520.8(572.9) vs 2691.9(423.7), P = 0.043] and birth length [47.5(2.8) vs 48.5(2.3), P = 0.031]. Correspondingly, the rate of low birthweight was significantly higher in the ICSI group (38.9% vs 21.0%, P = 0.025). Limitations, reasons for caution The retrospective design may lead to selection bias among the included patients. The use of ICSI in ART has been strictly regulated in our country, limiting the sample size and potentially reducing the statistical power. Wider implications of the findings The value of ICSI should be thoroughly discussed with patients with non-male factor infertility before ovarian stimulation. Further research is needed to better understand the impact of ICSI on reproductive and neonatal outcomes in this population. Trial registration number 2021YFC2700602

O-058 Newly identified female mutations causing oocyte maturation defect and embryo developmental arrest

Abstract Female infertility is a complex issue affecting a significant number of women. In the United States, among married women aged 15–49 years with no prior births, approximately one in five (19%) were unable to get pregnant after one year of trying. In addition, approximately one in four (26%) women in this group had difficulty getting pregnant or carrying a pregnancy to term. For women under 35 years of age, infertility is defined as a lack of success within one year, while for women aged 35 and older, it is within six months. Various factors, such as genetic, endocrine, physiological, anatomical, and immunological irregularities within the reproductive system, can affect a woman's chances of achieving pregnancy and delivering a healthy child. Among these factors, oocyte maturation is an important prerequisite for successful fertilization and subsequent embryonic development. In Medically Assisted Reproduction (MAR), the meiotic maturation of oocytes is induced by human chorionic gonadotropin (hCG) injection, which mimics the natural endogenous luteinizing hormone (LH) surge during the menstrual cycle. Although it is common for a few oocytes to remain immature despite ovarian stimulation and hCG administration, generally, immature oocytes have the competency to spontaneously mature in vitro. However, oocyte maturation is a sophisticated process involving multiple genes or protein molecules. Therefore, pathogenic variations in the genomic sequence or functional defects in any molecule that affects meiosis may lead to impaired oocyte maturation. While complete failure of all oocytes to mature in vivo is extremely rare, understanding the molecular aetiology of oocyte maturation is crucial for addressing infertility issues related to this process and improving fertility outcomes. The transition from the cleavage to the blastocyst stage often represents a significant bottleneck, with nearly 10% of fertilized eggs arrested at the cleavage stages. Developmental arrest of the preimplantation embryo is characterized by the cessation of cellular division for at least 24 h. Various factors originating from both embryonic and parental sources contribute to arrest of early stage embryo development. The genetic roots of developmental arrest were examined by considering both the parental causes of infertility and factors within the embryo. Examination revealed shared elements, regardless of the source of origin. Chromosomal abnormalities, abnormal preimplantation development, and monogenic variations have been reported to cause embryonic developmental arrests. Recently, deficiencies in oocyte maturation and embryo development have been categorized as part of the oocyte/zygote/embryo arrest (OZEMA) phenotype in the Online Mendelian Inheritance in Man (OMIM) database. A latest extensive review of monogenic causes associated with female infertility identified 23 genes with a total of 27 gene disease relationships (GDRs) for the OZEMA phenotype. Seventeen GDRs were classified as having at least moderate evidence of involvement in OZEMA, in addition to ten GDRs with less substantial evidence. Several additional genes were subsequently identified. This presentation will provide an overview of gene defects linked to the OZEMA phenotype, discuss the current status and future prospects of pre-MAR screening of females with OZEMA, and assess a novel workflow for modern genetic diagnosis to maximize the benefit of the patient.

P-542 Bidirectional signaling between oocytes and ovarian support cells (OSCs) during in vitro maturation results in improved oocyte gene expression

