Progestin-primed Ovarian Stimulation Research Articles

A multicycle approach through DuoStim with a progestin-primed ovarian stimulation (PPOS) protocol: a valuable option in poor prognosis patients undergoing PGT-A.

This study is to evaluate the effectiveness of a PPOS protocol in poor prognosis patients undergoing IVF with DuoStim and PGT-A versus the conventional protocol with GnRH antagonist. Retrospective cohort study encompassing 444 couples obtained matching one PPOS-DuoStim with two antagonist-DuoStim cycles at a private IVF center between 2020 and 2023 (averagematernal age: 40years, averagecumulus-oocyte complexes collected after the first stimulation: 5). The study was powered to exclude a two-sided different euploid blastocyst rate per MII oocytes (EBR per MII) in the two groups (alpha = 0.05, power = 0.9, effect size = 0.3). All cycles involved ICSI, blastocyst stage PGT-A, and single vitrified-warmed euploid transfers. We compared all embryological and clinical outcomes within each group (first vs. second stimulations), and among the two study arms (first stimulation vs. first stimulation; second stimulations vs. second stimulation; overall). The overall EBR per MII was the primary study outcome. The cumulative-live-birth-rate per concluded cycles (CLBR) was the main secondary outcome. In the second stimulations, we obtained a greater number of COCs and MIIs in both antagonist- and PPOS-DuoStim groups. No difference was observed for all embryological and clinical outcomes when comparing the two stimulations within each group. All embryological and clinical outcomes were comparable also between the two groups, including the EBR per MII. To date, 285 and 121 antagonist- and PPOS-DuoStim cycles were concluded. The CLBR was comparable between the groups: 26% vs. 29%. PPOS-DuoStim holds potential for being an efficient, patient-friendly, and possibly cost-effective approach that does not compromise treatment efficacy. Future investigations must explore PPOS effect on follicular recruitment, neonatal, and long-term outcomes.

Progestin-primed ovarian stimulation outcomes in in-vitro fertilization (IVF) – A systematic review of the literature

Background: Progestin-primed ovarian stimulation (PPOS) stimulates ovaries to block the premature surge of luteinizing hormone (LH) by using micronized progesterone or a progestin during the follicular phase instead of the conventional gonadotropin-releasing hormone (GnRH) analogues or GnRH antagonists downregulating LH to obtain multi-follicle engagement. Current work aims to assess the influence of progestogen treatment on ovarian stimulation and the ability to control LH surge, its efficacy and suitability in retrieving oocytes, without affecting the embryo quality and its benefit among infertile women long-term outcomes on children compared to standard stimulation protocols. Materials and Methods: The literature review used the randomized control trials published in the Pubmed database from January 2015 to April 2021. To generate the citation list, the following keywords were used: ‘progestin-primed ovarian stimulation’, ‘PPOS’, ‘micronized progesterone’, ‘medroxyprogesterone’, and/or ‘dydrogesterone’. The selected articles analyzed the cohort, intervention, and scheme of the progestin-primed ovarian stimulation protocol in controlled ovarian stimulation (COS) for in-vitro fertilization (IVF)/intra cytoplasmic sperm injection (ICSI) used in Assisted Reproductive Technologies (ART). Results: Overall we concluded that PPOS for IVF/ICSI in ART results in a higher number of obtained embryos, lower incidence of OHSS, equal duration of stimulation, number of retrieved oocytes, and number of MII oocytes. It is also suggested that long-term safety in children shows no significant difference between the study and control groups. Conclusions: Despite the outcomes of progestin stimulation cycles among all cohorts, we concluded that poor ovarian responders, patients with PCOS, women of advanced age and oocyte donors benefit the most from using PPOS.

