Oocyte Maturation Research Articles

P-506 Oocyte/zygote/embryo maturation arrest: a functional and clinical study expanding the phenotype of NOBOX variants

Abstract Study question Are pathogenic NOBOX variants causal for oocyte/zygote/embryo maturation arrest (OZEMA) and what is their molecular mechanism? Summary answer Expression analysis of NOBOX target genes indicates that the examined variants do not influence early folliculogenesis, suggesting a potential involvement in later developmental stages. What is known already Primary ovarian insufficiency (POI) affects around 1% of women under 40 with pathogenic variants in the transcription factor NOBOX being causal in 5-7% of cases. Historically, NOBOX has been linked to premature oocyte depletion. Functional studies in female Nobox knockout (-/-) mice reveal a substantial disruption in germ cell cyst breakdown. This disruption impairs the formation of primordial follicles and the subsequent transition from primordial to primary stages, leading to the early loss of all oocytes. Study design, size, duration Three OZEMA families are presented with two distinct NOBOX variants. A functional study is conducted to explore alterations in mRNA expression associated with the investigated NOBOX variants. Participants/materials, setting, methods Three infertile women with OZEMA underwent multiple in vitro fertilization cycles. Subsequent, exome analysis targeting fertility-related genes revealed the presence of distinct NOBOX variants. To assess their impact on NOBOX target gene expression, we generated mutant NOBOX expressing plasmids via site-directed mutagenesis and transfected them into HEK293T cells. The expression of known NOBOX target genes was monitored by RT-qPCR. Main results and the role of chance We examined three families affected by OZEMA, in which the affected women were heterozygous for NOBOX variants. In one family, we found a heterozygous paternally inherited NM_001080413.3(NOBOX): c.1797_1798delCT, p.(Arg600Aspfs*6) variant in a female with oocyte maturation arrest. In two other families, a heterozygous probably pathogenic paternally inherited NM_001080413.3(NOBOX): c.1849C>T, p.(His617Tyr) variant was detected in females experiencing embryo maturation arrest. Analysis of NOBOX target genes in HEK293T cells revealed that both variants had no impact on the mRNA expression of MOS and OCT4, both of which are implicated in early folliculogenisis. Since both MOS and OCT4 are implicated in earlier folliculogenesis stages, this supports that NOBOX might also be implicated in later stages. Contrastingly, a known pathogenic NOBOX variant, used as a positive control, showed decreased MOS and OCT4 expression. Limitations, reasons for caution Verification of our findings is necessary, given that this is the first report of NOBOX variants in individuals with OZEMA. The precise molecular mechanism underlying OZEMA remains undisclosed at this stage. These results warrant the need of genome-wide mRNASeq to confirm and expand our findings. Wider implications of the findings Since NOBOX pathogenic variants are typically linked to POI, our findings suggest a broader clinical impact, where NOBOX plays a role in oocyte maturation and early embryo development. Hence, the investigation of NOBOX variants is advisable for individuals diagnosed with OZEMA. Trial registration number Not applicable

O-043 Con

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

P-620 Oocyte competence in Vitro Fertilization: relation between serum anti-Müllerian hormone (AMH) concentrations and complement C4 protein expression in follicular fluid

Abstract Study question To investigate if serum AMH concentration variations are correlated with protein expression in follicular microenvironment affecting IVF outcomes. Summary answer Serum AMH concentrations were associated with altered levels of intrafollicular protein involvement of the complement pathway in immunity response in follicular fluid (FF). What is known already Anti-Müllerian hormone (AMH) plays a crucial role in regulating growth and development of ovarian follicles. The follicular fluid is produced during folliculogenesis and contains a variety of proteins that play important roles in follicle development and oocyte maturation. AMH concentration in follicular fluid can be a marker of ovarian reserve status and oocyte competence. AMH elevated levels may indicate a higher ovarian reserve and are sometimes associated with a greater ovarian response to ovarian stimulation used in IVF. However, the exact relationship between AMH levels in follicular fluid and IVF outcomes may vary among women and depend on various factors. Study design, size, duration The study included FF collected from 75 patients underwent IVF from December 2018 to June 2019.All patients enrolled underwent GnRH antagonist stimulation protocol with r-FSH according to clinical/ovarian features.Patients were sorted into three groups according to serum AMH concentrations: AMH≤1.0 ng/ml, n = 25 (A group); AMH=1.1-2.0 ng/ml, n = 29 (B Group); AMH>2.0 ng/ml, n = 21 (C group).Cutoffs for defining low(A), average(B), and high(C) AMH serum concentrations corresponded to round values of 30th and 70th centiles of each measurement. Participants/materials, setting, methods Exclusion criteria: endometriosis, metabolic/endocrinology diseases and oligoasthenoteratozoospermia. FF aspirates from individual follicles (diameter ≥18 mm) were collected on the day of oocyte retrieval. The FF was analyzed by two-dimensional gel electrophoresis (2-DE). Oocyte number and quality, fertilization rate are IVF outcome measures. Data were analyzed using the unpaired Student’s t-test by IBM SPSS-STATISTICS versions 20.0 and considered significant if p-value ≤ 0.05. Main results and the role of chance 180 protein spots were highlighted in three groups: 80% is represented in all the samples analyzed, whereas 19 protein spots out of 180 are group-specific. Five unique upregulated proteins were identified in the A group and five in C group respect to control group (B). These were identified IG, CO4, ALBU, TRFE, IGLC in A group, while A1AT, ANT3 A2HS, HPT and CO4 in C group. A and C group showed worse oocyte quality associated with a lower fertilization rate than B group. On the basis of the proteome analysis, the component of the complement cascade C4 was found more plentiful in patient with low and high AMH serum concentration compared to average AMH serum concentration ones. The presence of high levels of the unprocessed precursor C4 correlated to serum AMH fluctuations is an indication of non-activation of the complement pathways fundamental for follicle maturation and ovulation compromising IVF outcome. Limitations, reasons for caution Limited number of patients. Age and lifestyle factors (i.e. smoking, diet) are not considered. Wider implications of the findings Results showed an increase of CO4 in FF of patients with low and high AMH serum concentrations. CO4 FF high levels could be indicative of defective complement activation during ovulation with consequent impaired processes and lower standard oocyte competence. Thus, CO4 could be identify as biomarker to predict IVF success. Trial registration number Not Applicable

P-027 Sperm motility and calcium ionophore treatment influence fertilization and pregnancy outcomes in TESE-ICSI

