Cause Of Infertility Research Articles

P-718 Risk of placenta previa in assisted reproduction: population study with sibling analyses from the committee of Nordic ART and safety

Abstract Study question Which treatment methods and causes of infertility contribute to the increased risk of placenta previa in assisted reproductive technology (ART)? Summary answer Risk was increased across all treatment methods and causes of infertility, but most strongly following fresh blastocyst transfer (fresh-BT) and in women with endometriosis. What is known already A higher risk of placenta previa after ART is well established. Recent studies indicate risk differences according to type of embryo transfer, with particularly high risk seen after fresh-BT. Underlying mechanisms are poorly understood, and maternal factors such as cause of infertility might contribute. Within-mother analyses, where each woman serves as her own control (i.e., sibling design), help disentangle treatment contributions from maternal confounders that are constant between pregnancies. Study design, size, duration The Committee of Nordic ART and Safety (CoNARTaS) cohort consists of linked nationwide data from health registries in four Nordic countries. Data on ART were from Medical Birth Registries (MBRs) and ART quality registries, and data on placenta previa were from MBRs and hospital discharge/specialist health care registries. We included singleton and multiple births after natural conception (NC, n = 5 614 512) and ART (n = 139 694) in Denmark (1994-2014), Finland (1990-2014), Norway (1988-2015) and Sweden (1988-2015). Participants/materials, setting, methods All women who gave their first birth during the study period, at ages 20-45 years, were included, and contributed ≤4 births at 22-44 gestational weeks. We used multilevel logistic regression to compare risk of placenta previa after ART vs NC, both at the population level and within mothers, adjusting for year, maternal age, parity and country. We categorized ART-conception according to embryo cryopreservation, culture duration, and by cause of infertility (any ART method). Main results and the role of chance Population level risk of placenta previa was higher for ART (any method) vs NC (adjusted odds ratio [aOR] 4.16, 95% confidence interval [CI] 3.96-4.37). Controlling for constant maternal factors, the association attenuated, but risk remained higher for ART vs NC (within mothers aOR 2.64, 95% CI 2.31-3.02). Compared to NC, pregnancies from fresh embryos had a higher risk increase (population level aOR 4.69, 95% CI 4.41-4.98; within mothers aOR 3.31, 95% CI 2.81-3.91) than from frozen embryos (population level aOR 2.71, 95% CI 2.35-3.13; within mothers aOR 1.59, 95% CI 1.19-2.13). Further categorization by culture duration showed highest risk increase after fresh-BT (population level aOR 11.51, 95% CI 9.75-13.57; within mothers aOR 7.80, 95% CI 4.59-13.27), and lowest risk increase after frozen cleavage stage embryo transfer (population level aOR 2.33, 95% CI 1.93-2.80; within mothers aOR 1.20, 95% CI 0.83-1.75). Similar results were found across sensitivity analyses, including restriction to singletons. Compared to NC, risk was higher across all causes of infertility, where women with endometriosis and ART-conception had the highest risk increase (aOR 9.35, 95% CI 8.50-10.29), and women with polycystic ovary syndrome who conceived by ART had the lowest risk increase (aOR 1.52, 95% CI 1.12-2.09). Limitations, reasons for caution Analyses within mothers require that women have several births, hence, results might not apply to women with a single birth. Missing data on ART method or cause of infertility made within-mother analyses by cause of infertility unfeasible. We lacked data on extent of placenta previa (low-lying placenta vs placenta previa). Wider implications of the findings Type of embryo transfer and underlying maternal factors, particularly fresh-BT and endometriosis, respectively, both contribute to the increased risk of placenta previa in ART-conceived pregnancies. Identifying the responsible mechanisms might provide opportunities for prevention. Choice of transfer type should incorporate risk of placenta previa as well as other adverse outcomes. Trial registration number NA

O-187 Real-word data on effectiveness of ICSI over conventional IVF according to infertility factors based on human fertilisation and embryology authority dataset

Abstract Study question Can the analysis of Human Fertilisation and Embryology Authority (HFEA) dataset provide real-word data on effectiveness of ICSI over conventional IVF according to infertility factors? Summary answer A statistically significant reduction in live birth rate was shown to be associated with ICSI use in cycles with female infertility factors. What is known already The adoption of ICSI has seen a considerable increase over the years, even in cases without an evident male-factor infertility. Available studies including large retrospective studies and meta-analyses evaluating the effectiveness of the two strategies tend to support the idea that in the absence of a male factor, ICSI does not offer a significant advantage over conventional IVF(cIVF). However, some uncertainties still exist regarding live birth rates and in relation to various infertility factors. Study design, size, duration Retrospective study of 275.825 first cycles treated with cIVF or ICSI between 2005-2018, included in the HFEA database. Infertility indications were simplified into three groups: 1) female only (endometriosis, tubal, ovulatory and cervical factors); 2) male (male only or with male and female factors together); 3) unexplained infertility. The primary outcome was live birth rate in the first fresh cycle. Secondary outcomes included fertilization, implantation, miscarriage rates, cycle cancellation rate and neonatal outcomes. Participants/materials, setting, methods Outcomes were evaluated through binomial logistic regression including the following predictors: female age, inseminated oocytes, number/stage of transferred embryos (condensed with principal component analysis), subtype of female infertility, year of treatment. A paired-analysis was also performed matching couples in a 1:1 ratio between ICSI and conventional IVF based on female age, indication, inseminated oocytes, year of treatment. Results were reported according to infertility cause using crude and adjusted Odds Ratios (OR) with 95%CI. Main results and the role of chance The study revealed a consistent balance in treatment distribution between conventional IVF and ICSI, with a slight increase in ICSI cycles in recent years. Based on logistic regression analysis, a significant reduction in live birth rate was demonstrated using ICSI compared to conventional IVF in cycles with female factors (adjusted OR = 0.95, 95%CI: 0.91-0.99). No significant differences emerged in unexplained factor cycles. With the use of conventional IVF, the overall odds of having a total fertilization failure increased by a factor of 1.84 (95%CI: 1.75-1.94). No significant differences in implantation rates between conventional VF and ICSI were seen after adjustment. The OR for male sex in newborns compared to female sex from single pregnancies was significantly influenced by ICSI use across the three groups of infertility causes and ranged between 0.84 and 0.87. The matched dataset confirmed a reduced occurrence of live birth per cycle in case of female factors (aOR=0.91, 95%CI: 0.86-0.96) and an overall significant lower proportion of cycles ending in cancellation for absence of viable embryos using ICSI compared to conventional IVF. Limitations, reasons for caution Some biases are intrinsic in the availability and quality of retrospective data obtained from registries and unmeasured confounders may influence the generalizability of the results. The study does not provide information on cumulative live birth rates. Wider implications of the findings ICSI introduces an additional, invasive step in assisted reproduction with a potential reduction in live birth rates for specific patients’ groups. These findings emphasize the importance of tailoring treatments to specific patient profile.The routine use of ICSI for all cases should not be considered an appropriate clinical practice. Trial registration number not applicable

O-188 Conventional in vitro fertilisation versus intracytoplasmic sperm injection in first cycle patients without severe male factor infertility (INVICSI): a randomised, controlled, open-label, multicentre trial