The PPOS protocol mitigates the detrimental effects of high BMI on embryo and clinical pregnancy outcomes

BackgroundThe impact of high body mass index (BMI) on embryo and pregnancy outcomes in women using the PPOS (progestin-primed ovarian stimulation) protocol during their first frozen embryo transfer (FET) cycles is not clear. This study is to investigate the impact of BMI on oocyte, embryo, and pregnancy outcomes in patients who underwent the PPOS protocol.MethodsThis retrospective study included the first FET cycle of 22,392 patients following the PPOS protocol. The impact of BMI on oocyte and pregnancy outcomes was assessed across different BMI groups, using direct acyclic graph to determine covariates, followed by the application of multiple linear and logistic regressions to further validate this influence.ResultsThe high BMI groups exhibited a higher number of oocytes; however, no significant differences were observed in good-quality embryos, clinical pregnancy rate, and implantation rate. Nevertheless, the high BMI groups demonstrated a significantly elevated miscarriage rate (9.9% vs. 12.2% vs. 15.7% vs. 18.3%, P < 0.001), particularly in late miscarriages, resulting in lower live birth rates (LBR, 41.1% vs. 40.2% vs. 37.3% vs. 36.2%, P = 0.001). These findings were further confirmed through multiple liner and logistic regression analyses. Additionally, several maternal factors showed significant associations with adjusted odds ratios for early miscarriage. However, women with a BMI ≥ 24 who underwent hormone replacement cycle or hMG late stimulation protocol for endometrial preparation experienced an increased risk of late miscarriage.ConclusionsBy utilizing the PPOS protocol, women with a high BMI exhibit comparable outcomes in terms of embryo and clinical pregnancies. However, an elevated BMI is associated with an increased risk of miscarriage, leading to a lower LBR. Adopting appropriate endometrial preparation protocols such as natural cycles and letrozole stimulation cycles may potentially offer benefits in reducing miscarriages.

Comparison of highly purified human menopausal gonadotropin and recombinant follicle stimulating hormone use in patients undergoing in vitro fertilization with progestin-primed ovarian stimulation protocol: a single center retrospective analysis.

Recently, progesterone has been used to prevent LH surge instead of GnRH analogues during ART treatments, which is known as progesterone-primed ovarian stimulation (PPOS) protocol. During ART treatment, highly purified human menopausal gonadotropin (HP-hMG) and recombinant follicle stimulating hormone (rFSH) are two of the agents used for stimulation of antral follicles. The aim of this study is to compare the efficacy and success of HP-hMG and rFSH agents in the ovarian stimulation step of the PPOS protocol, which has not been previously reported in the literature. This retrospective study was conducted at a university hospital with patients who underwent IVF treatment using PPOS protocols in between January 2019 and July 2021. For ovarian stimulation, rFSH was used in group I and HP-hMG was used in group II. Mature oocyte ratio was the primary outcome, and live birth rate was the secondary outcome. Mann-Whitney and Chi-square tests were used for statistical analysis. All p values below 0.05 were considered significant. Total numbers of follicles, oocytes, MII, and 2PN numbers obtained were similar between the two groups. The fertilization rates were 66.7% in the rFSH group and 64.3% in the HP-hMG group (p > 0.05). The pregnancy rates were 53.5% and 46.7% in the rFSH and HP-hMG groups, respectively. There was no statistically significant difference between pregnancy, abortus, and live birth rates. In this study, it is demonstrated that stimulation of oocytes with either rFSH or hMG in the PPOS protocol, which has been added to IVF treatment protocols in recent years, had no statistical difference regarding mature oocyte numbers and live birth rates between the two groups. These results are consistent with the previous literature which compared rFSH and hMG in GnRH agonist and antagonist protocols.

Exposure of antral follicles to medroxyprogesterone acetate during stimulation does not cause molecular perturbations in gonadotropin-responsiveness and steroidogenic function of granulosa cells in progestin-primed cycles.