Abstract Study question Are there differences in fertilization and pregnancy rates post-TESE-ICSI between motile and immotile sperm, and do these vary in treatments with and without calcium ionophore? Summary answer Post-TESE-ICSI data reveals differences in fertilization and pregnancy rates when comparing motile vs. immotile sperm and treatments with and without calcium ionophore after TESE-ICSI. What is known already Testicular sperm extraction (TESE) followed by intracytoplasmic sperm injection (ICSI) poses a challenge for every IVF laboratory. This is particularly true in patients exhibiting azoospermia, where only a few and mostly immotile sperm are present in testicular tissue. In these cases, a calcium ionophore treatment for activation of the oocyte may help to overcome poor prognosis fertilization outcome, and thereby enhancing the likelihood to achieve a transfer leading to a successful pregnancy. Although both techniques, TESE-ICSI and activating substances are commonly applied, detailed analyses for individual counselling of couples are missing. Study design, size, duration This study analyzed 787 TESE-ICSI cycles (2015-2023) regarding patient age, number of attempts, oocyte maturity, fertilization and pregnancy rate after fresh embryo transfer. Cycles were split into four groups: (A) at least one motile sperm was injected (n = 493); (B) only immotile sperm were used (n = 294); (C) calcium ionophore (n = 474); (D) no calcium ionophore (n = 313). 17 cycles were excluded from the study because no sperm were found on the day of TESE-ICSI and oocytes were vitrified. Participants/materials, setting, methods In our IVF clinic, calcium ionophore treatments are only offered if a pre-screening of TESE samples reveals the absence of motile spermatozoa or if a previously conducted TESE-ICSI attempt resulted in a low fertilization rate (<30%) or a total fertilization failure. Statistical analyses was performed to compare the motile and immotile sperm group and the groups with or without calcium ionophore treatment. Main results and the role of chance No differences were found in all groups (A-D) regarding age of female or male patient and number of collected oocytes per group. However, our results demonstrate a difference in the mean number of ICSI attempts when comparing motile sperm and immotile sperm (2.0±1.3 vs. 2.3±1.6, p < 0.05), and when comparing attempts with calcium ionophore treatment and those without (2.4±1.6 vs. 1.8±1.8, p < 0.0005). The mean fertilization rate (2PN stage) was higher in the motile sperm group (A) compared to the immotile group (B) (57.8% vs. 28.4%, p < 0.0005) and also higher in attempts of group (D) in comparison to attempts of group C (56.8% vs. 40.2%, p < 0.0005). While fertilization failure occurred less often in group (A) (3.2%) it occurred to a higher rate in group (B) (19.4%), followed by group (C) (12.0%). Biochemical (BPR) and clinical pregnancy rates (CPR) showed a significant difference between the motile and immotile sperm group (BCR: 33.2% vs. 12.3%, p < 0.0005; CPR: 25.6% vs. 9.3%, p < 0.0005), but no differences between the two calcium ionophore groups. Limitations, reasons for caution This analysis was done retrospectively. A potential subgroup analysis of groups (A) and (B) into calcium ionophore use and of groups (C) and (D) into motile or immotile sperm will reveal the effect of calcium ionophore on success rates regardless of sperm motility. Wider implications of the findings Our data provides insight into success rates of TESE-ICSI cycles, especially if only immotile sperm were present. This will serve as a helpful guide for physicians when counseling patients about their success rates and to optimize the outcome in cases with poor prognosis by using a calcium ionophore treatment. Trial registration number not applicable

P-367 Letrozole or Tamoxifen co-administration during fertility preservation of breast cancer patients: a retrospective cohort study

Abstract Study question How do fertility preservation (FP) outcomes differ between breast cancer patients stimulated with FSH and Tamoxifen versus FSH and Letrozole? Summary answer Letrozole and Tamoxifen co-administration yielded similar number of retrieved and cryopreserved oocytes/embryos, as well as similar oocyte maturation and fertilization and rates. What is known already Oocyte/embryo cryopreservation is recommended before initiation of chemotherapy in cancer patients. The co-administration of Tamoxifen, a selective estrogen receptor modulator, or Letrozole, an aromatase inhibitor, during ovarian stimulation with gonadotropins, are used to limit the potentially harmful effects of a supra-physiological rise in estrogen levels on hormone-sensitive cancers. However, the optimal choice between the two is still unclear and with no sound evidence. Study design, size, duration Retrospective cohort study of all FP treatments of newly diagnosed breast cancer patients in two tertiary centers between 2000-2022. Collected data included 354 FP cycles of 290 patients and compared treatment parameters and outcomes of Tamoxifen or Letrozole co-administration. Participants/materials, setting, methods Breast cancer patients who underwent FP before chemotherapy were included. Patients with a history of radiation or gonadotoxic treatment, as well as those undergoing other fertility preservation treatments, such as ovarian tissue cryopreservation were excluded. Main results and the role of chance Overall, 215 Letrozole and 139 Tamoxifen treatment cycles were compared, with no significant demographic differences. Treatments with Letrozole had higher FSH dosages (3970IU vs. 2839IU, p < 0.001) but shorter duration (9.7 vs. 10.5 days, p < 0.001). The Letrozole group achieved lower peak E2 levels and endometrial thickness (1508pmol/L, 8.1mm vs. 8760pmol/L, 9.5mm, p < 0.001). The mean number of retrieved oocytes was comparable between the groups (13.6 with Letrozole vs 14.7 with Tamoxifen, p = 0.06). In 122 Letrozole and 46 Tamoxifen patients that underwent strictly oocytes cryopreservation the mean number of cryopreserved oocytes was comparable (11 vs. 12.1, p = 0.21). Moreover, in embryo cryopreservation cycles of 71 patients treated with Letrozole compared to 76 patients with Tamoxifen, no difference was observed in the number of cryopreserved embryos (6.2 vs. 7.0, p = 0.12). Oocyte maturation rate among strictly oocyte preservation cycles was comparable (86% with Letrozole vs. 83% with Tamoxifen, p = 0.80), as were fertilization rates in embryo cryopreservation cycles (62% vs. 63%, p = 0.8 and 71% vs. 76%, p = 0.3 in IVF and ICSI with Letrozole and Tamoxifen, respectively). Multivariate analysis, controlling for potential confounders showed no significant correlations between Tamoxifen or Letrozole co-administration and the number of retrieved oocytes or oocyte maturation rate. Limitations, reasons for caution The primary limitation of our study is its retrospective design and the variation in treatment duration and gonadotrophin dosages among groups. Wider implications of the findings This study provides reassurance that both Tamoxifen and Letrozole are equally effective options when co-administered in FP treatments of breast cancer patients. Trial registration number not applicable

P-014 Extracellular vesicles (EVs) from female reproductive tracts positively affect sperm capacitation and progressive motility

Abstract Study question Do EVs from human follicular fluid (FF-EVs), cervicovaginal fluid (CVF-EVs), and endometrial stromal cells spent medium (ESCs-EVs) induce sperm capacitation and enhance sperm motility? Summary answer In humans, EVs from different female reproductive tracts actively contribute to sperm maturation by inducing capacitation and enhancing sperm progressive motility. What is known already In the human body, EVs represent crucial players in cell-to-cell communication. EVs presence has been detected also in the female and male reproductive systems, specifically in seminal, follicular, oviductal, endometrial and vaginal fluid, as well as in embryo secretions. Moreover, EVs have been shown to be of pivotal importance in the fertilization process, as they support the maturation of spermatozoa and oocytes, as well as embryos in their development and endometrial implantation. The majority of these studies, though, have been conducted in animal models, underscoring the necessity to replicate analogous investigations also in humans. Study design, size, duration Follicular fluid (FF, n = 8), cervicovaginal fluid (CVF, n = 20) and endometrial tissue (n = 8) samples were collected from women undergoing assisted reproductive technology (ART) cycles at San Raffaele Hospital Fertility Centre (Milan). CVF were collected 2 and 7 days after the LH peak (CVF LH + 2 and CVF LH + 7, respectively). ESCs-EVs were isolated from both decidualized (dESCs-EVs) and not decidualized (eESCs-EVs) endometrial cells. Semen samples (n = 15) were collected from normozoospermic men. Participants/materials, setting, methods EVs were isolated using differential centrifugations and characterized using Transmission Electron Microscopy (TEM), Nanoparticle Tracking Analysis (NTA), and western blotting (WB). EVs capture by spermatozoa was assessed using flow cytometry. EVs impact on sperm progressive motility was evaluated following WHO guidelines. EVs potential to induce sperm capacitation was examined through sperm acrosome reaction (AR) induction using a Ca2+ ionophore, followed by Coomassie blue staining. All experiments were performed using EVs at 50 and 100 μg/mL. Main results and the role of chance Isolated EVs displayed comparable size, with mean diameters ranging from 147,9±11,6 nm to 168,1±6,2 nm (mean ± SEM) and average concentrations from 9,53E+10 ± 8,11E+09 to 2,70E+11 ± 3,49E+10 particles/ml (mean ± SEM). TEM analysis confirmed their round-shaped morphology and structural integrity, while WB confirmed their positivity for EVs markers (Alix, TSG101, CD63, CD9). Spermatozoa efficiency in capturing these fluorescently-labeled EVs, measured as the percentage of fluorescence-positive spermatozoa, reached up to 3,6±1,1% for FF-EVs, 12,1±3,7% for CVF-EVs and 9,4±1,9% for ESCs-EVs (mean ± SEM). Sperm cells co-incubated with any EVs group maintained unaffected vitality. Following a 4-hour incubation with EVs, a rise in the proportion of progressively motile spermatozoa was observed, with percentages of progressively motile spermatozoa ranging from a minimum of 45,4±3,8% for CVF-EVs LH + 7 to a maximum of 52,7±2,7% for dESCs-EVs (mean ± SEM). This increase resulted to be statistically significant (p < 0.05 and p < 0.01, respectively) compared to the untreated (UT) condition, which exhibited 26,2±0,7% of progressively motile sperm cells. Spermatozoa that completed the AR, indicating capacitation, after 4-hour incubation with EVs resulted to be up to 25,8±3,2% for FF-EVs, 35,0±6,6% for CVF-EVs and 26,9±3,0% for ESCs-EVs, compared to an average of 13% in the UT control. Limitations, reasons for caution This study constitutes a pilot investigation characterized by a limited sample size, necessitating larger cohorts to validate results. Wider implications of the findings Studied EVs may exert beneficial effects on capacitation and progressive motility also on asthenozoospermic (AS) men’s spermatozoa. Therefore, they could be used in ART cycles to prime spermatozoa from AS men and increase the percentage of sperm cells displaying progressive motility, potentially favouring fertilization via classical IVF instead of ICSI. Trial registration number not applicable