Abstract Study question Is the cumulative live birth rate (CLBR) after ICSI superior to conventional IVF (c-IVF) in first cycle fertility patients without severe male factor infertility? Summary answer In couples without severe male factor infertility, ICSI does not improve the CLBR compared to c-IVF after transfer of embryos from the first oocyte collection What is known already The ICSI procedure, originally developed for addressing severe male factor infertility, has seen expanded utilisation across various causes of infertility. Large retrospective studies and a recent randomised controlled trial (RCT) demonstrated comparable reproductive outcomes between ICSI and c-IVF in couples without male factor infertility. In approximately half of infertility cases, a male factor is involved, with about one-third attributed to male factor alone. Despite this, ICSI currently constitutes two-thirds of all assisted reproductive technology treatments worldwide Study design, size, duration Open-label, two-armed, multicentre RCT. A sample size of 784 women was required to detect a clinically relevant change of 10 percentage points with 80% power. Accounting for an expected 5% exclusion rate (dropouts and unexpected severely decreased quality sperm samples on the day of oocyte retrieval), 824 women were recruited from six public fertility clinics in Denmark between Nov 29, 2019, and Dec 14, 2022 Participants/materials, setting, methods Eligible participants were women aged 18-42 years and in their first treatment cycle with a partner/donor with normal or lightly to moderately decreased sperm quality. Randomisation was performed in a 1:1ratio between ICSI and c-IVF. The primary outcome was CLBR. Follow-up continued until the primary outcome was achieved or for a minimum of one year after the last participant’s inclusion.The primary outcome was assessed in an intention to treat (ITT) and a per protocol analysis Main results and the role of chance In total, 414 and 410 women were randomised to ICSI and c-IVF, respectively. Results include fresh as well as frozen-thawed embryo transfers from the first oocyte collection and are displayed as ITT. All transfers were elective single embryo transfers or single embryo transfers. The cumulative probability of achieving a live birth for couples/women undergoing ICSI was not different compared to those undergoing c-IVF (CLBR: ICSI 42.0% vs. c-IVF 46.6%, Risk ratio: 0.90, 95% CI: 0.77-1.05). The median time from inclusion to live birth did not differ between ICSI and c-IVF (309 days (IQR 268-378) vs 308 days (IQR 269-356); p = 0.12). Total fertilisation failure was seen in 4.9% of the ICSI group compared to 3.8% in the c-IVF group (Risk ratio: 1.29, 95% CI: 0.68-2.54) Limitations, reasons for caution This study was designed with 80% power to identify a 10% percentage point difference in CLBR between ICSI and c-IVF. We cannot dismiss the possibility of a smaller difference between the two methods Wider implications of the findings Our study, supported by prior research, shows that c-IVF rather than ICSI should be the first choice in initial cycles for patients without severe male factor infertility. Fertility staff should inform first cycle patients that ICSI does not increase the live birth rate for couples without severely decreased sperm quality Trial registration number NCT04128904

P-319 Chronic endometritis prevalence, associated factors and pregnancy outcome among infertile women

Abstract Study question What are the prevalence, associated factors and pregnancy outcome of chronic endometritis(CE) among infertile women? Summary answer The overal prevalence of chronic endometritis in infertile women was 24.7%. Diagnosis rate of CE was higher in primary infertility compared to other infertility groups. What is known already Chronic endometritis is defined as a chronic inflammation of uterine endometrium. The prevalence of chronic endometritis varies across different groups and diagnostic criteria. The pathophysiology of chronic endometritis remained unclear, therefore, associated factors of chronic endometritis are uncertain. Study design, size, duration We perfomed an single-center, retrospective study between May 2019 and July 2023. By doing so, we collected data on 486 infertile women. Participants/materials, setting, methods A total of 486 infertile women, who underwent hysteroscopy by single surgeon, were recruited. The diagnosis of chronic endometritis was confirmed by presence of plasma cell per section in hematoxylin-eosin stain or CD138 immunohistochemical staining. Preoperative information (including age, body mass index, smoking, alcohol consumption, clinical presentation of infertility, endometrial thickness at ovulatory phase, anti-mullerian hormone (AMH) level and infertility factors) and post-operative information (including endometrial histology and pregnancy outcome) were collected. Main results and the role of chance The prevalence of chronic endometritis in the 486 infertile women with hysteroscopy guided endometrial biopsy was 24.7%. Prevalence of chronic endometritis was 28.1%, 19%, 22.2%, 27.2% in women with primary infertility, secondary infertility, recurrent pregnancy loss (RPL) and repeated implantation failure (RIF), respectively. A multivariate analysis revealed that overweight was associated with lower risk of chronic endometritis than underweight (relative risk (RR) = 0.56, 95% confidence interval (CI): 0.32-0.98, p = 0.042). Primary infertility was associated with higher risk of chronic endometritis than non-primary infertility (RR = 1.44, 95% CI: 1.02-2.03, p = 0.039). The pregnancy rate (including spontaneous pregnancies) was comparable between women with treated chronic endometritis and without chronic endometritis; 54.7% versus 61.7% in clinical pregnancy rate and 82.8% vs 85.4% in ongoing pregnancy rate. The prevalence of chronic endometritis with coexisting endometrial lesion (endometrial polyps, submucous myoma, or both of them) was 61.7%. Limitations, reasons for caution Our retrospective study has a less powerful design compared to a prospective randomized controlled study. Wider implications of the findings In women with primary infertility, the diagnosis rate of chronic endometritis was higher compared to other infertility groups. Therefore, even in cases of primary infertility, chronic endometritis should be considered as a potential cause of infertility. Trial registration number not applicable

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.

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

P-418 What is the optimal midluteal phase circulating progesterone level during a fresh IVF cycle? The answer differs from what one expects in a natural cycle

Abstract Study question Do midluteal phase circulating progesterone (P4) levels relate to the fresh embryo transfer clinical outcome and is rescue P4 useful in such cases? Summary answer Live birth rate (LBR) was significantly lower when P4 levels were below 20ng/ml and did not seem to benefit from rescue intramuscular P4. What is known already Preceding literature on the predictive value of midluteal P4 for LBR has shown conflicting results and frequently included small sample sets and heterogeneous ovarian stimulation protocols. The findings reported ranged from the lack of an association between P4 serum levels and clinical outcome to worse success rates seen either in the groups with the highest or the lowest P4 in midluteal phase. Furthermore, while rescue P4 has been empirically proposed, it has lacked formal assessment thus far. Study design, size, duration In total, 652 patients who underwent a fresh single blastocyst transfer in an IVF cycle in our center between 2014 and 2021 were included in this retrospective cohort study. All were GnRH-antagonist cycles using hCG trigger and luteal support with micronized vaginal progesterone 200mg twice daily. Rescue intramuscular progesterone was systematically administered whenever low midluteal P4 (below 1 standard deviation of the center’s mean) levels were detected. Participants/materials, setting, methods The cycles were subdivided into three groups according to the midluteal P4 levels: <10ng/ml, 10-20ng/ml and >20ng/ml. The primary outcome assessed was LBR, with secondary outcomes including clinical pregnancy (CPR) and pregnancy loss rates. Maternal age and body mass index (BMI), year of treatment, ovarian response, endometrial thickness, cause of infertility and embryo quality were controlled for using multivariable logistic regression. Main results and the role of chance The mean age ± standard deviation of patients was 36.8±3.8 years, while mean weight and BMI were 63.2±11.5kg and 23.3±3.9kg/m2, respectively. LBR in the group with P4>20ng/ml (46.5%) was significantly higher than in the groups with low and intermediate P4 serum levels (23.1% and 28.1%, respectively, p < 0.001). The same was true for CPR (54.5%, 30.8% and 37.9%, respectively, p < 0.001). Conversely, the rate of pregnancy loss in the group with P4>20ng/ml (23.8%) was significantly lower than in the groups with low and intermediate P4 levels (42.6% and 37.5%, respectively, p = 0.018). The multivariable logistic regression confirmed that, after controlling for the confounding variables described above, P4>20ng/ml remained significantly associated with a higher LBR (OR: 2.285; 95% CI: 1.506-3.469) and a lower pregnancy loss rate (OR: 0.488; 95% CI: 0.273-0.873), irrespective of the use of rescue IM P4. Finally, a multivariable linear regression analysis of the patients baseline characteristics suggested that the only parameter predictive of midluteal P4 levels was the female patients’ weight, with an inverse relationship (adjusted regression coefficient: -0,012; 95% CI: -0,016/-0,009). Limitations, reasons for caution As the pituitary suppression, ovulation trigger and luteal support protocols used in the cycles included in the study were homogeneous (in order to maximize the internal validity of the results), this limits the extrapolibility of the results to other stimulation protocols. Furthermore, we caution that this is a retrospective study. Wider implications of the findings The usefulness of both midluteal P4 serum measurements and rescue P4 should continue to be assessed. The reasons behind the need for higher levels of P4 in a fresh cycle, when compared to natural cycles, must also be investigated. Luteal support may require personalization according to female body weight. Trial registration number Not Applicable