Abstract Study question Are the gene expression profiles of ovarian support cells (OSCs) and cumulus-free oocytes bidirectionally influenced by co-culture during in vitro maturation (IVM)? Summary answer OSC gene expression is modulated by oocyte presence and OSC-IVM matured oocytes display transcriptomic resemblance to in vivo matured oocytes potentially due to OSC-oocyte crosstalk. What is known already The application of IVM holds a significant interest to improve infertility treatment. We previously showed the development of human OSCs generated from human induced pluripotent stem cells (hiPSCs) with ability to improve the maturation rates of immature human cumulus oocyte complexes (COCs) and embryo formation rates from minimal ovarian stimulation cycles (Piechota et al. 2023). We recently demonstrated that OSC-IVM can also be used to improve the nuclear maturation rate of human denuded oocytes from conventional stimulation cycles. Study design, size, duration We aimed to determine how gene expression changed in oocytes and OSCs by OSC-IVM co-culture. Immature fresh denuded oocytes (n = 141) were collected and randomized for IVM without OSCs (Media-IVM) (MediCult; n = 59) or with OSCs (OSC-IVM) (OSCs+MediCult; n = 82) for 24-28h. Subject enrollment ranged from 12/01/2023-06/30/2023. OSCs were collected for analysis pre-IVM (time 0h; n = 3), and post-IVM with (n = 3) and without (n = 3) immature denuded oocyte co-culture. Participants/materials, setting, methods 47 fertility patients undergoing conventional ovarian stimulation donated immature denuded oocytes (GV or MI oocytes) for research, which were allocated between either the Media-IVM or OSC-IVM conditions. In vivo matured oocytes (IVF-MII) were used as controls. Single oocyte RNA sequencing (RNA-seq) was performed after IVM culture, including both mature oocytes or stalled immature oocytes, alongside IVF-MII oocytes. Bulk RNA-seq was performed on OSCs and primary cumulus cells were used as a reference control (n = 7). Main results and the role of chance RNA-seq analysis demonstrated in the absence of oocytes, OSCs retain their global transcriptomic signature during IVM, maintaining or upregulating expression of CYP19A1, MDK, NR2F2, FOXL2, and CD82 and downregulating FSHR. When co-cultured with oocytes, OSCs shifted their global transcriptomic profile to resemble primary cumulus cells. In OSCs, we identified upregulation of IGF2, EGF, and IGFBP4, and downregulation of AMHR2, EGFR and IGFBP2 in the presence of oocytes, indicating oocyte-directed remodeling of OSC gene expression. Differential gene expression analysis in oocytes comparing MIIs and GVs post-IVM identified 31 genes differentially enriched and 353 genes differentially depleted in MIIs after co-culture with OSCs compared to 37 and 230 genes respectively without OSCs. IVF MII gene expression did not differ from OSC-IVM MII oocytes but did significantly differ from Media-IVM MII gene expression (p = 0.0008). Pathway enrichment analysis demonstrated broad similarity between IVF and OSC-IVM MIIs for Unfolded Protein Response, Myc Targets, and Oxidative Phosphorylation, while Media-IVM uniquely showed enrichment in DNA Damage and Spindle Assembly pathways. Media-IVM produced MIIs enriched uniquely for genes involved in electron transport chain (ETC) and oxidative phosphorylation (OXPHOS), which were not found in OSC-IVM or IVF MIIs. Limitations, reasons for caution The number of oocytes utilized in this study was limited. Additionally, as this study used rescue IVM as a model, it is likely that approaches using cumulus enclosed oocytes and traditional IVM may differ. Wider implications of the findings Bidirectional signaling between OSCs and oocytes may contribute to an improved in vitro environment that supports oocyte nuclear and cytoplasmic maturation. Therefore, oocytes matured in the presence of OSCs are more similar to oocytes matured in vivo and display a pathway enrichment profile associated with a higher oocyte developmental competence. Trial registration number not applicable

P-699 High levels of total FSH during COS is detrimental to oocyte development in good responders: results from a three-year retrospective, multicenter study

Abstract Study question Are elevated doses of follicle stimulating hormone (FSH) detrimental to oocyte maturation and the efficacy of ovarian stimulation in good responders? Summary answer Elevated FSH levels reduce the number of oocytes collected from good responders. Patients receiving lower total FSH doses had optimal and higher maturation rates. What is known already There is an inverse relationship between the dose of exogeneous follicle stimulating hormone (FSH) and the number of oocytes retrieved. This relationship is independent of patient age or health and implies that excessive FSH doses administered during artificial reproductive technologies (ART) may be detrimental to oocyte maturation. Study design, size, duration This three-year retrospective, multicenter study included 1,075 oocyte donor cycles performed in three IVF clinics between January 2020 and December 2023 with at least a six-month interval between each cycle. Donors were all considered good responders and divided according to the total dose of FSH received per cycle (n = 289 cycles with <1,700 IU FSH; 400 cycles with 1,700 to 2,900 IU FSH; and 386 cycles with >2,900 IU FSH). Participants/materials, setting, methods The mean oocyte donor age was between 26.13 and 27.45 years old. The mean BMI for all three groups was 21. The association between the total FSH dose and serum anti-Müllerian hormone (AMH) level, follicle-to-oocyte index (FOI), number of oocytes retrieved, and oocyte maturation was assessed using the Student’s t-test (parametric) or Mann-Whitney-U test (non-parametric). Main results and the role of chance There were no significant differences in the mean serum AMH levels (5.31 vs. 5.27 vs. 5.13 ng/mL, respectively) and FOI (81.1 vs. 80.2 vs. 81.5, respectively) of patients who received different total doses of FSH. However, the number of oocytes retrieved from each group was inversely related to the total dose of FSH received (24.4 vs. 22.9 vs. 21.01 oocytes, respectively; p < 0.05) Limitations, reasons for caution Full characterization of the oocytes and their developmental potential was outside the scope of this retrospective study. Wider implications of the findings Gaining a better understanding of the complex interplay of gonadotropins throughout folliculogenesis can help optimize ovarian stimulation protocols to maximize the number of mature and developmentally competent oocytes recovered for clinical use. Trial registration number non applicable

O-300 Dydrogesterone versus GnRH-antagonists to supress the LH surge in IVF/ICSI cycles