P-223 Follicular fluid from women stimulated with hMG protocol displays altered energy metabolism and this impacts embryo morphokinetics

Abstract Study question Does different type of ovarian stimulation affect follicle metabolism? Summary answer Patients stimulated hMG-only show increased levels of glucose and MDA in follicular fluid and longer Cc3 embryo time compared to patients stimulated rFSH and hMG. What is known already Oocyte growth and maturation strongly rely on energy metabolism. However, there is a notable lack of studies examining the influence of ovarian stimulation protocols on individual follicular fluid. While certain studies indicate changes in genes associated with glucose metabolism in patients subjected to different protocols, there remains a need for prospective studies in this field. Study design, size, duration This is a single-center prospective analysis from March 2022 to August 2022 including 20 patients. From the total, 14 were stimulated with rFSH + hMG and 6 with hMG only. A total of 81 embryos were submitted to morphokinetics analysis. Patients with Polycystic Ovary Syndrome (PCOS), Ovarian insufficiency, Endometriosis in stages III and IV, and patients who have already undergone other attempts at the clinic were excluded. Participants/materials, setting, methods Patients were firstly assessed by age, body mass index (BMI), and dosage of stimulation hormones. Puncture of follicles was performed individually after system wash and only follicular fluid (FF) with no visible blood contamination were submitted for analysis. FFs were analyzed for glucose, lactate, insulin (specific fluorometric assays), and MDA (important oxidative stress marker). Morphokinetics analyses were performed for all available embryos from day 0 until day 6. Main results and the role of chance Body Mass Index (BMI) and ages were similar among the categories (p = 0.388 and p = 0.373, respectively). FSH dosage used in both groups was not different (p = 0.85) but LH used was higher in patients treated with human menopausal gonadotropin (hMG) (p = 0.002). Women whose treatment was hMG presented more glucose in FF (p = 0.02) and MDA (p = 0.02) while no differences were observed for insulin and lactate content (p = 0.57 and p = 0.72 respectively). There was a significant increase of 3º Cell Cicle (Cc3) time of embryos from women treated with hMG only. Taken together, these data suggest that hMG is modifying the glucose metabolism by interrupting glycolysis in the oocyte, resulting in a higher amount in FF, which increases Malondialdehyde (MDA) levels. Considering that oocytes from women treated with hMG only had an altered metabolic profile, this could impact the further embryo development, with consequences specifically at the time of the embryonic metabolic shift. Limitations, reasons for caution The limited number of patients is a limitation of the study and the lack of standardization in the use of trigger, despite of not having significant difference. Wider implications of the findings Understanding the implication of hormones in follicular microambient might help individualization of hormones usage and improve the outcomes of IVF treatment. Trial registration number 44895621.1.0000.5594

P-664 Insulin-like peptide 3 as a potential biomarker in predicting IVF success and ovarian reserve in women with unexplained infertility and diminishing ovarian reserve

Abstract Study question Could insulin-like peptide 3 (INSL3) predict ovarian reserve and in vitro fertilization (IVF) success in women with unexplained infertility (UI) and diminishing ovarian reserve (DOR)? Summary answer In women with DOR, reduced intrafollicular and serum INSL3 levels correspond with low AMH and high FSH levels, similar to established ovarian reserve markers. What is known already INSL3, belonging to the insulin-like peptide family, is produced by theca interna cells within antral follicles and the corpora lutea. It is hypothesized that INSL3 is integral to the initial development and function of antral follicles, specifically through its regulatory effect on androgen biosynthesis in the thecal cells of these follicles. Moreover, INSL3 is implicated in the modulation of the ovarian microenvironment, which is essential for facilitating the maturation of oocytes. Study design, size, duration This research was carried out at the IVF centers of two tertiary university hospitals, assessing 49 infertile women with either UI (n = 24) or DOR (n = 25) during IVF treatment. A control group (n = 26) comprised women with normal ovarian reserve undergoing IVF due to male or tubal factors. Outcome parameters are ovarian reserve markers (serum FSH, estradiol, AMH, INSL3 concentration and antral follicle count [AFC]), positive pregnancy rate and live birth rate (LBR) (gestational age ≥28 weeks). Participants/materials, setting, methods Women aged between 20-40 with a body mass index (BMI)<30 kg/m² were included. Serum FSH, estradiol, AMH, INSL3 levels and AFC were evaluated on menstrual cycle days 2 or 3, and INSL3 in follicular fluid from dominant follicles (>14 mm) were evaluated during oocyte retrieval. Exclusions included endocrine abnormalities (e.g., polycystic ovary syndrome, hyperprolactinemia, hypo and hyperthyroidism) cycle cancellation due to lack of a viable embryo, uncorrected Mullerian anomalies, recurrent miscarriage history and hydrosalpinx presence. Main results and the role of chance The mean age in the study groups was 28.41±3.5 (UI), 32.40±4.21 (DOR), and 29.65±3.91 (control). In the DOR group, female age (p = 0.001), BMI (p = 0.049), duration of infertility (p = 0.006), previous IVF attempts (p < 0.001), basal FSH (p < 0.001), and basal estradiol (p < 0.001) were higher, while AMH (p < 0.001), AFC (p < 0.001), and follicular fluid INSL3 (p < 0.001) were lower. Serum INSL3 in DOR was lower but not statistically significant. No correlation was found between serum INLS, follicular fluid INSL3, ovarian reserve markers, positive pregnancy rates, miscarriage, and LBR. DOR group had longer stimulation durations (p = 0.017), but lower max estradiol (p < 0.001), fewer oocytes (p < 0.001), mature follicles (p < 0.001), and PN (p < 0.001). Pregnancy rates were 54.1% (UI), 24% (DOR), and 53.84% (control); LBRs were 54.1% (UI), 20% (DOR), and 42.3% (control), with significant differences in pregnancy tests (p = 0.04) and LBR (p = 0.03), both lower in DOR. Univariate analysis identified duration of infertility (p = 0.019) and basal FSH (p = 0.009) as significant LBR predictors. Multivariable analysis confirmed basal FSH (p = 0.033) as significant, with increased duration of infertility and basal FSH level reducing LBR probability. Limitations, reasons for caution The limited sample size of our study potentially undermines the robustness of circulating INSL3 as a predictive biomarker for DOR, evidenced by the non-significant decrease in serum INSL3 levels in the DOR group. Moreover, the lack of INSL3 level assessment during oocyte retrieval further constrains our findings. Wider implications of the findings Our research explored INSL3 as a viable biomarker for predicting ovarian reserve and IVF success in UI and DOR cases. Reduced INSL3 levels in circulation and follicular fluid in DOR patients could be beneficial in clinical practice. Trial registration number not applicable