P-537 Linking genetic variation to infertility and embryonic genomic instability. Lessons from a database of whole genomes from targeted populations: challenges, and future directions

Abstract Study question Can novel genomic analysis methods be developed to identify genetic variants that predispose to specific types of infertility and genomic instability in embryos? Summary answer Whole genome analysis and the creation of a genomic variation database of highly targeted populations yielded several genomic links to human infertility and genomic instability. What is known already Infertility is a phenotypic manifestation that originates from highly variable causes, like repeated miscarriage (RM), repeated implantation failure (RIF) or various male and female factors. Specific genetic variations can predispose carriers to distinct types of infertility however quantifiable genetic risks are difficult to be established clinically due to the high amount of variables that exist in any relevant infertility studies. In addition, the combination of the maternal and paternal genetics further complicates the interpretation of genomics results especially when genetic instability in embryos are studied. Several studies have indicated multi[le risk variants however few have managed to establish causal relationships. Study design, size, duration The causes of infertility are extremely variable, which presents a challenge in the design and analysis of genome sequencing studies that involve large populations of participants with similar characteristics. In this study a targeted approach highly selected populations allows more detailed examination of the whole genome of the participants and the different subgroups that exist among them. The participants were recruited using specific selection criteria and samples were collected over a period of 5 years. Participants/materials, setting, methods Couples presenting with infertility and went through preimplantation genetic testing for aneuploidy (PGT- A) were invited to participate. Selection criteria were applied: i) referred for PGT-A after >3 assisted reproduction failed cycles, ii) Normal karyotypes, iii) Female age less than 37, iv) Embryonic instability in their subsequent PGT-A cycles in more than 40% of the produced embryos. After whole genome sequencing (WGS) and variant calling, a bespoke genomic SQL database was constructed for genomic analysis. Main results and the role of chance From 118 individuals that consented to participate 28 individuals with repeated implantation failure (RIF) and 8 individuals RIF/RM passed the selection criteria and their DNA was processed with WGS using a short read platform. In addition, WGS Validation was performed using genomes with known mutations. After the WGS quality control and validation. In total 50 genomes were processed and produced variant results. A novel MySQL database was successfully constructed and validated. Variant z scores were calculated for each participant and the significantly flagged variants were pulled and analysed and comparison with other bespoke and publicly available databases was performed. Ethnicity bias in novel variations detected and corrected. Several smaller cohorts were identified with similar genomic characteristics and accumulation of specific sets of polymorphisms, that were associated with certain types of infertility and preimplantation embryo abnormalities. Of particular interest were variants in synaptonemal complex genes associated with gamete failure, meiotic errors and instability in embryos. Structural variations were significant for male factor infertility. The WGS approach also revealed novel intronic and extragenic variants that would not be usually picked up by other methods like exome sequencing but can play a vital role in gene expression. Limitations, reasons for caution As with all genomic studies relating to infertility, association does not mean causation. Further functional analysis would be required to establish definitive causal pathways based on significant risk variants. In addition, although our study is highly targeted more genomic data can enhance to validation of these results. Wider implications of the findings This highly targeted study using a personalised approach to genome analysis combined with WGS can lead to protocols that determine the cumulative clinical risk for infertility, by revelling the accumulation of specific sets of polymorphisms, intronic and exonic, can be associated with certain types of infertility and preimplantation embryo abnormalities. Trial registration number not applicable

P-416 Good and bad news regarding low luteal-phase progesterone during natural cycle frozen embryo transfer: it’s rare, but rescue-therapy may not be enough to fix it

Abstract Study question Do low circulating luteal-phase progesterone levels during natural cycle frozen embryo transfer (NC-FET) affect live birth rates (LBR) and can rescue-therapy advert possible detrimental outcomes? Summary answer Low luteal-phase progesterone occurred in only approximately 3% of all FETs. However, when it occurred, LBR were lower despite the use of additional rescue-strategy. What is known already Low serum progesterone on the day of FET is known to be associated with a reduction in pregnancy rates and rescue-therapy (i.e. the increase and/or change in the route of administration of exogenous progesterone) has been shown to be useful in reducing its potential hindering effects. However, these findings are mostly limited to studies assessing artificial FET cycles. Following NC-FET, the data is not only scarce but also less clear regarding both the incidence of such low circulating levels and whether rescue-therapy may be useful in such cases or not. Study design, size, duration A total of 2292 patients (32.5% did an IVF with egg donation and 10,4% did an IVF with PGT-a) who underwent a NC-FET at blastocyst stage in a single infertility center between 2014 and 2021 were included in this retrospective cohort study. The cycles were subdivided into three groups of progesterone levels the day of FET: <10ng/ml, 10-20ng/ml and >20ng/ml. The primary outcome was LBR, with secondary outcomes including miscarriage and neonatal outcomes. Participants/materials, setting, methods Patients underwent endometrial preparation in either a true, modified or natural proliferative phase (NPP) NC-FET. Luteal-phase support was routinely provided using micronized vaginal progesterone. Rescue intramuscular progesterone was systematically administered whenever low midluteal progesterone (below 1 standard deviation of the center’s mean) levels were detected. Maternal age and body mass index (BMI), year of treatment, ovarian response, endometrial thickness, cause of infertility and embryo quality were controlled by means of a multivariable logistic regression. Main results and the role of chance The mean age (± standard deviation) of patients was 38.3±4.5 years, while mean weight and BMI were 62.6±10.7 kg and 23.3±3.7kg/m2, respectively. Only 72 (3.1%) cycles had FET day circulating progesterone below 10 ng/mL, while 1084 (47.3%) and 1136 (49.6%) had 10-20 ng/mL and >20 ng/mL, respectively. The unadjusted LBRs in the subgroup with progesterone <10ng/ml, 10-20ng/ml and >20ng/ml were, respectively, 43.5%, 52.7% and 49.6%, differences that were not statistically significant in this non-adjusted analysis (p = 0.151). However, following confounder adjustment using multivariable logistic regression, progesterone <10ng/ml was associated with a lower LBR (adjusted odds-ratio 0.568; 95% confidence interval 0.330-0.977), a finding that occurred despite the aforementioned use of rescue progesterone therapy in this subgroup. The miscarriage rate, in the <10ng/ml subgroup was higher (26.1%), but without statistically significance, comparing to other subgroups (19% and 20.5% respectively). Limitations, reasons for caution This study is limited by its retrospective design. Moreover, as different NC-FET protocols were included, further research should be performed to assess whether this effects differs according to each protocol. Also the number of embryos transfered varied also affecting the final conclusion. Wider implications of the findings This study raises the hypothesis that low midluteal progesterone may be rare in NC-FETs. However, to our knowledge, it is also the first to posit that rescue-therapy may be insufficient to restore adequate endometrial function. Further research should assess eventual pathophysiological differences between artificial and NCs to justify such findings. Trial registration number not applicable