Abstract Study question Does Dydrogesterone block premature Luteinaizing hormone surge and ovulation during the controlled ovarian stimulation without compromising of IVF/ICSI outcomes? Summary answer Dydrogesterone and GnRH-antagonist have equal effectivness for prevention of premature luteinizing hormone surge and ovulation without any adverse effect on laboratory and clinical results. What is known already Premature LH surge and premature ovulation during the controlled ovarian stimulation is one of the main causes of cycle cancellation.Traditionally, during in-vitro fertilization for controlled ovarian stimulation to prevention of premature LH surge clinicians use GnRH antagonists. Recent data indicates that premature LH surge may be prevented also by progestins, since they have a role in suppression of preovulatory LH surge. In past, progesterone was not used during ovarian stimulation due to the negative effect on endometrial receptivity, while nowadays advanced techniques give possibility to use it as an alternative to a GnRH antagonists using the freeze-all strategy. Study design, size, duration In this prospective, randomized study were participated sixty -seven egg donors. Sudy was conducted on the basis of Clinic Leadermed (Georgia, Tbilisi) from October of 2021 to November 2023. The Ethics Committee of clinic Leadermed approved this study and appropriate informed consent was obtained from all participants. Participants/materials, setting, methods Recombinant gonadotropin was administered for control ovulation stimulation in oocyte donors. According to the ovarian response HMG was added. Intervention group (group I, n = 34) received 20 mg of Dydrogesterone from the first day of stimulation till trigger day and the control group (group II, n = 33) received GnRH-antagonist when the leading follicle reached 14 mm in diameter till trigger day. Triptorelin acetate 0.3 mg was administered when at least 3 follicles reached ≥18 mm in diameter. Main results and the role of chance There were no statistically significant differences in the oocyte donors age, BMI and AMH levels between two groups. None of the participants experienced a premature LH surge and ovulation. There was no statistically significant difference in the number of MII oocytes (23,7 vs 25.9 p = 0.3). The duration of stimulation and total dose of gonadotropins was similar in both groups (9.6 vs 9.9 days, p = 0.41), (2269.2 IU vs 2423.4 IU, p = 0.08) respectively. There was no difference in fertilization rates (85.62% vs 83.94%, p = 0.41), as well as blastulation rates and top-quality blastocysts (65.78% vs 69.72%, p = 0.17; 54.50% vs 51.75%, p = 0.21). Regarding clinical pregnancy rate, the results were similar, with no significant differences between two groups (66.28% vs 68.10%, p = 0.8). Limitations, reasons for caution The limitation of the study is that embryotransfer was performed as in patients (age till 49years), as well as in surrogate mothetrs (age till 41 years). Wider implications of the findings Dydrogesterone and GnRH-antagonist has equal effectiveness for prevention of premature LH surge without affecting of IVF outcomes. It is a financially profitable and easy to use which can be used as in oocyte donors as well as in patients where embryo transfer is not planned in the current cycle. Trial registration number non-clinical trial

P-634 Medroxyprogesterone acetate as an alternative to gonadotropin-realeasing hormone antagonist in vitrified oocyte donation cycles: embryo assessment and clinical outcome

Abstract Study question Could Medroxyprogesterone Acetate (MPA) be a good alternative to gonadotropin-realeasing hormone (GnRH) antagonist in vitrified oocyte donation cycles? Summary answer MPA is a good alternative to GnRH antagonist in vitrified oocyte donation cycles, ensuring comparable embryo quality and clinical outcome. What is known already Progestin-primed ovarian stimulation (PPOS), such as oral administration MPA in the follicular phase appears to be an effective alternative to conventional protocols, as it prevents premature LH surge and ovarian hyperstimulation syndrome. The drawback of these treatments is that it requires vitrification of oocytes or embryos because the endometrium is out of phase when embryo transfer is performed. Our previous studies have shown similar oocyte retrieval rates in fertility preservation cycles and comparable clinical outcomes in fresh donation cycles. Our objective is to expand evidence on PPOS, extending its success to new populations like vitrified donation cycles. Study design, size, duration This retrospective cohort study performed at IVI Valencia compared the effect of the MPA (10 mg/day) versus ganirelix (0.25 mg/day) on egg donors undergoing ovarian stimulation whose eggs were vitrified after retrieval. Donor cycles were divided intro groups, with 495 cycles in the MPA group and 307 in the ganirelix group. After oocyte donations and warming, the artificial intelligence based embryo assessment and clinical outcome were compared and analyzed for the two study populations Participants/materials, setting, methods 497 recipients using oocytes from the MPA group and 307 from the ganirelix group were included in the study. Post-oocyte donation and warming, a follow-up of 10,108 oocytes was performed, analyzing survival, fertilization, and blastocyst development. The embryo score obtained with the deep learning based model iDAScore v2, and the ASEBIR evaluation performed by embryologists were compared between both study populations. Finally, comprehensive clinical outcome comparisons were conducted between the two study populations. Main results and the role of chance The mean number of thawed oocytes was significantly different* between the two groups (12.80±3.54 in the MPA group vs. 12.20±3.58 in the antagonist group). Survival, fertilization, and blastocyst development rates showed no significant differences (89.83%, 76.38% and 66.22% respectively in the MPA group and 88.67%, 76.75% and 64.29% in the antagonist group). However, ASEBIR embryo assessment showed a significantly higher percentage of embryos classified as A and B in MPA group* (10.5% and 58.0% respectively vs. 7.2% and 53.6%), and more C embryos* in the antagonist group (34.3% vs. 39.2%). Artificial intelligence-based embryo assessment revealed no significant differences between the two groups*, with mean evaluations being 4.97±2.60 in the MPA group and 5.07±2.68 in the antagonist group. Regarding clinical outcomes, the MPA group had significantly higher number of frozen embryos per cycle* (4.08±2.07 in the MPA group vs. 3.65±2.00 in the antagonist group) but no disparities in implantation, clinical pregnancy, ongoing pregnancy, live birth and cumulative live birth rates. A generalized estimation equation highlighted that the study group (MPA or antagonist) did not significantly impact the live birth rate, but was significantly influenced instead by the number of thawed oocytes, recipient BMI, and transferred embryo quality assessed with iDAScore*. (*p<.05) Limitations, reasons for caution This project is limited by its retrospective and single-center nature. Despite being the largest sample size ever reported for PPOS in vitrified donation cycles, the number of patients included could be considered low. Consequently, it would be advisable to conduct a multicenter RCT to confirm the conclusions of this study. Wider implications of the findings The administration of MPA as a gonadotropin adjuvant demonstrates clinical outcomes comparable to those achieved with ganirelix in vitrified oocyte donation cycles. Its user-friendly application encourages the wider adoption of this protocols. These promising results promote the widespread use of MPA-based protocols in vitrified oocyte donation cycles. Trial registration number not applicable