Does medroxyprogesterone acetate (MPA) exposure in progestin-primed ovarian stimulation (PPOS) cycles cause molecular perturbations in the steroidogenic function and gonadotropin responsiveness of the granulosa cells? PPOS cycles are identical to traditional GnRH antagonist cycles not only for clinical IVF characteristics but also for gonadotropin receptor expression, response to gonadotropins, and steroidogenic function at the molecular level. PPOS is increasingly used as an alternative to GnRH antagonists due to the inhibitory effect of progesterone on LH release by reducing GnRH pulsatility at the hypothalamic level. Although a growing body of evidence from clinical studies did not indicate significant differences between PPOS and antagonist protocols for IVF cycle characteristics and obstetrical outcomes, it is still unknown whether exposure of the antral follicle cohort to progesterone or its synthetic derivatives during ovarian stimulation causes any subtle molecular aberrations in terms of steroidogenesis and gonadotropin responsiveness. To address this issue, detailed comparative molecular analyses were conducted in the luteinized mural granulosa cells (GCs) obtained from normal responding IVF patients undergoing PPOS and antagonist cycles. A clinical translational research study was conducted with IVF patients. This study included 55 normal responding IVF patients who underwent ovarian stimulation with either PPOS using MPA (5 mg twice daily) or GnRH antagonist cetrorelix acetate. Recombinant forms of FSH and hCG were used for ovarian stimulation and ovulation triggering, respectively. Luteinized mural GCs obtained during the oocyte retrieval procedure were used for the experiments. Cell culture, quantitative real-time PCR, immunoblotting, confocal time-lapse live cell imaging, and hormone assays were used. Demographic and IVF cycle characteristics of the patients undergoing ovarian stimulation with PPOS and GnRH antagonist were similar, including ovarian response, mature oocyte yield, and fertilization rates. Molecular analyses revealed that the expression of the enzymes involved in sex-steroid synthesis (StAR, SCC, 3β-HSD, 17β-HSD, aromatase) and the uptake/storage/utilization of cholesterol (LDL receptor, Hormone-sensitive lipase, hydroxy-methyl glutaryl Co-enzyme-A reductase, and Sterol O-acyltransferase1) in the GCs of the PPOS cycles were comparable to those of the antagonist cycles. The expression of the receptors for gonadotropins, estrogen, and progesterone hormones was also similar. Basal and hCG-induced increases in 3β-HSD expression and progesterone production and basal and FSH-induced increases in aromatase expression and E2 output of the GCs from PPOS patients did not exhibit any meaningful differences when compared with GCs from antagonist cycles. Furthermore, basal and hCG-induced up-regulation in the LDL receptor expression and cholesterol uptake did not differ between the groups. Confocal imaging also revealed similar patterns of expression for the steroidogenic enzymes and their co-localization with mitochondria. Lastly, the expression of the other important genes regulating cumulus expansion, ovulation, and luteal function [Relaxin, ADAMTS-1, and epidermal growth factor (EGF)-like growth factor amphiregulin] in the GCs of the PPOS and antagonist cycles were similar. N/A. Caution should be exercised when interpreting our data which was derived from normally responding patients whose ovulation was triggered with hCG. It is unclear whether the molecular parameters assessed vary according to infertility etiologies, magnitude of ovarian response, mode of trigger, and any other underlying ovarian pathologies or systemic diseases. MPA was the progestin used for PPOS and whether these findings can be generalized to other progestins is unknown. This study provides reassuring molecular evidence that exposure of antral follicle cohorts to MPA during the follicular growth phase does not have any detrimental effects on steroidogenic, ovulatory, and luteal functions when compared with GnRH antagonist cycles. This study was funded by the School of Medicine, the Graduate School of Health Sciences of Koc University and Koç University Research Center for Translational Medicine (KUTTAM), and equally funded by the Republic of Turkey Ministry of Development Research Infrastructure Support Program. All authors declare no conflict of interest. N/A.

Progestin-primed ovarian stimulation

The use of progestins for the prevention of premature ovulation during ovarian stimulation is called progestin-primed ovarian stimulation (PPOS). Response to ovarian stimulation with PPOS and gonadotropin-releasing hormone (GnRH) analogs seem to be similar with the clinically insignificant differences being explained by endocrine characteristics as expected. PPOS has the advantage of oral administration and lower medication cost than GnRH analogs, but the mandatory cancellation of an otherwise possible fresh embryo transfer can render PPOS less cost-effective if a fresh transfer would have been possible. Oocytes collected in PPOS cycles have similar developmental potential, including blastocyst euploidy rates. Frozen embryo transfer outcomes of PPOS and GnRH analog cycles seem similar both in terms of ongoing pregnancy/live birth rates and obstetric and perinatal outcomes. While some studies reported lower cumulative live birth rates with PPOS, they suffer from methodological issues, including arbitrary definitions of cumulative live birth rates. PPOS has been used in all patient types with consistent results and seems a patient-friendly and cost-effective choice when a fresh embryo transfer is not intended.