P-456 Sexual attitudes in men undergoing Infertility treatment:Turkish sample

Abstract Study question 1. What are the sexual attitudes in men undergoing Infertility treatment ? Summary answer When the infertility reason arises from their spouse, men tend to display a more self-centred sexual attitude. What is known already Men experiencing infertility often hesitate to seeking information or ask questions about sexuality due to prevailing societal norms.Health professionals predominantly focus on addressing women’s issues, leaving the male partner feeling like an outsider who observes the treatment process from a distance. Study design, size, duration This research was conducted in cross-sectional type.,September and December 2017. 141 participant. Participants/materials, setting, methods 141 men who applied to an infertility clinic in Istanbul on Tuesdays and Thursdays between September 2017 and December 2017. The participants’ inclusion criteria were as follows: being men between the ages of 18-49, literate, accepting to participate, and having no diagnosed psychiatric illness.. All men meeting the sampling criteria were invited to participate, and there were no refusals. This setting accepts couples who have been married for at least one year and infertility problems. Main results and the role of chance The mean score of Hendrick Sexual Attitude Scale (HSAS) was 69.78 ± 9.46. Among its subscales, Birth Control had the highest mean score (11.95 ± 2.81), while Instrumentality had the lowest mean score (10.43 ± 4.34). Men whose spouse was over 30, whose marriage age was over 27, and the cause of infertility was unexplained had higher HSAS mean scores. Additionally, men with male-factor infertility scored higher in HSAS than female-factor infertility. Healthcare professionals involved in infertility treatment must prioritise addressing the sexuality of both partners. Male partners may struggle in this aspect, leading to potential misunderstandings or incomplete understanding of sexual information. By addressing and dispelling erroneous cognitive schemas, false beliefs, and self-centred attitudes, healthcare professionals can play a significant role in supporting both partners in their sexual well-being throughout the infertility treatment process. Providing sexual counselling for couples, both jointly and individually, can have a positive impact. However, it is essential to recognise that male partners may be reluctant to engage in such counselling, resulting in suppressed problems and thoughts. Healthcare providers must actively involve male partners and encourage them to share their feelings and concerns professionally and openly. Limitations, reasons for caution The participants included from a single outpatient clinic and little sample size which may limit the generalizability of the findings. Due to the topic’s taboo in Turkish society, some men might not feel openly expressing their thoughts and feelings while answering the questions, potentially affecting the accuracy of the responses. Wider implications of the findings The findings of this research highlight the significance of further investigations into men facing infertility issues from various cultural backgrounds. Qualitative and quantitative research can offer valuable insights into the complexities of sexual attitudes in diverse cultural settings. Collobaration between infertility clinics and liaison psychiatry may be advantageous. Trial registration number not applicable

O-278 The vaginal and endometrial microbiome: do they tell the same story?

Abstract Study question Is the composition of the endometrial microbiome comparable to that of the vagina and can vaginal sampling provide sufficient information to characterize the uterine microbiome? Summary answer The compositions of the endometrial and vaginal microbiome are largely comparable and therefore, in most cases, vaginal sampling is sufficient to characterize the uterine microbiome. What is known already A dysbiotic endometrial microbiome (i.e., a shift from a predominance of beneficial bacteria to less favourable species) has been reported in association with adverse pregnancy outcomes in assisted reproductive treatment (ART). If dysbiosis is detected, antibiotics or probiotics can be administered to restore an optimal microbiome. However, characterization of the endometrial microbiome is challenging, involving invasive sampling, and technical difficulties due to the low microbial mass in the endometrium. In contrast, vaginal sampling is considered minimally invasive and microbial analysis is technically less complex. It is important to clarify whether the microbiomes of the endometrium and the vagina are comparable. Study design, size, duration A prospective multi-centre study including 60 ART patients was conducted from June 2022 to August 2023. During the luteal phase (on average day-19), paired vaginal swabs and endometrial biopsies were collected sequentially and stored in a preservation medium for further analysis. Patients and physicians were also asked to complete a questionnaire to identify any lifestyle or medical factors that may have differentially affected the microbial composition of the vagina and endometrium. Participants/materials, setting, methods A carefully validated qPCR methodology was used to accurately assess the presence and relative abundance of the four major lactobacillus species associated with eubiosis (crispatus, gasseri, iners, and jensenii) and the 15 most common bacterial species implicated in dysbiosis. Additionally, the relative abundance of microbial and human DNA was examined. Of note, endometrial analysis required additional tissue lysis. Furthermore, due to the low microbial DNA content in endometrial samples, preamplification was necessary prior to qPCR. Main results and the role of chance The proportion of microbial versus human DNA was approximately 90 times higher in vaginal samples compared to endometrial samples (p < 0.0001). However, the microbial compositions of both the endometrium and the vagina showed remarkable similarities. Lactobacillus species were predominant at both sites, accounting for an average of 86% and 89% of the bacterial population in the vagina and endometrium, respectively (p = 0.6). Of the dysbiotic species, Gardnerella vaginalis was the most common, accounting for 8% (vagina) and 7% (endometrium) of the total bacterial population (p = 1). There was no difference in the average number of distinct microbial species between the two niches (1.8 vs. 2.1; p = 0.3). Direct comparison of paired samples highlighted the high similarity of microbial compositions between both sites and showed strong correlations of species abundances in individual patients (L.crispatus: r = 0.9, L.iners: r = 0.9, L.gasseri: r = 1, L.jensenii: r = 0.9, G.vaginalis: r = 0.7; p < 0.0001/all species). However, the microbial composition differed in four patients (6.6%), with three having a dysbiotic vaginal profile (≥50% dysbiotic species) but a eubiotic endometrial profile (≥50% lactobacillus species) and one showing the reverse pattern. The medical conditions of two patients, including chronic endometritis and use of antibiotics and probiotics in the preceding cycle, may account for the observed differences. Limitations, reasons for caution The species analysed were carefully selected to ensure a comprehensive analysis. Nevertheless, the potential presence of unevaluated species could impact the results. While the included patients displayed diversity in their reproductive histories, it is important to acknowledge that the observed results may still be influenced by underlying causes of infertility. Wider implications of the findings The close similarity between the microbiomes at the two sites investigated suggests that minimally invasive vaginal sampling may be sufficient to characterise the endometrial microbiome. The ease of vaginal sampling and processing is expected to improve patient recruitment in microbiome research and facilitate easier application of clinical microbiome tests. Trial registration number not applicable

O-262 Karyotyping of single sperm from non-obstructive azoospermia patients and obstructive azoospermia patients using a combination of micromanipulation and next-generation sequencing