O-061 Ovarian cancer and fertility - current understanding

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

P-771 Does follicle size impact effect of follicular flushing on oocyte retrieval rate and embryology outcomes?

Abstract Study question Is the effect of follicular flushing on oocyte retrieval rate (RR) and embryology outcome influenced by follicular size? Summary answer Flushing improved RR in discordant growth with smaller(8-12 mm) follicles and larger(>22mm) follicle. Flushing did not impact embryological outcomes adversely. It increased top quality embryo What is known already Follicular flushing is done in poor responder for improving retrieval rate. There are very few studies in normal or hyper responders. Studies show controversial results of flushing, some showing benefits, while others, a detrimental effect because of increased intra-follicular pressure, increased procedure time, and change in paracrine milieu of oocytes by dilution with flushing medium No study has addressed whether increased retrieval rates with flushing are dependent on follicular size and indirectly maturity of oocyte. Most studies flushed with fixed volume of 1-2ml as size of follicle was not taken into account, making volume inadequate for completely flushing larger follicles. Study design, size, duration Prospective cohort study conducted from September 2022 to August 2023. Group 1: Study group- follicles were flushed after aspiration. Total patients were 120. They were divided into 3 groups according to follicular size and fluid volume aspirated with sample size calculated as A:306 small follicles 8-12 mm(<1.0ml), B:467 medium follicles 13-22 mm (1.0-6.0ml) C:102 large follicle > 22 mm (>6.0 ml). Group 2- Control group where follicles aspirated without flushing in 280 patients, 2572 follicles. Participants/materials, setting, methods Ethical approval taken. Inclusion - patients 21-40years of age undergoing oocyte retrieval for IVF/ICSI cycle with antagonist protocol Exclusion of oocyte of indeterminate origin ie one aspirate have two oocytes Group1 After aspiration of follicle with double lumen oocyte retrieval needle, follicle flushed with media volume equivalent to follicular volume. Group2 only follicular aspiration and volume measured Analysis done using SPSS-25 version. Primary outcome retrieval rate(RR) of oocytes. Secondary outcome: fertilization rate, percentage of top quality embryos(TQE)on day3&5, blastocyst rate. Main results and the role of chance Flushing follicle significantly increased RR in smaller follicles(8-12mm) compared to controls 159/311 (51.12%)vs 176/780 (22.56%) p = <0.001 and also in larger follicles(>6ml) 76/109 (69.72%)vs 116/219 (52.96%) p = <0.01 No difference seen in optimum size follicles (13-22mm) 337/470 (71.7%)vs 1099/1573(69.86%) p = 0.44. Overall, there was statistically significant increase in RR with flushing 567/890 (63.7%)vs 1391/2572 (54.08%) p = <0.001. Significantly more time was taken for flushing vs control groups 16.50vs 12.15 minutes p = <0.001. Secondary outcomes like fertilization rate was not different with flushing 476/567 (83.95±15.01%)vs 1125/1391(80.88±19.01 %) p = 0.21. Percentage of TQE (day 3) were significantly more in flushing group 321/476 (67.43±25.41%)vs control 642/1125 (57.07±25.94%)p = <0.01. TQE (day 5) were significantly more in flushing group 142/476 (29.83±11.02)vs control 251/1125 (22.31±12.11%)p=0.04. Blastocyst rate remained similar in both groups 196/476 (41.18±16.73 %) vs 403/1125 ( 35.82±13.90 %) p = 0.12. Subgroup analysis showed that younger women (<35yrs)had a significantly higher RR with flushing 66.33±16.29%vs controls 57.88±13.68% (p = <0.01), compared to older women >35 years 60.29±16.37%vs 56.35±17.30% (p = 0.38). Women with higher AMH had better RR with flushing 63.71±15.11%vs controls 56.50±14.33 (p = 0.01) compared to women with lower AMH (<1 ng/ml) where flushing made no difference 63.47±19.59%vs 60.62±14.93(p = 0.79). Normal and hyper responders had significantly higher RR with flushing 66.16±15.11vs controls 57.53±13.85%(p = <0.001) compared to poor responders (<5 oocytes) 51.07±18.07vs 56.24±27.47(p = 0.55). Limitations, reasons for caution Although RR was better with flushing in small and large follicles we could not translate the advantage to pregnancy rate(PR) PR could not be calculated as some patients wanted 2 embryos transferred. Since patient had one each embryos from small and optimum follicles both were transferred. Further RCT required. Wider implications of the findings Practice of follicular flushing needs re-evaluation Women with discordant growth should be taken for flushing as it increases RR in small and large follicles Role of flushing should be widened beyond poor responders to younger women, with normal or hyper response increasing oocyte yield which may increase cumulative pregnancy rate Trial registration number not applicable

O-003 COC classifier: a new artificial intelligence-based tool for identifying mature oocytes from cumulus- oocyte-complexes