P-645 A machine learning model for optimal trigger day recommendation

Abstract Study question Could AI be used for trigger day recommendations to improve the number of M2 oocytes retrieved in IVF processes? Summary answer The use of AI for trigger day recommendations can improve the number of M2 oocytes retrieved in IVF processes by 1 on average. What is known already One of the most important decisions during ovarian stimulation during IVF cycles is when to trigger follicular maturation. Optimally timed trigger injection should maximize the number of retrieved high-quality oocytes. While these decisions are commonly made based on follicle sizes, hormone levels, and patient parameters, they are subjective and the criteria vary across medical centers and physicians. Numerous research studies are exploring how follicle sizes and other parameters translate to stimulation outcomes, but only in recent years, the use of artificial intelligence in decisions about the day of the trigger has become one of the main fields of interest. Study design, size, duration A retrospective study was made on 1085 IVF cycles conducted between 2019 and 2021 at 6 IVF centers in Poland. Processes were selected to have at least one set of ultrasound cine-loop videos for both ovaries from a maximum of three days before trigger day. Additionally, data on age, AMH, estradiol level, endometrium thickness, and the process outcome (MII oocytes number) was collected. Follicles were measured using the FOLLISCAN system. Participants/materials, setting, methods The recommendation algorithm uses a model predicting the number of MII oocytes retrieved if the trigger was applied on each of the three days following examination. The day with a maximum expected number of oocytes is recommended. The average number of retrieved MII oocytes was compared between two groups: cycles where the recommendation was the same as the actual physician decision, and cycles where it was different. Ten-fold cross-validation and propensity score matching were performed. Main results and the role of chance The model predicting MII oocyte numbers had an R2 of 0.56 and errors of 3.5 (RMSE), and 2.54 (MAE) overall. For the trigger on the day of the USG examination, it was RMSE: 3.33, MAE: 2.39, and later (+1, +2, +3 days respectively) RMSE: 3.6, 3.67, 3.44, MAE: 2.57, 2.71, 2.56. On average, 1.98 more MII oocytes (95% Confidence Interval: 1.22-2.77) were retrieved from processes where the model recommendation was the same as the actual physician decision (on time) compared to those where the model recommendation differed (not on time). Because this was not a randomized trial, and patient parameters vary across compared groups, propensity matching was used to ensure their homogeneity. After this, there were 1.11 more MII oocytes (CI: 0.22-1.99) retrieved on average in the “on time” group than in the “not on time” group. For patients with less than 10 follicles, there were on average 0.3 more MII oocytes in the “on time” group. For patients with 10-20 follicles, on average 0.72 more MII oocytes were observed, and for those with at least 20 follicles 1.32 more on average. Limitations, reasons for caution The study was limited to a few IVF centers in Poland, and its retrospective findings do not necessarily generalize to different centers. Additional evaluation of the model on data from multiple centers should be performed. Also, randomized control trials could be used to evaluate its effectiveness. Wider implications of the findings Results show the potential of using machine learning to optimize ovarian stimulation outcomes. An increased number of MII oocytes results in a higher success rate of in vitro fertilization. Trial registration number Project support was provided by the Polish National Center for Research and Development no. POIR.01.01.01-00-1634/20-00 and ERC Consolidator Grant TUgbOAT no. 772346.