Abstract Study question Is there a difference in the frequency of aberrant karyotype in sperm when the cause of infertility is non-obstructive azoospermia (NOA) versus obstructive azoospermia (OA)? Summary answer Aberrant karyotype was found in 7 of 46 sperm with NOA, none of 26 sperm with OA and none of 28 sperm with control. What is known already It is known that aberrant karyotype occurs more frequently in sperm from infertile men than sperm from general population, and that the severity of infertility is proportional to the frequency of sperm chromosomal abnormality. In fact, miscarriage rates are high in cases where TESE-ICSI is performed for azoospermia, and embryonic chromosomal aneuploidy derived from sperm is thought to be one of the causes of miscarriage. Azoospermia is classified into OA and NOA. However, it is unclear whether there is a difference in the frequency of sperm chromosomal abnormality between NOA and OA. Study design, size, duration Sperm were picked up individually by micromanipulation for the OA and NOA groups who underwent TESE in clinical practice. For comparison, ejaculated sperm from males who underwent IVF or ICSI for female infertility were picked up. As a quality control, ejaculated sperm from balanced reciprocal translocation (RcT) carriers were also picked up. Each sperm was karyotyped by next-generation sequencing (NGS) to compare the number of normal haploid sperm and aberrant sperm. Participants/materials, setting, methods Under the ethical review of Yokohama City University and informed consent with patients, we collected human sperm which were discarded after clinical use. Sperm samples were picked up individually by micromanipulation. Following whole-genome amplification (WGA), karyotyping was performed by NGS. For each sperm, if even one of all chromosomes had abnormality, that sperm was counted as aberrant sperm, and if all chromosomes were haploid, it was counted as haploid sperm. Main results and the role of chance We analyzed 10 sperm per patient. Karyotyping analysis was performed on sperm from 2 patients in the RcT group,4 patients in the control group, 4 patients in the OA group, and 5 patients in the NOA group. WGA was successful in 90% (18/20) of RcT carriers group, 95% (38/40) of the control group, 72.5% (29/40) of the OA group, and 92% (46/50) of the NOA group. Acquisition rate of karyotyping was 90% (18/20) of RcT carriers group, 70% (28/40) of the Control group, 65% (26/40) of the OA group, and 95% (46/50) of the NOA group. The results of karyotype analysis showed 28 haploid sperm and no aberrant sperm in the control group, 26 haploid sperm and no aberrant sperm in the OA group, and 39 haploid sperm and 7 aberrant sperm in the NOA group. Karyotyping of sperm from RcT carriers group showed sperm with unbalanced chromosomes derived from translocations of the carriers. The frequency of aberrant karyotype was significantly higher in NOA than control (P = 0.0297). It was also higher in NOA than OA(P = 0.0363). Limitations, reasons for caution In our research, micromanipulation was performed manually to isolate sperm, and the number of sperm that could be analyzed was small. Sperm with good morphology are selected using micromanipulation and analyzed by NGS, so the results do not reflect the results of all sperm actually collected by TESE. Wider implications of the findings In this study, sperm with good morphology were selected by micromanipulation and analyzed, so it is thought that the karyotype of sperm actually reflects the karyotype used in clinical practice. These results suggest that PGT-A is particularly effective in preventing miscarriages among patients whose azoospermia was caused by NOA. Trial registration number not applicable

The Prevalence of Gonadal Changes in Patients with Congenital Adrenal Hyperplasia

Abstract Background Adrenal rest tumours can appear in early childhood in patients with congenital adrenal hyperplasia(CAH). The common cause of infertility in males with CAH is testicular adrenal rest tumours (TARTs). Ovarian adrenal rest tumour (OART) and polycystic ovaries (PCO) can impair the ovarian function in female patients with CAH. Objective Detect the prevalence of gonadal changes by imaging among patients with CAH andassess the patients' radiological findings in relation to their hormonal profile. Patients and Methods This observational, cross sectional study was conducted on 50 patients with CAH. Testicular ultrasonography was done to male patients and magnetic resonanceimaging (MRI) of the pelvis was done to female patients. Data on prescribed glucocorticoid dose and serum levels of 17- hydroxyprogesterone (17-OHP), androstenedione (Andro) and ACTH were obtained from medical records within endocrinology clinic, Children's Hospital, Ain Shams University. Results TARTs were detected in 10/20 (50%) of CAH patients. There was significant relationbetween presence of TARTs and each of weight standard deviation score (SDS), body mass index (BMI), BMI SDS and current bone age (p = 0.028, 0.046, 0.017 and 0.023; respectively). There was no significant relation between presence of TARTs and the laboratory parameters or the treatment received (p > 0.05). There was significant correlation between Tanner testicular volume and mean testicular volume by ultrasound (p < 0.001). Only one female patient had bilateral polycystic ovaries (prevalence 3.3%) and none had ovarian adrenal rest tumours. Conclusion The prevalence of TARTs in male patients in our study is high (50%), highlighting the importance of TARTs screening in children with CAH. We would suggest that routine ovarian imaging in CAH females is not indicated. However, when ovarian dysfunction is present, ovarian imaging is advised.

P-532 Preimplantation genetic testing versus morphology as selection criteria for single embryo transfer in women aged 35-42: results of a pilot randomized controlled trial

Abstract Study question To assess the feasibility of running a large randomised controlled trial (RCT) evaluating the benefit of preimplantation genetic testing for aneuploidy (PGT-A) for embryo selection. Summary answer Running a PGT-A RCT is feasible. Considerations include participant recruitment, seven-day biopsy-embryologist availability and logistical complexities. What is known already Critics question the effectiveness of PGT-A leading to concerns about false positives and negatives, unnecessary embryo discarding and clinical effectiveness. Past studies have been criticised for only performing biopsy on top quality embryos, their criteria for randomization and the age of the population being assessed. Given these uncertainties there is a need for a rigorous RCT evaluating the role of PGT-A using current methodologies and biopsy techniques in women most affected by aneuploidy. Our pilot study is the first study where all embryos generated will undergo biopsy and ranked in terms in implantation potential prior to transfer. Study design, size, duration In this prospective, concealed allocation two-arm parallel RCT, our goal was to randomise 100 women with ≥3 good quality embryos on day 3 post egg collection into two groups: embryos screened using next-generation sequencing (NGS)-based PGT-A or selection-based on morphology alone. PGT-A patients underwent a trophectoderm biopsy on day 5/6/7 following egg collection. Biopsied embryos were frozen and subsequently transferred. Euploid and embryos described as being low mosaic (<30% abnormal cells) were prioritised for transfer. Participants/materials, setting, methods Women aged between 35–42 years undergoing IVF±ICSI were included, with those undergoing PGT for inherited genetic disorders, gamete donation cycles, untreated hydrosalpinges or untreated uterine abnormalities excluded. Primary objective during the pilot phase was to assess the ability to recruit, randomise, adherence to the study protocol and plan for a full study. Secondary outcomes were clinical pregnancy rate per embryo transferred, clinical pregnancy rate per couple randomised, miscarriage rate and time to pregnancy. Main results and the role of chance Out of 247 eligible women,100 were randomised, and 94 received the assigned treatment. The recruitment rate was 70.18%(173/247, 95%CI 61.65%-78.70%). An average of 6 participants were randomised each month. All randomised participants completed the follow-up. Our main recruitment challenges included 19% of eligible patients choosing to have PGT-A privately and 6% withdrawing their consent choosing to have a fresh transfer. Lack of biopsy-embryologist also meant patients whose potential biopsy would have been on a weekend had to be excluded in the first 4 months of our recruitment process. Baseline characteristics including age, BMI and cause of infertility were comparable in both arms and a total of 56 euploid, 53 aneuploid and 3 low mosaic embryos were identified. There was no statistically difference in CPR (23/50 vs 21/50, RR 1.09 95%CI:0.83-1.15, p-value>0.23) and miscarriage rate (3/50 vs 2/50, RR 1.5 95%CI:0.84-1.75, p-value: 0.15) per single embryo transfer or per woman randomised (23/46 vs 21/48, RR 1.14 95%CI 0.78-1.27, p-value:0.24 and 3/46 vs 2/48, RR 0.72 95%CI 0.58-1.17 p-value: 0.17) in either arm of the study. We cannot yet confirm the clinical benefit of PGT-A owing to the insufficient sample size in this pilot study. No low mosaic embryos were transferred. Limitations, reasons for caution The study was conducted in a single centre. If future definitive trials are conducted in multiple centres, the criteria for recruitment, randomisation, intervention, and follow-up still need to be unified. Many women aged above 40 failed to reach randomization due to challenges in producing three good-quality embryos. Wider implications of the findings The pilot study found that the eligibility rate is adequate however researchers should consider reviewing the conditions for randomisation in main study such as reducing the number of good embryos required to two. In addition, stratified randomization should be used in order to better balance female age within each group. Trial registration number NCT05009745