Abstract Study question Can the use of artificial intelligence (AI) enhance the prediction of mature oocytes (MII) from Cumulus-Oocytes-Complexes (COC) significantly surpassing the accuracy of well-trained embryologists? Summary answer The development of a COC classifier, an AI-based tool, improves the prediction of mature oocytes from COCs graded as 3 and 4 before oocyte denudation. What is known already Determining the maturity of Metaphase II oocytes before denudation is a challenge in assisted reproduction due to the presence of a dense cumulus mass surrounding the oocyte and obstructing proper manual scoring, a critical step in intracytoplasmic sperm injection (ICSI) due to risk of granulosa cells removal from immature oocytes. Although there is a certain correlation between COC morphology and nuclear oocyte maturity, it is not 100% accurate. It is reported that approximately 90% of MII oocytes are expected in expanded COCs (grade 1), while in COCs grade 4, more immature oocytes are predicted and only 25% are MII oocytes. Study design, size, duration 931 COC's from 145 patients were submitted to COC grading by both, manual and a new “COC classifier” from October to January 2023. 4 groups were formed according to Ebner criteria, 2008. Grade 1: 192 COC's (suspected mature), fluffy and radiant corona and cumulus; Grade 2: 318 COC's showing fluffy cumulus (suspected mature); Grade 3: 208 COC's with radiant corona (expected mature) and grade 4: 213 COC's (suspected immature) with dense cumulus without visible oocyte. Participants/materials, setting, methods Prospective study included 145 patients (39.3 years ±3.2) from September to December 2023. After COC obtention, excess of granulosa cells, dark and blood cells were removed. 3 hours after egg collection, COCs were photographed and scored manually by 9 well trained embryologists. Before denudation, obtained COCs were classified in 4 morphological stages according to Ebner et al, 2008. Finally, the taken photos from COC's were analysed by the COC classifier, a sypervised deep learning algorithm. Main results and the role of chance After COC's classification as following: Group 1 (suspected mature), fluffy and radiant corona and cumulus with visible oocyte; Group 2, COC's showing dense corona (oocyte clearly visible) but fluffy cumulus (suspected mature); Group 3, COC's with radiant corona (oocyte visible, expected mature); Group 4, COC's (suspected immature) with dense corona and cumulus without visible oocyte. The new software presented an MII oocyte accuracy of 79.16% for group 1, 87.1% for group 2, 83.17% for group 3, and 73.23% for group 4. In comparison, manual COCs grading by nine experienced embryologists yielded accuracy rates of 73.5% MII oocytes in group 1, 79.5% for group 2, 50.3% for group 3, and 46.9% for group 4. Statistical analysis, using the chi-square test, was performed to compare the accuracy rates between the COC classifier and manual grading. The results revealed significant differences in favor of the COC classifier when compared to manual method for the groups 3 and 4 (p < 0.001). These results indicate a superior performance of the COC classifier in predicting MII oocytes for groups with highest rates of inmture oocytes. However, for groups 1 and 2, there were no statistically significant differences between the COC classifier and manual grading. Limitations, reasons for caution Further validation through a large-scale, prospective, randomized study is necessary to confirm the efficacy and reliability of the new COC classifier, particularly in patients with oocyte cohorts enriched with grade 3 and 4 COCs. Ongoing research is currently being conducted in our laboratory. Wider implications of the findings The new COC classifier, an AI-based tool, developed by our group, offers a non-invasive and efficient method in predicting mature oocytes before denudation by identifying more MII oocytes from patients’ cohorts enriched with grade 3 and 4 COC's, postponing denudation and injection timing or destinating them to conventional IVF Trial registration number 5678765

O-071 Stringent statistical analysis of 108,684 oocyte donation cycles identifies 2.6% of donors with specific oocyte/embryo developmental arrest phenotypes for genome association studies

Abstract Study question Can statistical modelling accurately identify an outlier group of presumed fertile donors with specific reduced embryological outcomes suggestive of an underlying infertility-related genomic condition? Summary answer Statistical modelling identified a highly specific group of donors as embryologically under-performing outliers across multiple treatment cycles for the optimisation of downstream genomic association studies. What is known already Female infertility has a wide range of clinical presentations. While some causes of infertility are well defined, the aetiology of most infertility remains unexplained. Since IVF allows for in vitro monitoring of oocyte and embryo, it is now possible to identify subtle infertility endophenotypes, characterized by specific developmental failure that would otherwise go undetected in natural conception. Currently, the lack of large and well-categorized datasets of infertility endophenotypes has limited research in the area. Therefore, a clear and methodological definition of infertility endophenotypes in IVF is the first crucial step towards a better understanding of their mechanism and biological/genetic aetiology. Study design, size, duration A retrospective analysis was performed on clinical and embryological data from 40497 egg donors, undergoing 108.684 stimulations, with 4.235.036 oocytes retrieved. The data also included information on the 85482 recipients and their 190996 oocyte reception cycles, spanning from 1999 to 2023. Infertility endophenotypes were able to be well categorized as oocyte donors are presumed fertile based on their young age and on normal ranges displayed for the parameters assessed during typical oocyte donation work-up. Participants/materials, setting, methods Donor performance was calculated according to: (I) oocyte maturation rate (MR); (ii) survival rate of cryopreserved oocytes (SR); (iii) oocyte fertilization rate (FR;2PN/Injected MII); and (iii) blastulation rate (BR;blastocyst/2PN). Donors with significantly impaired rates, considering ≥2 stimulations and/or recipients, were identified as outliers using probabilistic modelling (Binomial test, Bonferroni corrected P < 0.05). Outliers were computed for each rate on data subsets after applying this stringent filtering criteria and excluding inconsistent or missing data. Main results and the role of chance 2.6% of donors were identified as underperforming outliers when summing the rate observed for each embryological outcome using the stringent statistical modelling. The average MR was 79.8% (95%CI: 79.6-80). Taking into account the correlation of follicle size during ultrasound tracking and the number of mature oocytes collected, a total of 168/29768 (0.56%) donors with statistically lower MR (mean MR = 43% 95%CI:40.1-45.7) across ≥2 egg collection cycles were identified as outliers. The average SR was 88% (95%CI:87.9-88.2). A total of 176/18544 (0.95%) donors with ≥2 stimulations and ≥2 recipient cycles were deemed outliers, showing a statistically reduced SR (mean SR = 51% 95%CI:48.9-53.1). The average FR was 74% (95%CI: 73.8-74.2). 164/31657 (0.52%) donors were found to have statistically low FR (mean FR = 37% 95%CI:34.6-38.7) and deemed outliers when assessed over ≥2 stimulation cycles with ≥2 recipient cycles. The average BR was 53.4% (95%CI: 53.1-53.7). After considering only donors with ≥2 recipients and ≥2 stimulations, a total of 142/24716 (0.57%) donors with statistically low BR (mean BR = 14% 95%CI:12.4-15.3) were considered outliers. Limitations, reasons for caution The stringent criteria applied to our statistical modelling has likely resulted in underestimating the true level of outlier donors. This is also likely compounded by the selection bias associated with donor recruitment and the retention policies after the first stimulation cycle preventing the evaluation of recurrent patterns in some cases. Wider implications of the findings The analytical tools developed on this unprecedentedly large dataset are fundamental to define a methodological workflow for accurately identifying unexpectedly infertile individuals. This is crucial for investigating the genetic and biological mechanisms underlying infertility endophenotypes, leading to improvements in treatment and developing screening tool to predict infertility and related pathologies. Trial registration number not applicable

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 (>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 >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 < 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 < 0.0001). Likewise, LBR improved as the proportion of follicles sized 13-18mm was increased (<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-612 Euploidy rates between cycles triggered with gonadotrophin-releasing hormone agonist (GnRHa), human chorionic gonadotrophin (hCG) and dual trigger