P-356 Fertility preservation for patients with breast cancer: altered response to ovarian stimulation and loss of cholesterol homeostasis in ovarian follicles

Abstract Study question Does the presence of breast cancer alter the ovarian response to hormonal stimulation and the cholesterol homeostasis in ovarian follicles? Summary answer The deleterious impact of breast cancer on the ovarian response might be link to an alteration of the cholesterol biosynthesis in cumulus cells. What is known already Breast cancer is the most frequent cancer in reproductive-aged women. The cancer itself seems to exert a deleterious impact on the ovarian functions. Indeed, cancer patients who undergo fertility preservation before cancer therapy initiation show a poorer response to ovarian stimulation than healthy women. Nevertheless, this impact remains controversial, and the mechanisms by which the cancer impairs the ovarian functions are poorly understood. To our knowledge, no study has yet evaluated the impact of breast cancer on the cholesterol biosynthesis pathway in human cumulus cells, a pathway essential for oocyte competence to maturation and fertilization. Study design, size, duration 30 patients with breast cancer (10 triple negative (TNBC), 10 hormone-receptor positive (HR+) and 10 HER2 positive (HER2+)) and 30 women oocytes donors undergoing oocyte cryopreservation will be included from January 2019. We assess ovarian response to stimulation (number, quality of retrieved oocytes; total FSH dose). We quantify the level of enzymes and regulators of the cholesterol biosynthesis pathway in cumulus cells (CC) by RT-qPCR. We plan to quantify cholesterol levels in follicular fluids (FF). Participants/materials, setting, methods Since January 2019, 25 breast cancer patients (9 TNBC, 8 HR+ and 8 HER2+) and 30 oocytes donors (control group) under 37 years old have been included. Ovarian stimulation was performed with antagonist protocol. Following ovarian pick up and denudation, CC and FF were collected. After total RNAs extraction from CC, the expression levels of enzymes and regulators of the cholesterol biosynthesis pathway were quantified by RT-qPCR. Cholesterol levels will be quantified in FF. Main results and the role of chance The clinico-biological characteristics (age, BMI) are comparable between cancer patients and the control group (p > 0.05). Serum AMH levels are lower in the TNBC subgroup (2.3±1.6 ng/mL) than in the control group (4.7±2.8 ng/mL, p = 0.04). A poorer ovarian response to ovarian stimulation is observed in the breast cancer group compared with the control group (number of mature oocytes: 9.4±5.2 vs. 14.5±7.7, p = 0.007). Among the cancer patients group, the TNBC subgroup shows the poorest ovarian response to stimulation (number of mature oocytes: 7.6±4.3 vs. 14.5±7.7 in control group, p = 0.006) despite the highest total administered FSH dose (2480±880 IU vs. 1831±460 IU in control group, p = 0.02). Dysregulation of the cholesterol biosynthesis pathway is observed in the breast cancer group. For TNBC and HR+ cancer patients, we observed an increase in the transcripts levels of CYP51 enzyme (respectively 3.28±1.69 vs. 1.84±2.33, p = 0.0098 and 1.77±1.78 vs. 1.84±2.33, p = 0.03) and SREBP2 activator (respectively 2.04±0.95 vs. 1.27±1.13, p = 0.003 and 1.12±0.47 vs. 1.27±1.13, p = 0.02) of the cholesterol biosynthesis pathway compared to the control group. In HER2+ cancer patients, a significant decrease in the expression levels of SQLE (0.39±0.34 vs 1.81±3.99, p = 0.001) and DHRC7 enzymes (0.33±0.32 vs 1.21±0.88, p = 0.0002) is observed compared to the control group. Limitations, reasons for caution Our preliminary results should be confirmed with the analysis of a larger number of participants. We should confirm that the observed modulations in the expression levels of enzymes and regulators of the cholesterol biosynthesis pathway led to a loss of cholesterol homeostasis by quantifying cholesterol in FF. Wider implications of the findings Our findings strengthen the hypothesis that cancer exerts a deleterious impact on the ovarian functions, as we observed a lower ovarian response in patients with breast cancer. This project will have clinical implications, such as to adapt the fertility preservation approach according to the breast cancer subtype. Trial registration number Not applicable

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-793 New approaches for treating diminished ovarian reserve: MSC-derived extracellular vesicles and autologous platelet rich plasma