P-310 Impact of adenomyosis on the live birth rate during management by in vitro fertilization : a French study

Abstract Study question Evaluate the impact of adenomyosis on the likelihood of live birth after a fresh embryo transfer. Summary answer Adenomyosis reduces the live-birth rate. The location of adenomyosis and the type of protocol appears to have no impact on the live birth rates. What is known already The prevalence of adenomyosis varies between 7 and 27%, and affects 25% of infertile women. Its impact on fertility remains debated. According to some studies, it leads to a lower pregnancy rate, a doubling of the spontaneous miscarriage rate and a lower live birth rate as compared to non-adenomyosis women. However according to some authors adenomyosis does not reduce the live birth rate. Similarly, the impact of the location of adenomyosis remains debated. On the impact of the stimulation protocol, several studies have shown that the use of GnRH agonist improves the live birth rate in patients with adenomyosis. Study design, size, duration This is a retrospective, descriptive and observational study, managed at the fertility department of Dijon University Hospital between January 2015 and March 2020. Systematically, the women infertility cause was assessed. We compared the group of patients with adenomyosis (i.e. symptomatic adenomyosis completed with a 3D ultrasound within a maximum of 1 year prior to management) with controls (i.e. patients treated for another cause of infertility). Ultrasound was performed by the same two experienced operators. Participants/materials, setting, methods We included 340 patients aged 18-41 years. Data concerning live births and type of stimulation protocol were collected from the patient’s electronic medical and therapeutic records. MUSA classification was used to determine whether the adenomyosis was localized or diffuse. The primary endpoint of this study was the live-birth rate (LBR) after fresh embryo transfer. The implantation and miscarriage rates were also compared. Main results and the role of chance We included 92 patients in adenomyosis group, and 248 patients in control group. Baseline characteristics of patients including women age, BMI and smoking habits were comparable in both groups. Moreover, no difference was found on the mean number of mature oocytes and embryos between the two groups. LBR after fresh embryo transfer was significantly lower in the adenomyosis group than in the control (34.8 % versus 41.5%, respectively, p = 0,02). There was no significant difference in implantation rate (35.7% versus 37,4%, p = 0.76). Early miscarriage rate (<12 weeks of amenorrhea) was higher in the control group than the adenomyosis group (15.3 versus 7.5, p = 0.012). Concerning late miscarriage (>12 weeks of amenorrhea), we observed 3 medical termination of pregnancy (all for fetal malformation) and 1 miscarriage (10%) in the adenomyosis group and 1 miscarriage (0.81%) in the control group (p = 0.02). Subgroup analyses showed no decrease in LBR according to adenomyosis location (32.7% versus 37.2% in the diffuse and localized groups, respectively, p = 0.46). Limitations, reasons for caution Even though our cohort is a good reflection of the all-French population of Burgundy since all patients are treated at the fertility center of Dijon. Despite its retrospective nature and the small number of included adenomyosis-patients, the ultrasound scans were performed by two experienced operators that reduced inter-observer variability. Wider implications of the findings It would be useful to carry out a prospective study including more patients to better assess the impact of location on implantation. It would also be interesting to evaluate neonatal and obstetrical complications, especially the late miscarriage issue requiring further investigation. Trial registration number non-clinical trials

P-421 Enhancing the success of frozen embryo transfer by human chorionic gonadotropin injection on the day of progesterone supplementation onset - a machine learning study

Abstract Study question Does subcutaneous injection of human chorionic gonadotropin (hCG) at the onset of progesterone supplementation affect clinical pregnancy rate in frozen embryo transfer cycles? Summary answer Clinical pregnancy rates are higher when hCG injection is administered at the onset of 300 mg/day progesterone in patients undergoing frozen embryo transfer. What is known already HCG and progesterone play crucial roles in embryo transfer and implantation during in vitro fertilization. Exisitng studies have demonstrated that pre-administration of hCG at the onset of progesterone supplementation for frozen embryo transfer increases clinical pregnancy rates in patients with endometriosis. However, the synergistic effects of hCG and progesterone co-supplementation in a broader range of patients remain unexplored and require further investigation. A multifactorial analysis of hormone replacement therapy, covering various patient-specific aspects, is necessary to understand the implications of this approach. Study design, size, duration This retrospective cohort study analyzed data from 2,251 single frozen embryo transfers performed between Jan 2019-Aug 2023 at the INVICTA Fertility Centre, Poland. The dataset was selected by the practitioner and included age, AMH, BMI, embryo morphology grade, total number of transfers, medical and embryological procedures, recurrent implantation failure, preimplantation genetic testing, endometrial thickness before transfer (≥ 7 mm), and the menstrual cycle day on which progesterone was started. Participants/materials, setting, methods Patients (21-47 years) receiving 300 or 600 mg/day progesterone for five days were divided into the control and hCG (6,500 IU hCG injection on progesterone onset) groups. A machine learning model was trained using a gradient boosting technique (100 decision trees, four leaves, maximum depth of two nodes, learning rate of 0.05) to identify factors affecting the clinical pregnancy rate. Statistical analysis was performed to compare clinical pregnancy rates between the groups. Main results and the role of chance Our machine-learning model revealed that hCG injection (512 processes vs. 1739 processes without it) at the onset of progesterone administration is an important feature for the clinical pregnancy rate. The performance accuracy of the model was approximately 70%. Of the 1,294 protocols where patients received 300 mg/day progesterone, 311 included hCG injection while 983 did not. The clinical pregnancy rate was significantly higher in the hCG group than that in the control group (54% vs. 46%, P < 0.05), with 167 clinical pregnancies observed in patients receiving hCG injections against 452 pregnancies without it. In contrast, among the 957 protocols where 600 mg/day progesterone was administered, the previously observed effect was not significant (P > 0.05). Comparing 201 processes with hCG injection to 756 processes without it, the incidence of clinical pregnancies was 46.8% and 47.2% (with 94 and 357 confirmed pregnancies), respectively. Other factors such as the morphology grade of the embryo used for transfer, patient’s age, AMH, BMI, total number of transfers performed on the patient, menstrual cycle day on which progesterone was started, occurrence of recurrent implantation failure, and the use of preimplantation genetic testing were not significantly different between the groups. Limitations, reasons for caution This study focused on frozen embryo transfers and validation across other protocols using fresh embryo transfers, and different doses or routes of hCG and progesterone administration are needed. The impact of hCG administration on patients with various causes of infertility should also be explored. Wider implications of the findings Pre-administration of hCG injection along with a daily dose of 300 mg/day progesterone enhanced clinical pregnancy rates for frozen embryo transfer. This holds the potential for the optimization of hormon supplementation protocols to increase overall success rates in assisted reproductive technologies. Trial registration number not applicable