Abstract Study question Is there any difference in euploidy rates between in vitro fertilization (IVF) cycles triggered with GnRHa, hCG or dual trigger? Summary answer There is no difference in the euploidy rate in preimplantation genetic testing for aneuploidy (PGT-A) cycles according to the trigger method used. What is known already The use of PGT-A has shown that the success of meiosis in the IVF laboratory is inversely correlated with maternal age. However, other uninvestigated factors involved in the IVF process may interfere with normal oocyte physiology. Since the final maturation obtained after ovarian stimulation depends on the use of drugs to promote the resumption of meiosis, it is worth investigating whether the triggering method could impact on oocyte and embryo euploidy. This study aims is to evaluate differences in embryo euploidy rates between PGT-A cycles triggered with GnRHa, hCG or dual trigger (GnRHa + hCG). Study design, size, duration This is a single-center retrospective study of 934 patients who underwent 1085 PGT-A cycles by Next-Generation Sequencing (NGS) from January 2017 to December 2023, using one of three possible trigger methods to induce final oocyte maturation: GnRHa, hCG, or dual trigger. The couples included in the study had normal karyotypes and no severe male factor. Participants/materials, setting, methods Data on the number of oocytes retrieved, ratio of metaphase II (MII) oocytes and fertilization rate, blastocyst development and embryo euploidy were assessed and compared between the GnRHa, hCG and dual trigger treatments. A secondary analysis was performed to evaluate data stratified by patient age. Main results and the role of chance A total of 1085 PGT-A cycles involving 934 patients (38.07 ± 3.01 years) and 2803 biopsied blastocysts were included in the analysis. Dual trigger was used in 726 (77.73%) cycles, GnRHa in 287 (26,4%) cycles and hCG in 72 (7.71%) cycles. The number of oocytes retrieved was significantly higher in the GnRHa group (GnRHa: 18.72 ± 8.59; hCG: 9.88 ± 5.64; dual trigger: 10.58 ± 5.65; p < 0.001) with similar maturation rate (GnRHa: 77.46%; hCG: 74.58%; dual trigger: 76.03%; p = 0.789), fertilization rate (GnRHa: 78.12%; hCG: 76.37%; dual trigger: 79.12%; p = 0.168), blastulation rate (GnRHa: 61.03%; hCG: 58.32%; dual trigger: 58.73%; p = 0,629), high-quality blastocyst rate (GnRHa: 27,88%; hCG: 33,67%; dual trigger: 27,88%; p = 0.543) and embryo euploidy per biopsied embryo (GnRHa: 42.48%; hCG:45.49%; dual trigger:46.98%; p = 0.112). Analysis of the data stratified by age showed similar rates of euploidy rates with the three trigger methods in women younger than 41 years (<35 years: GnRHa 66.50%; hCG 66.67%; dual trigger 56.97% p = 0.290; 35-37 years: GnRHa 49.45% hCG 51.04%; dual trigger 50.23%; p = 0.988; 38-40 years: GnRHa 40.93%; hCG 41.27%; dual trigger 39.13% p = 0.257). However, in patients ≥41 years old the euploidy rate was statistically higher in the GnRHa group (GnRH 31.51%; hCG 18.75%; dual trigger 16.89%; p = 0.032). Limitations, reasons for caution The main limitations of the study are: its retrospective design, the possibility that the trigger method was chosen based on the ovarian response and the limited number of patients in both the hCG trigger and women ≥ 41 years groups. Wider implications of the findings Our results suggest that triggering with GnRHa, hCG or dual trigger leads to comparable euploidy rates. Triggering with GnRHa should be recommended in older patients since it has been associated with a higher rate of embryonic euploidy. Trial registration number Not Applicable

P-359 Ten years’ experience using cryopreserved oocytes from In Vitro Maturation (IVM) or Controlled Ovarian Hyperstimulation (COH) cycles for fertility preservation in oncologic indications

Abstract Study question Is IVM a relevant option for fertility preservation in cancer patients, considering biological/clinical outcomes post-thawing, compared to COH? Summary answer This study shows that despite a significantly altered embryo morphology within the IVM group, the clinical outcomes remain comparable to those of COH. What is known already Fertility Preservation (FP) techniques are proposed to patients with cancer to provide the possibility of childbearing using their own gametes. Currently, oocyte vitrification after COH is the standard option. IVM serves as an alternative when COH is contraindicated, urgent cancer therapy is required, or in conjunction with ovarian cortex cryopreservation. Limited live births have been reported from frozen-thawed oocytes in IVM cycles of cancer survivors. Scarce data are available for comparing biological/clinical outcomes of frozen-thawed oocytes from IVM versus COH cycles in cancer survivors. Study design, size, duration This bicentric retrospective cohort study aimed to analyze the outcomes of all oocyte warming cycles in 73 cancer survivors having undergone oocyte vitrification for FP after COH and/or IVM. All of them had oocyte retrieval before the administration of gonadotoxic treatment and returned after being cured, with their oncologist agreement, for assisted reproduction treatments, between November 2012 and January 2024. Participants/materials, setting, methods Seventy-seven warming attempts followed by ICSI respectively from 37 COH and 40 IVM cycles were analyzed. Four patients benefited from an IVM and COH cycle. Survival, fertilization, top and good-quality embryos, defined at day-2 respectively as 4 and 3-5 adequate-sized blastomeres, without multinucleation with < 20% of cytoplasmic fragments, implantation, biochemical (hCG>100 UI/mL), clinical (intrauterine sac with fetal heartbeat) and live birth rates were compared using appropriate statistical tests. Main results and the role of chance The mean age and antral follicle count at the time of FP was similar in both groups. The indications for FP were breast cancer (n = 61), hematologic malignancies (n = 7), ovarian cancer (n = 3), other (n = 2). The number of cryopreserved oocytes tended to be higher in the COH group, when compared to the IVM group (8.5±7.3 vs 5.9±4.04; p = 0.16). The mean oocyte maturation rate after IVM was 68.6±23.1%. Oocyte survival, and fertilization rates were similar in COH and IVM groups, respectively (76.4±27.0% vs 76.1±22.0%; p = 0.76) and (67.1±34.3% vs 65.3±25.4%; p = 0.36). We reported a significantly better embryo quality at day-2 in the COH group when compared to the IVM group, with respectively top-quality embryos (44.0±34.2% vs 26.1±33.4%, p = 0,04) and good-quality embryos (62.2±38.0% vs 42.8±40.8%, p = 0.049), and also a significantly higher number of useful embryo in the COH group (2.7±2.6 vs 1.5±1.2, p = 0.03). Regarding clinical outcomes, the results were similar in COH and IVM groups, in terms of implantation rates (12.2±30.4% vs 15.5±35.6%; p = 0.86), biochemical (32.3% (10/31) vs 17.9% (6/28); p = 0.39), clinical pregnancies (25.8% (8/31) vs 17.9% (4/28); p = 0.54), live birth rates ( 25.8% (8/31) vs 14.3% (4/28); p = 0.34). Limitations, reasons for caution Statistical power to compare IVF outcomes after COH and IVM is limited by the few women who returned to use their frozen oocytes. The subjective nature of embryo morphology assessment. Wider implications of the findings This study is the largest evaluating frozen-warmed oocytes from IVM cycles in cancer patients, with 5 live births newly reported. A higher oocyte-yield may be necessary in IVM as the number of useful embryos is significantly lower. Novel approaches are being developed to improve maturation rates following IVM. Trial registration number Not applicable

P-587 Salidroside improves the reproductive capacity of aged mice via improving oocyte mitochondrial function

Abstract Study question The potential application value of salidroside as a reproductive anti-aging drug. Summary answer After old mice were intraperitoneally injected with salidroside, the reproductive function was significantly improved. This improvement is due to salidroside’s enhancement of mitochondrial function. What is known already The main cause of fecundity decline with maternal age is ovarian aging, which is characterized by decreases in follicle number and oocyte quality, However, there are currently no approved drugs for the treatment of ovarian aging. Salidroside has been regarded as an effective medicine to prevent and treat high-altitude illnesses. Emerging studies found that it also has a variety of pharmacological properties, such as anti-aging, antioxidation, anti-inflammatory and antivirus. In terms of anti-aging, salidroside supplements can extend the lifespan of fish Nothobranchius guentheri, reverse the premature senescence of human skin fibroblasts and ameliorate age-related disease. Study design, size, duration In this study, salidroside was used in two ways: First, we injected salidroside into naturally aging mice via intraperitoneal injection for 14 consecutive days and observed the fertility and ovarian reserve function of mice. Subsequently, we added salidroside to the oocyte IVM culture medium to observe changes in oocyte and mitochondrial function. Participants/materials, setting, methods Experiments were conducted in vivo and in vitro. In vivo, naturally, 10-month-old C57/B6 mice were used as treatment models. The mice were injected with 50 mg/kg salidroside every day for a total of 14 days. Then, the corresponding reproductive function. In vitro, We added 25uM salidroside to the IVM solution and conducted IVM experiments on 10-month-old GV oocytes. CGS and spindle staining observed the oocyte maturation. Main results and the role of chance We found that salidroside can increase the number of MII oocytes excreted in 10-month-old female mice, and at the same time, increase the number of pups per litter and the total number of pups. Follicle statistics showed that the addition of salidroside could increase the follicle reserve of 10-month-old female mice. Collection of GV stage oocytes. In the in vitro IVM treatment group, salidroside can delay oocyte GVBD. Improve the GVBD condition and polar body excretion of aged oocytes, At the same time, parthenogenetic activation showed that the salidroside treatment group could significantly improve the developmental ability of old parthenogenetic embryos. After 14 days of in vivo treatment, GV oocytes were collected to detect mitochondrial function. It was found that salidroside could increase the mitochondria distribution, enhance changes in mitochondrial membrane potential, and improve ROS scavenging ability. The same results were also obtained in the in vitro IVM treatment group. Limitations, reasons for caution This study found that salidroside treatment can improve ovarian aging, but the specific molecular mechanism is not clear, which is not conducive to the use of salidroside as a clinical medication. Wider implications of the findings In this study, we discovered the potential therapeutic effect of salidroside in ovarian aging and made a preliminary exploration of the therapeutic mechanism, which provides important insights into salidroside as a drug for ovarian aging. Trial registration number not applicable