Abstract Study question Does intraovarian injection of MSC-Derived Extracellular Vesicles (EVs) and autologous platelet rich plasma (PRP) improves the outcome of IVF in women with Diminished Ovarian reserve? Summary answer EVs and PRP therapies increse Antral follicle count (AFC), lower FSH level and result in higher amount of mature oocytes and blastocysts What is known already Diminished ovarian reserve (DOR) and premature ovarian insufficiency (POI) are significant impediments to the success of in vitro fertilization (IVF). Current strategies for ovarian stimulation primarily affects only the growth of antral follicles. Even in scenarios where ovarian ovulatory function is compromised, a reservoir of dormant follicles persists, which could potentially be activated by stem cells. Mesenchymal stem cells (MSCs), owing to their multipotent differentiation capabilities and paracrine signaling properties, have emerged as leading candidates for innovative therapeutic approaches. Recent scientific inquiries have highlighted the paracrine impact of EVs secreted by stem cells, underscoring their prospective therapeutic relevance. Study design, size, duration This prospective interventional study was conducted at the V.I. Kulakov Scientific Research Center for Obstetrics, Gynecology, and Perinatology in Russia. It involved 60 infertile female participants aged 20 to 38 years, each with DOR and a history of at least two unsuccessful IVF cycles. These participants were enrolled in the study during their subsequent IVF cycle. Prior to inclusion, all patients provided written informed consent. Participants/materials, setting, methods Patients in group 1 (n = 30) received treatment with exosomes derived from human umbilical cord mesenchymal stem cells (HUC-MSCs-Exos) prior to initiating their in vitro fertilization (IVF) cycle. In contrast, participants in group 2 (n = 30) underwent intraovarian therapy with autologous platelet-rich plasma (PRP) in preparation for their IVF cycle. The comparative analysis encompassed antral follicle count (AFC), anti-Müllerian hormone (AMH) levels, follicle-stimulating hormone (FSH) levels, ovarian stimulation outcomes, and the primary characteristics of oogenesis and embryogenesis. Main results and the role of chance After transplantation of EVs and PRP the ovarian function-related hormone levels and the AFC returned to nearly normal parameteres.Meanwhile, after exosomal treatment the improvement in reproductive outcomes was more significant. FSH concentration was significantly different before and 30 days after the procedure in both groups. In group 1 FSH values were less than the initial data In 95% of cases, in group 2 – in 72% of cases. AMH levels did not change significantly in both groups. The AFC increased in group 1 compared to group 2. All Patients underwent an IVF antagonist cycle after 3 months from the treatment. The number of obtained oocytes in group 1 ranged from 2 to 8, MII from 1 to 6; in group 2: from 0-5, MII – 0-5. The number of blastocysts in group 1 ranged from 1 to 5, in group 2 – from 0 to 3. In group 1, pregnancy occurred in 9 patients (30%): 1 women ( 3,3%) conceived spontaneously in the cycle of procedures, 8 (26,7%) attempted IVF, in group 2 pregnancy occurred in 4 patients (13,3%): 4 attempted IVF. EVs and PRP injections improve outcomes of IVF results in women with low ovarian reserve. Limitations, reasons for caution Limitations may include the fact that the study is single-center and has a rather small amount of patients enrolled in the study. Fundamental approaches to further research in this area are also required to better understand the obtained results. Wider implications of the findings EVs and PRP therapies appear to enhance ovarian reserve metrics and the success rates of IVF programs in patients with DOR. The clinical implementation of these interventions may offer improved reproductive prospects for patients whose sole option was previously oocyte donation. Trial registration number 121040600410-7

P-124 Machine learning scores reveal mosaic embryo quality as the key predictor for live births, outperforming mosaicism characteristics in ART success

Abstract Study question Is it possible to score the mosaic embryos in order to prioritise them according to their pregnancy potencial? Summary answer The machine-learning score underscores the crucial role of embryo quality over mosaicism, prioritizing high-quality, day-5 biopsied embryos for enhanced live birth outcomes in ART. What is known already After embryo biopsy and PGT-A analysis, embryos can be classified as euploid, aneuploid, or mosaic, wherein a combination of chromosomally normal and altered cells is detected. The transfer of mosaic embryos has been controversial, but currently, the recommendations of international scientific societies, including ESHRE, advocate for their transfer. In case of pregnancy, a prenatal test is advised to rule out any chromosomal aberration. The non-transfer of these embryos reduces ART success chances, as chromosomally normal children may be born from them. Study design, size, duration The study design is observational and retrospective. A total of 8346 embryos from 2583 PGT-A cycles were considered (January-2017 to January-2023). Only transferred mosaic embryos (n = 263) were included in the study. The trophectoderm biopsies of D5, D6, or D7 blastocysts were analyzed by NGS using the Illumina platform (VeriSeq Illumina®, San Diego, CA, USA). The biopsied embryos were vitrified and transferred in a subsequent cycle. Participants/materials, setting, methods The primary indications for PGT-A included advanced maternal age, abnormal sperm FISH, and recurrent miscarriage or implantation failure. Clinical outcomes, along with variables related to progenitors, embryos, biopsy, ovarian stimulation, and adjuvant treatments, were recorded in a database. Machine learning models were conducted using R statistical software (v.4.3.1), and the ‘Caret’ library was utilized to implement different algorithms. ‘Autoscore,’ as an interpretable scoring tool, combined machine learning and regression modeling. Main results and the role of chance The mean maternal and paternal ages were 34.95±6.38 and 39.13±6.74 years. Biopsies were predominantly performed on day 5 (61%). Additionally, 44% of embryos were of A quality, and 49% were of B quality. Regarding clinical outcomes for mosaic embryos, biochemical, clinical pregnancy, and live birth rates were 51%, 41%, and 36%, respectively. The features used to generate the score included those related to embryo quality, biopsy, and mosaicism. Through 10-fold cross-validation, the study identified top-ranking predictors maximizing the AUC of the predictive model. The highest weight in the score was assigned to embryo quality (42%) and day of biopsy (34%), with lower weights for factors related to mosaicism: monosomy and/or trisomy (18%) and mosaicism level (6%). The machine-learning score indicates that, in transferring embryos with mosaicism, priority should be given to high-quality embryos biopsied on day 5. The type and level of mosaicism have a minor impact on the embryo’s gestational capacity, becoming relevant only when prioritizing embryos of identical quality. In such cases, embryos with lower mosaicism degrees and no monosomy demonstrate higher implantation potential. Limitations, reasons for caution The inherent limitations of a retrospective analysis highlight the need for prospective randomized studies to confirm the validity and usefulness of the mosaic embryo transfer score. Wider implications of the findings A scoring system has been developed to prioritize the transfer of mosaic embryos. The crucial variables are associated with embryo quality and the day of biopsy, reflecting the progression of embryonic development. Conversely, variables related to mosaicism play a secondary role. Trial registration number Not applicable