P-769 Congenital heart defects in children born after assisted reproductive technology: A large cohort study from the Committee of Nordic Assisted Reproductive Technology and Safety (CoNARTaS)

Abstract Study question Are children conceived after assisted reproductive technology (ART) more likely to be born with congenital heart defects (CHDs) than those born after spontaneous conception (SC)? Summary answer Major CHDs and severe CHDs are associated with ART, with a higher risk in both ART-conceived singletons and multiples compared to singletons from SC. What is known already Children born after ART have higher risk of birth defects compared to children born after SC. Among these defects, CHDs hold the highest prevalence, accounting for about 50% of all major birth defects and affecting approximately 1-2% of children in the general population. Several cohort studies and systematic reviews, among these a recent review including 41 studies and in total 25,856 ART children, shows increased risk of CHDs in children born after ART. However, conflicting findings have been reported for specific CHDs. Study design, size, duration This Nordic registry-based cohort study included 7,747,637 liveborn children, with 171,735 conceived after ART. All liveborn children (singletons and multiples) in Denmark (1994–2014), Finland (1990–2014), Norway (1984–2015), and Sweden (1987–2015) were included. National data from ART registries, medical birth registries, patient registries, cause of death registries, and population registries were cross-linked. Participants/materials, setting, methods The International Classification of Diseases (ICD) versions 8, 9, 10 were used for selection of CHDs. Major and severe CHDs were defined according to European Concerted Action on Congenital Anomalies and Twins (EUROCAT). Outcomes were major CHDs, severe CHDs, six hierarchical CHD lesion groups, and ten selected major CHDs. CHD diagnoses were considered prenatally or within the first year of life in Denmark, Finland, Sweden, and prenatally or at birth in Norway. Main results and the role of chance Major CHDs occurred among 1.84% (n = 3159) children born after ART and among 1.15% (n = 86,824) children born after SC, with adjusted odds ratio (AOR) 1.36; 95% CI 1.31–1.41. Risk was highest in multiples, regardless of conception method. Severe CHDs were detected in 0.35% (n = 594) children born after ART and in 0.26% (n = 19,375) children born after SC; AOR 1.30; 95% CI 1.20–1.42. When analysing the risk of CHD for the specific groups of CHDs by the hierarchical classification, children born after ART had higher risk of CHDs than children born after SC for five of the six lesion groups: conotruncal defects, non-conotruncal defects, ventricular septal defect, atrial septal defects, and other CHDs. ART was further associated with an elevated risk in four of ten selected major CHDs. Major CHDs occurred among 1.62% (n = 2059) singletons born after ART and among 1.11% (n = 18,539) singletons born after SC; AOR 1.19; 1.14–1.24. The prevalence of severe CHDs was 0.31% (n = 399) among singletons born after ART and 0.25% (n = 18,539) among singletons born after SC; AOR 1.20; 95% CI 1.09–1.33. In singletons born after ART, no difference was seen between ICSI and IVF or between frozen and fresh embryo transfer for major CHDs or severe CHDs. Limitations, reasons for caution A main limitation in this study is the lack of information on CHDs in miscarriages, pregnancy terminations, and stillbirths. Another limitation is that information on specific techniques used in assisted reproduction was not available from Finland. Lastly, we did not have information on causes of infertility. Wider implications of the findings CHDs, although rare, imply severe risks. Our study reveals an association between ART and major CHDs. While most CHD-affected children survive to adulthood, high morbidity and mortality rates persist in childhood and adulthood. The potential benefit of fetal echocardiography screening in ART pregnancies, beyond routine obstetric ultrasound, remains uncertain. Trial registration number ISRCTN 11780826

O-205 Dydrogesterone versus micronized vaginal progesterone for luteal phase support in hormone replacement therapy frozen embryo transfer cycles (REMODEL): an exploratory randomized controlled trial

Abstract Study question Is dydrogesterone (DYD) comparable to micronized vaginal progesterone (MVP) for luteal phase support (LPS) in hormone replacement therapy frozen embryo transfer (HRT-FET) cycles? Summary answer Ongoing pregnancy rates (OPR) at 12 weeks’ gestation were comparable between the study group using DYD and the control group using MVP. What is known already Thanks to vitrification, the number of frozen embryo transfer cycles has significantly increased, prompting for a thorough optimization. Few studies have prospectively compared different progesterone regimens in artificial frozen embryo transfer cycles. Currently, MVP is most commonly used for LPS in this setting, but side effects such as vaginal discharge cannot be neglected. Dydrogesterone, a selective progesterone receptor agonist with a high oral bioavailability, could be considered due to its more patient-friendly administration. Two randomized controlled trials confirmed the non-inferiority of dydrogesterone to MVP for LPS in fresh cycles, but robust data on its use in HRT-FET cycles remain limited. Study design, size, duration An exploratory randomized controlled trial was conducted at a university hospital from October 2021 to September 2023. Subjects were randomly allocated 1:1 to the study group using DYD (10mg three times daily) for LPS or the control group using MVP (2x200mg twice daily), all performing FET in a HRT cycle. The primary outcome was ongoing pregnancy rate at 12 weeks (OPR). Secondary objectives included biochemical pregnancy loss, early pregnancy loss (EPL) and live birth rate. Participants/materials, setting, methods Patients under 41 years of age with a normal BMI undergoing a single blastocyst transfer in a HRT-FET cycle without endometrial abnormalities were eligible for inclusion. Patients who required more than 14 days of estradiol valerate priming (2mg three times daily) to achieve an endometrial thickness of at least 7 mm were not included. Of the 170 patients screened, 19 did not meet the randomization criteria and 3 withdrew after randomization. Main results and the role of chance Demographic characteristics such as age, BMI, cause of infertility and regular cycle were comparable between the study and control groups, as were the frozen transfer cycle characteristics. With three drop-outs after randomization, both a per-protocol (PP) and an intention-to-treat (ITT) analysis were performed for the primary outcome. According to the PP analysis, the OPR was 31.5% in the study group and 45.3% in the control group (p = 0.08, difference in proportions (%) -14, 95% CI: -39-11). The ITT analysis showed similar results (OPR 31.1% versus 44.2% in the study and control groups, respectively, p = 0.10). Multivariate regression adjusting for age, BMI, endometrial thickness and parity showed no significant association between the type of LPS administered and OPR (OR 1.92, 95% CI 0.95-3.86, p = 0.07). Positive hCG rates were comparable between both groups (58.9% versus 61.3% in the study and control groups, p = 0.76). Differences in biochemical pregnancy loss (14.0% versus 2.2% in the study and control groups, respectively, p = 0.05) and EPL (32.6% versus 23.9% in the study and control groups, respectively, p = 0.37) did not reach statistical significance. The live birth rate did not differ significantly between the two groups (26.8% versus 41.9%, p = 0.06), but the delivery outcome of 3 patients is missing to date. Limitations, reasons for caution Despite the randomized nature of the study, the exploratory design warrants cautious interpretation of the results due to the primary outcome’s insufficient statistical power. The dosages of the LPS medication used are based on common clinical practice, but due to the absence of dose-finding studies, this may impact the results. Wider implications of the findings The results, although not statistically significant, may raise clinical implications and call for larger studies. A forthcoming analysis will assess progesterone levels throughout the cycle in these study patients, examining their impact on pregnancy outcomes. Given differences in pharmacological profiles, various dosages may also be explored. Trial registration number NCT04758871