O-057 Newly identified female mutations causing failed fertilization

Abstract Over the past decade, advancements in next-generation sequencing technology, alongside reduced costs, and the rising demand for infertility medical care, have resulted in the discovery of new genes and genetic variants linked to infertility conditions. Phenotypes of ICSI failure, such as oocyte maturation arrest (OMA), fertilization failure (FF) and embryo developmental arrest (EDA), can now be attributed to male or female genetic causes. This represents a transformative shift in patient treatment, allowing the identification of some cases previously classified as unexplained infertility, thereby reducing patient stress. Moreover, it facilitates personalized treatment recommendations, as well as paves the way for the exploration of novel treatment options, thus expanding research opportunities. This talk will review the genetic causes of FF following ICSI, with the main focus on the newly identified female causes, as well as give an update on current diagnostic tests and treatment options for this infertility condition. FF after ICSI still occurs in 1-3% of ICSI cycles, primarily due to oocyte activation deficiency (OAD). Defects in the male PLCζ protein, responsible of inducing calcium oscillations during oocyte activation, have long been known as the leading cause of OAD. Recent discoveries have identified genetic variants in the male genes ACTL7A, ACTL9 and IQCN, which also reduce PLCζ protein content in sperm cells and thus, contribute to FF after ICSI. Additionally, for the first time in 2018, mutations in a female gene (WEE2) crucial for oocyte activation were identified. WEE2 is an oocyte kinase that acts downstream the calcium release during fertilization. Interestingly, genetic variants in other female genes, such as PATL2, TUBB8 and CDC20 associated mainly to OMA and TLE6 and NLRP5 associated mainly to EDA, have also been described to cause failed fertilization in some patients. Determining whether the deficiency lies in sperm- or oocyte-related genes is crucial for tailoring the most effective treatment for FF after ICSI. For sperm-related factors, assisted oocyte activation (AOA), which consists in the artificial induction of calcium oscillations using calcium ionophores, has proven highly beneficial. However, most patients with oocyte-factors do not benefit from AOA (e.g. patients with WEE2 variants). In this regard, wild-type cRNA injection of the defected protein has been shown to rescue fertilization. A more generalist approach, such as maternal spindle transfer, which consists in replacing poor-quality oocyte cytoplasm with healthy cytoplasm from a donor oocyte, represents a potential treatment for these patients, as recently demonstrated in infertile females with repeated IVF failures. Nevertheless, further research into the safety of these procedures is needed before clinical application, and for now, gamete donation should be considered when facing female-related FF.

P-596 Impaired fatty acid desaturation in COV434 human granulosa cells leads to increased omega-6 phospholipid abundance

Abstract Study question How does fatty acid desaturation in COV434 granulosa cells influence their lipogenic pathway? Summary answer Suppressing fatty acid desaturation in human granulosa cells leads to a depletion of polyunsaturated phospholipids and an increase in omega-6 fatty acid-containing lipids. What is known already Maintaining the balance between saturated and unsaturated lipids in oocyte-surrounding granulosa cells is crucial to supporting oocyte maturation. We have shown the link between the de novo production of oleic acid through fatty acid desaturation and the main functional parameters of granulosa cells, such as cell proliferation and steroid production. A potential contributor to the observed pathophysiological outcomes lies in the dysregulation of cellular lipids as a consequence of insufficient intracellular oleic acid availability. This lipidomic study investigates the adaptive lipogenic response of granulosa cells to deficient fatty acid desaturation. Study design, size, duration We tested the influence of a chemical inhibitor against stearoyl-CoA desaturase 1 (SCD1), a major fatty acid desaturase enzyme, on cell membrane lipid packing, lipidome, and lipogenic-related genes in immortalized granulosa cells, COV434. We applied free oleic acid to conduct a rescue experiment. Three independent technical replicates were performed for each experimental condition, and mean values were compared among test conditions using one-way ANOVA analysis. Participants/materials, setting, methods The level of membrane fluidity was estimated using the membrane polarity-sensitive dye Laurdan. We used liquid chromatography–mass spectrometry to investigate the lipidome profiles. Data were obtained by calculating the peak areas of intact lipid species. We used quantitative PCR with TaqMan primers to assess the expression of mechanistic target of rapamycin (mTOR), diacylglycerol acyltransferase 1 (DGAT1), and fatty acid synthase (FASN), with 18S ribosomal RNA as the internal control. Main results and the role of chance Reduced oleic acid availability increased cholesterol content 1.2-fold (p = 0.007) and membrane packing, representing intended modifications in de novo desaturation. We used data comprising 459 lipid species. SCD1 inhibition caused a significant increase in dipalmitoyl phosphatidic acid 32:0 (7.4-fold increase vs. untreated controls, p < 0.001) and a substantial decrease in dioleoyl phosphatidic acid 36:2 (-38% reduction, p < 0.001). SCD1 inhibition also led to an elevation of omega-6 phospholipids (e.g., 38:4, 40:4), but conversely, a depletion of polyunsaturated lipids (e.g., 34:2, 36:2). In contrast, oleic acid supplementation resulted in an enrichment of oleic acid-containing lipids (e.g. 34:1, 36:1) but also caused a significant depletion of all polyunsaturated lipids, including omega-6 species (e.g., 20:3, 20:4). These findings indicate that the de novo generation of oleic acid intricately modulates polyunsaturated phospholipid metabolism, especially that of omega-6 phospholipids.Although the reductions in the expression levels of lipogenic-related genes due to SCDinhib treatment were not statistically significant, the addition of oleic acid significantly enhanced the suppression of FASN by 67% (p = 0.022). This suggests the presence of an interaction effect that potentiates the downregulation of the de novo fatty acid synthesis and diverts metabolic pathways away from omega-6 fatty acid production. Limitations, reasons for caution Examining lipidomic profile in isolated primary ovarian cells is crucial for a better understanding of their biological significance. Wider implications of the findings We identified that the role of de novo oleic acid generation in polyunsaturated phospholipid metabolism has significance for cellular physiology in oocyte-surrounding granulosa cells. Potential future applications include targeted metabolic interventions for reproductive disorders impacting oogenesis. Trial registration number not

P-601 Monitoring reproductive hormones during ovarian stimulation: performance and usability of a self-operated at-home urine test