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

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

O-084 Outcomes of female fertility preservation with cryopreservation of oocytes or embryos: a population-based study

Abstract Study question What are the reproductive outcomes observed of patients who cryopreserved oocytes or embryos in the context of fertility preservation in the Netherlands? Summary answer After 10 years follow-up, 25.5% of the women used their cryopreserved oocytes or embryos to attempt pregnancy and of these, 34.6% had a live birth. What is known already Fertility preservation through freezing oocytes or embryos is an established treatment for women with a risk of premature ovarian failure (caused by a benign or oncological disease) or physiological age-related fertility decline. Little is known about the success of freezing protocols, utilization rate of oocytes or embryos and live birth rates. Study design, size, duration A retrospective nationwide observational study was performed in the Netherlands. Data were collected between 2017-2019 from all women who cryopreserved oocytes or embryos more than two years ago in the context of fertility preservation in ten out of twelve IVF centers in the Netherlands. Participants/materials, setting, methods In total 1112 women were included in this study. Medical files and patient databases were used to extract data. The study protocol was approved by the medical ethics committee. Main results and the role of chance Fertility preservation cycles are performed increasingly over the years. In the first years (2004-2007) less than 10 cycles per year were performed, which increased to more than 300 cycles per year in ten years’ time (since 2016). Initially embryos were frozen in the context of fertility preservation. In the later years cryopreservation of oocytes became the standard approach. The median number of oocytes cryopreserved was 13 per woman (range 1-52) and of embryos cryopreserved was 6 (range 1-32). Cryopreservation of oocytes versus embryos resulted in a comparable median number of eligible embryos for transfer (3 and 4 embryos respectively). The 5-year utilization rate was 12.3% and 10-year utilization rate was 25.5%. The cumulative clinical pregnancy rate after embryo transfer of cryopreserved oocytes or embryos was 39.2% and the live birth rate was 34.6% per patient. The return rate of those who had fertility preservation due to benign diseases was higher than for the other indications after five years, namely 17.1% (p < 0.05). After ten years the return rates for the other indications increased to similar percentages for all indications. Limitations, reasons for caution The follow-up period varied between patients and not all cryopreserved material was used yet at the end of this study. This might have led to underestimated pregnancy rates. Further, intention-to-treat analysis could not be performed since women who had a fertility preservation procedure without freezing were not included. Wider implications of the findings This study provides data on the reproductive outcomes after fertility preservation. This knowledge can be informative for professionals and future patients to improve counseling and informed decision making regarding ovarian stimulation in the context of fertility preservation. Trial registration number n/a

P-673 Tubulointerstitial nephritis antigen-like 1 (TINAGL1) expression is lower in the follicular fluid of patients with diminished ovarian reserve (DOR): A novel biomarker