O-127 Blastocyst expansion speed assay: a putative artificial intelligence-powered tool for embryo selection. Retrospective study involving 2184 blastocysts and 786 PGT-A cycles

Abstract Study question Is blastocyst expansion-speed, examined through Artificial-Intelligence (AI) between time of blastulation (tB) and time of expanding blastocyst (tEB), associated with embryo blastulation and reproductive competence? Summary answer Blastocyst expansion-speed-assay (ESA) was significantly associated with euploidy and live-birth rates, being discordant with clinical embryologists’ ranking in 50% of embryonic cohorts. What is known already Blastocyst expansion is one of the earliest morphogenetic events in mammalian development. It is essential for the establishment of the blastocyst layout and requires trophectoderm integrity. Several studies suggested that expansion is a valuable feature for ranking and prioritizing blastocysts for transfer based on their developmental competence. Time-lapse technology (TLT) implementation in IVF allows a deeper understanding of blastocyst expansion dynamics. In this study, we combined TLT and AI to develop a blastocyst-ESA and investigate its association with embryo blastulation and reproductive competence. Study design, size, duration Retrospective study including 2184 blastocysts cultured in EmbryoScope incubators during 786 PGT-A cycles across 2013-2020. Videos were analyzed through an AI-powered tool (CHLOETM, Fairtility). The expansion-speed was calculated as [(Δ embryo proper area at tEB – embryo proper area at tB) / (Δ tEB - tB)]. ESA was tested for its association with embryo quality, euploidy and live-birth rate (LBR) in 548 vitrified-warmed single euploid transfers. A simulation of ESA putative clinical effectiveness was conducted. Participants/materials, setting, methods ICSI, trophectoderm biopsy of fully-expanded blastocysts without day3 zona-drilling, and qPCR/NGS to assess full-chromosome uniform aneuploidies were performed. tB and tEB, expressed as hours-post-insemination (hpi), embryo proper area (in µm2) at both these stages, and blastocyst quality (EQ-Score from 0 to 1) were all automatically recorded through CHLOE. Possible confounders (e.g., maternal age, male factor, and cause of infertility) were considered. Regression analyses were conducted to adjust the data. Main results and the role of chance The average ESA was 705±458 µm2/hour. Higher ESA was associated with higher EQ-Score. Euploid blastocysts showed higher ESA than aneuploid (761±465 µm2/hour versus 667±449 µm2/hour; p < 0.01). ESA was also associated with LBR per euploid blastocyst transfer (LB: 873±438 µm2/hour versus 736±467 µm2/hour; p < 0.01). Of note, maternal age showed no association with ESA. Multivariate regressions outlined a + 5.1%-increase in the chance of euploidy and a + 6.3%-increase in chance of LB, every +100 µm2/hour-increase in ESA. ESA and embryologists were discordant in grading top-quality embryos in each cohort in 50% of the cases. In 59% of the 352 cohorts where both euploid and aneuploid blastocysts were obtained, ESA would have ranked the former embryos as top-quality. In the 216 cycles with ≥2 euploid blastocysts obtained and ≥1 transferred, ESA would have prioritized (i) a competent embryo in 46% of the cases, (ii) an incompetent embryo in 20%, but (iii) in 33% its value could not be assessed (i.e., the top embryo according to ESA has not been transferred yet). When compared to the embryologists, ESA would have been (i) equally-effective in 49% of the cases, (ii) more effective in 12-24%, and (iii) less effective in 5%-26%. Limitations, reasons for caution Retrospective single-center study. Both continuous and sequential media were used, although they were not associated with the outcomes under investigation. To assess the clinical value of ESA, a prospective study among first transfers is warranted. Wider implications of the findings ESA is an automated, unbiased, and easily-applicable measurement that certainly deserves further appraisal. If validated in prospective studies, AI-based selection algorithms could include this assessment to increase their predictive power. Trial registration number None

O-207 Comparison of the pregnancy outcomes of transferring frozen embryos versus fresh embryos among advanced maternal age women: a nationwide analysis of 232,942 cycles

Abstract Study question Are there differences in pregnancy outcomes when comparing frozen embryo transfer versus fresh embryo transfer among aged women? Summary answer Frozen embryo transfer yields lower live birth rate for women aged 35-39, but higher rate for women ≥40 compared to fresh embryo transfer. What is known already Advanced maternal age was defined as over 35 years old, while recent literature lifted the threshold to 40. An increasing number of women are postponing childbirth, but reproductive issues become more common after the age of 35, with a significant decline in fertility, particularly after 40, even with IVF. Advanced age affects pregnancy rates, prompting some clinicians to prefer fresh embryo transfer to achieve pregnancy quickly. However, it may be less effective with potential negative effects of ovarian stimulation on endometrial receptivity. Frozen embryo transfer is seen as a better strategy, but data specific to advanced maternal age is lacking. Study design, size, duration This cohort study analyzed the Human Fertilization and Embryology Authority anonymized data from 2011 to 2018 in the United Kingdom. This comprised of a total of 232,942 cycles with advanced maternal age, in which 65,066 patients undergoing frozen embryo transfer cycles, and 167,876 patients undergoing fresh embryo transfer cycles. Participants/materials, setting, methods Data on women with advanced maternal age undergoing IVF/ICSI cycles were analyzed to compare live birth rate and miscarriage rate. The cycles with patients’ age <35, donor oocyte / embryo, PGT, or without embryo to transfer were excluded. Log-binominal regression analysis was performed adjusting for patient age, cause of infertility, number of embryos transferred, year of treatment, and IVF or ICSI cycle. Main results and the role of chance We analyzed data from 232,942 cycles with patients age ≥35, and found that FET cycles exhibited a higher live birth rate than that of fresh embryo transfer cycles (25.5% vs. 24.9%, RR, 1.03; 95% CI, 1.01–1.123). Miscarriage rate (4.6% vs. 3.3%, RR, 1.41; 95% CI, 1.35–1.48) was also different. However, the adjusted RR (aRR) of live birth rate was 0.91; 95% CI, 0.88–0.93, after adjusting for potential confounders. For those patients aged 35-39, live birth rate (28.4% vs. 29.7%, aRR, 0.86; 95% CI, 0.83–0.88) following FET cycles was lower than that of fresh embryo transfer cycles. While FET cycles showed a higher rate of miscarriage (4.6% vs. 3.2%, aRR, 1.83; 95% CI, 1.70–1.98). When patients age≥40, FET cycles showed a higher rate of live birth (18.2% vs. 14.0%, aRR, 1.24; 95% CI, 1.16–1.32) and miscarriage rate (4.7% vs. 3.4%, aRR, 1.72; 95% CI, 1.52–1.94). Besides the live birth rate was sharply decreased than patients aged 35-39 both in FET and fresh embryo transfer cycles. Limitations, reasons for caution The conclusion of the present study might be limited by the anonymous nature of the dataset. Further randomized trials may be required to provide direct evidence for the best embryo transfer strategy for the advanced age women. Wider implications of the findings The study shows that FET exhibited a higher live birth rate in women aged ≥ 40, but lower for those aged 35-39 than fresh embryo transfer. Additionally, FET demonstrated a higher miscarriage rate. Therefore, it is necessary to tailor the embryo transfer strategy for advanced maternal age women. Trial registration number not applicable