Abstract Study question How effective and user-friendly is a non-invasive, patient-operated urine test (Kinder) in tracking reproductive hormone levels during ovarian stimulation (OS) treatment in an IVF cycle? Summary answer Urinary E1-3G correlates well with blood E2 levels and ovarian follicle development. Patients found it easy and stress-free to perform the urine test at home. What is known already Monitoring blood reproductive hormone levels during OS is a widely accepted practice to ensure the optimal ovarian response to gonadotropin treatment, timing of oocyte maturation triggering and mitigating hyperstimulation risk. However, conventional blood testing is invasive, necessitating patients to travel to clinics for blood sampling, adding to their overall burden. Previous studies have revealed a robust correlation between blood E2 levels, and its corresponding urinary metabolites E1-3G. Kinder is a portable device designed for quantifying urinary E1-3G, allowing patients to conduct tests in the privacy of their homes, and for many obviating the need to travel substantial distances for monitoring. Study design, size, duration This is a prospective, single-cohort, study of Caucasian patients (28-34 years), conducted at Fertility Specialists of Western Australia in Perth, Australia, where patients may travel vast distances for treatment. Twenty-five patients were enrolled from Aug 2022-Aug 2023, and performed home urine tests utilizing the Kinder device in parallel with clinic scheduled blood (ELISA) and ultrasound tests. The primary end point of the study was the correlation between urinary and blood reproductive hormone concentrations (E1-3G). Participants/materials, setting, methods Spearman and Pearson correlation coefficients (CC) and 95% confidence intervals were calculated for E1-3G and E2, and E1-3G/E2 and follicle development (total volume of ovarian follicles by ultrasound). To assess patient acceptability patient-reported outcomes (PRO) were assessed using the State Trait Anxiety Inventory (STAI) questionnaire. Further, patient-reported experiences (PRE) were evaluated through the System Usability Scale (SUS) questionnaire, along with assessing their likelihood to recommend Kinder to their friends or family undergoing IVF treatment. Main results and the role of chance Upon analysing 100 concurrent urine and blood samples from 25 patients, a robust correlation was found between E1-3G and E2 levels (Spearman CC: 0.818, 95% CI: 0.680-0.904; Pearson CC: 0.847, 95% CI: 0.712-0.939). Additionally, we observed a moderate correlation between E1-3G levels and ovarian volume (Spearman CC: 0.701, 95% CI: 0.556-0.805; Pearson CC: 0.670, 95% CI: 0.519-0.781, n = 72), resembled the correlation between E2 levels and ovarian volume (Spearman CC: 0.874, 95% CI: 0.804-0.920; Pearson CC: 0.849, 95% CI: 0.770-0.902, n = 75). PRE: 22 out of 23 patients who completed the survey confirmed that they would definitely, or probably, recommend Kinder. The mean SUS score (91.4) signified an excellent user experience. PRO: Anxiety levels were not affected by use of Kinder (STAI score below threshold of 42.38) in 18/20 patients who completed three STAI surveys (first one before and second one after the initial Kinder test; third one after the third/fourth Kinder test). Although 2/20 patients reported a STAI score of 49 in the final survey, suggesting increased anxiety, both affirmed in the PRE survey that they “will definitely recommend Kinder”, suggesting that the elevated STAI score can be attributed to the overall IVF treatment rather than the use of Kinder itself. Limitations, reasons for caution The sample size is relatively small, necessitating further multi-centre studies with a larger sample size to validate the findings. Wider implications of the findings The results suggest an acceptable interchangeability between at-home urine E1-3G and at-clinic blood E2 monitoring hormone levels during OS treatment. A digital health approach, combining tele-counselling, remote at-home hormone monitoring, and follicle tracking, could reduce patient burden and save many patients the inconvenience of travelling large distances for cycle monitoring. Trial registration number ACTRN12622000488707

P-670 The impact of fixed day-one versus day-six progestin initiation on ovarian response following progestin primed ovarian stimulation

Abstract Study question Does ovarian response differ between a fixed stimulation day (SD) 1 and SD 6 progestin start in a progestin primed ovarian stimulation (PPOS) protocol? Summary answer Fixed SD 1 and SD 6 PPOS protocols showed no significant differences in terms of ovarian response to stimulation. What is known already Ovulation prior to oocyte retrieval is a potential concern during ovarian stimulation (OS). Progestins, when compared to GnRH analogues, also effectively prevent premature ovulation with the added convenience in terms of its oral administration and lower costs. For this purpose, progestins may be started immediately with OS (SD 1) or later in the cycle, usually around SD 6, when the risk for ovulation increases. While the latter approach may be associated with a lower follicle growth suppression, evidence regarding the impact of the two protocols on ovarian response is still lacking. Study design, size, duration We conducted a single center retrospective cohort study in a private fertility clinic, including 923 patients (584 in the SD1 group and 339 in the SD6 group) who underwent 1064 OS cycles (652 in the SD1 group and 412 in the SD6 group) using a PPOS protocol between January 2016 and May 2023. Among these, 394 (37.03%) were oocyte donation cycles, 341 (32.05%) were autologous IVF/ICSI cycles and 329 (30.92%) were autologous vitrification cycles. Participants/materials, setting, methods We included women under the age of 44 who performed an OS cycle following a PPOS protocol. LH peak suppression was performed with daily desogestrel 75µg started either on SD 1 or on SD 6. The number of oocytes retrieved, number of mature (MII) oocytes, follicle-to-oocyte index (FOI) and follicular output rate (FORT) were compared between the groups. Comparisons are presented as adjusted regression coefficients (β) and 95% confidence intervals (95%CI) following multivariable linear regression. Main results and the role of chance The majority of patients in the SD1 group were donors (59.66%), while in the SD6 group most patients were doing assisted reproductive techniques (ART) with autologous oocytes (98,78%). In the SD1 group, patients were older (38.93±3.81 vs. 37.93±4.00, p < 0.001), had a higher antral follicle count (AFC) (20.79±8.66 vs. 14.12±9.96, p < 0.001), underwent OS with a lower gonadotropin dose (2036.25±766.20IU vs. 2715.20±976.40IU, p < 0.001) and triggered mostly with GnRHa (86.44% vs. 57.50%, p < 0.001). Both groups presented a similar body mass index (BMI) (22.80±2.96 vs. 21.71±3.25kg/m2, p = 0.175). Bivariate analysis revealed a higher number of oocytes retrieved (19.40±12.02 vs. 10.10±8.19, p < 0.001), number of MII oocytes (12.05±5.97 vs. 7.42±5.91, p < 0.001), FORT (81.53±20.59% vs. 73.72±23.80%, p < 0.001) and FOI (95.49±48.78% vs. 76.31±47.60%, p < 0.001) in the SD1 group. No difference was found in the cancellation rates among the two groups (1.99% for SD1 vs. 3.16% for SD6, p = 0.322). Following adjustment for age, BMI, AFC, ART treatment, type of trigger and total gonadotropin dose, no difference was found regarding the number of oocytes retrieved (β=-0.62; 95%CI -2.53 to 1.30), number of MII oocytes (β=-1.66; 95%CI -3.43 to 0.10), oocyte maturation rate (β = 2.30; 95%CI -4.60 to 9.20), FOI (β=-3.29; 95%CI -13.15 to 6.57) or FORT (β=-1.78; 95%CI -5.66 to 2.10). Limitations, reasons for caution Despite attempting to mitigate confounding effects through multivariable linear regression analysis, the retrospective nature of the study and limited sample size may still be insufficient to eliminate bias. Moreover, reproductive and perinatal outcomes were not reported. Wider implications of the findings Our study suggests that both the SD1 and SD6 PPOS protocols can be employed based on patients’ and clinicians’ preference, regardless of the type of ART treatment or patient’s ovarian reserve, without impact on ovarian response to stimulation. Trial registration number not applicable