Abstract Study question Are TINAGL1 levels in follicular fluid associated with ovarian reserve in patients undergoing ovarian stimulation for in-vitro fertilization (IVF)? Summary answer TINAGL1 concentration was lower in the follicular fluid (FF) of patients with DOR vs patients without infertility or polycystic ovarian syndrome (PCOS). What is known already TINAGL1 is an extracellular matrix protein involved in cell adhesion, proliferation, migration, and differentiation. TINAGL1 has previously been shown to be expressed in the mouse ovary and to be a serum biomarker that varies throughout the mouse estrous cycle, peaking in the estrous phase. Furthermore, TINAGL1 knockout mice have been shown to be infertile. TINAGL1 expression in the human ovary has not been previously evaluated. Study design, size, duration Between 2019 and 2023, a prospective study of 136 patients undergoing ovarian stimulation and oocyte retrieval (OR) was conducted at a single academic fertility center to assess TINAGL1 levels in luteinized FF and granulosa cells. Study groups were determined by infertility diagnosis: DOR n = 24, polycystic ovary syndrome (PCOS) n = 27, and control n = 85 (undergoing fertility preservation or had a partner with male factor only). Participants/materials, setting, methods TINAGL1 protein levels were quantified in the FF of patients that underwent OR via commercial enzyme-linked immunosorbent assay (ELISA). Granulosa cells were recovered from FF after OR, underwent lysis, RNA extraction, cDNA amplification and TINAGL1 mRNA expression was quantified via quantitative real-time polymerase chain reaction (qPCR). Demographics and infertility diagnoses were collected from the medical record. TINAGL1 levels were compared between the three groups. Statistical analysis was performed with parametric and non-parametric tests as appropriate. Main results and the role of chance Patients with DOR were younger when compared to the control and the PCOS group [Mean(SD) 32.7 (3.8) vs 34.45(3.9) vs 37.7 (3.0) years, p < 0.001] and had lower AMH levels [1.19 (0.8) vs 3.96 (3.03) vs 8.67 (4.56) ng/ml, p < 0.001]. TINAGL1 protein concentration in FF was measured by ELISA. Mean (SD) TINAGL1 levels were highest in PCOS, and lowest in the DOR group. Mean TINAGL1 levels were higher in the FF of the PCOS group when compared to the control group [4.73(7.15) vs 4.45 (4.57) ng/ml, p = 0.83] but this difference did not reach statistical significance. However, mean TINAGL1 FF levels were significantly lower in the DOR group when compared to the control group [2.54 (1.6) vs 4.48 (4.57) ng/ml, p = 0.04]. TINAGL1 was also found to be expressed in the granulosa cells with qPCR. TINAGL1 expression was upregulated by (+89%) in the PCOS group vs the control group (p = 0.0095). Importantly, there was a trend for decreased (-52%) TINAGL1 expression in DOR when compared to the control group (p = 0.67). The latter result should be interpreted with caution since only a subset of samples had sufficient granulosa cells for RNA extraction (DOR=4, control=18, PCOS=5). Limitations, reasons for caution This is a single institution study with a small number of patients in the DOR group (n = 24). Wider implications of the findings This is the first study to show that TINAGL1 is expressed in human granulosa cells. Decreased TINAGL1 may be a biomarker associated with DOR. Future studies should assess serum TINAGL1 levels at baseline and during ovarian stimulation and its contribution to the pathophysiology of DOR. Trial registration number Not applicable

O-234 Indication for fertility preservation in patients with endometriosis

Abstract Endometriosis is a complex gynecological condition that not only causes debilitating symptoms but also significantly impacts fertility. As the disease affects approximately 10% of women of reproductive age, addressing fertility preservation strategies becomes paramount. The conventional treatments for endometriosis, such as medical therapy and surgery, often fail to fully address its adverse effects on ovarian reserve and reproductive potential. Consequently, there is a growing interest in exploring fertility preservation options, particularly oocyte cryopreservation (OOC), for endometriosis patients. Despite the prevalence and impact of endometriosis on fertility, comprehensive data and guidelines specifically tailored to fertility preservation in this population remain scarce. The available evidence suggests that endometriosis, particularly when it involves ovarian endometriomas, is associated with a significant reduction in ovarian reserve, as indicated by lower levels of anti-Müllerian hormone (AMH). Surgical interventions, often necessary for managing endometriosis-related complications, can further compromise ovarian function and diminish fertility prospects. However, recent studies have shed light on the potential benefits of OOC in preserving fertility for endometriosis patients. OOC offers a minimally invasive approach with no impact on ovarian reserve compared to other fertility preservation techniques. Despite the lack of randomized controlled trials, our retrospective data have demonstrated promising outcomes, with a notable number needed to treat (NNT) of 16 for one successful pregnancy. This underscores the significance of discussing and considering OOC as part of the treatment plan for endometriosis patients, especially those at risk of ovarian compromise due to the disease or its management. The decision to pursue fertility preservation through OOC should be made on a case-by-case basis, taking into account various factors such as disease severity, patient age, ovarian reserve, and treatment history. French guidelines recommend considering OOC for endometriosis patients with bilateral ovarian endometriomas larger than 3 cm or those with endometriomas on a single ovary. Initiating fertility preservation discussions early, preferably before surgical intervention, allows patients to make informed decisions regarding their reproductive future. It is crucial to acknowledge the challenges and uncertainties associated with fertility preservation in endometriosis patients. Socio-economic factors, patient preferences, and the lack of clear criteria for selecting candidates for OOC pose significant hurdles. Furthermore, the effectiveness and cost-effectiveness of OOC in this population warrant further investigation. In addition to OOC, alternative fertility preservation options, such as ovarian tissue preservation, could be considered, particularly in cases where ovarian stimulation is not feasible or declined by the patient. However, data on the efficacy and safety of ovarian tissue preservation specifically in endometriosis patients are limited, highlighting the need for further research in this area. In conclusion, fertility preservation, particularly through OOC, holds promise for mitigating the adverse effects of endometriosis on ovarian function and fertility. While uncertainties persist, integrating fertility preservation discussions into the comprehensive management of endometriosis is essential. This ensures that patients are empowered to make informed decisions about their reproductive health and maximizes their chances of achieving desired fertility outcomes despite the challenges posed by endometriosis.