Comparison of fixed and flexible progestin-primed ovarian stimulation in women classified in patient-oriented strategies encompassing individualized oocyte number (POSEIDON) group 4.

This study aimed to compare the fixed and flexible protocols for progestin-primed ovarian stimulation (PPOS) in poor ovarian responders. This retrospective study included 95 poor ovarian responders classified using the Patient-Oriented Strategies Encompassing Individualized Oocyte Number group 4 criteria. Treatment involved assisted reproductive medicine using fixed and flexible PPOS protocols at Shiga University of Medical Science between July 2019 and August 2023. PPOS cycles were assigned to the fixed and flexible groups at the discretion of attending physicians. The results of assisted reproductive medicine were compared between groups. The fixed and flexible groups included 68 and 27 patients, respectively. The flexible group obtained more retrieved oocytes and two pro-nuclei than the fixed group, without an early luteinizing hormone surge. Multiple linear regression analysis demonstrated that differences in protocols and anti-müllerian hormone (AMH) levels were related to the number of retrieved oocytes. The differences in protocols were more strongly correlated with the number of oocytes than with the AMH levels. Among poor ovarian responders, the flexible PPOS protocol provided more retrieved oocytes than the fixed PPOS protocol, possibly because the total dosage of progestins was lower in the flexible group and progestins were not administered at the time when ovarian stimulation was initiated.

The construction of machine learning-based predictive models for high-quality embryo formation in poor ovarian response patients with progestin-primed ovarian stimulation

ObjectiveTo explore the optimal models for predicting the formation of high-quality embryos in Poor Ovarian Response (POR) Patients with Progestin-Primed Ovarian Stimulation (PPOS) using machine learning algorithms.MethodsA retrospective analysis was conducted on the clinical data of 4,216 POR cycles who underwent in vitro fertilization (IVF) / intracytoplasmic sperm injection (ICSI) at Sichuan Jinxin Xinan Women and Children’s Hospital from January 2015 to December 2021. Based on the presence of high-quality cleavage embryos 72 h post-fertilization, the samples were divided into the high-quality cleavage embryo group (N = 1950) and the non-high-quality cleavage embryo group (N = 2266). Additionally, based on whether high-quality blastocysts were observed following full blastocyst culture, the samples were categorized into the high-quality blastocyst group (N = 124) and the non-high-quality blastocyst group (N = 1800). The factors influencing the formation of high-quality embryos were analyzed using logistic regression. The predictive models based on machine learning methods were constructed and evaluated accordingly.ResultsDifferential analysis revealed that there are statistically significant differences in 14 factors between high-quality and non-high-quality cleavage embryos. Logistic regression analysis identified 14 factors as influential in forming high-quality cleavage embryos. In models excluding three variables (retrieved oocytes, MII oocytes, and 2PN fertilized oocytes), the XGBoost model performed slightly better (AUC = 0.672, 95% CI = 0.636–0.708). Conversely, in models including these three variables, the Random Forest model exhibited the best performance (AUC = 0.788, 95% CI = 0.759–0.818). In the analysis of high-quality blastocysts, significant differences were found in 17 factors. Logistic regression analysis indicated that 13 factors influence the formation of high-quality blastocysts. Including these variables in the predictive model, the XGBoost model showed the highest performance (AUC = 0.813, 95% CI = 0.741–0.884).ConclusionWe developed a predictive model for the formation of high-quality embryos using machine learning methods for patients with POR undergoing treatment with the PPOS protocol. This model can help infertility patients better understand the likelihood of forming high-quality embryos following treatment and help clinicians better understand and predict treatment outcomes, thus facilitating more targeted and effective interventions.

P-583 The ploidy status in blastocysts generated from progestin primed ovarian stimulation and GnRH antagonist protocols: A comparison of 14.000 trophectoderm biopsies

Abstract Study question Is there any difference in the euploidy rate in a large cohort of blastocysts when produced after a progestin-primed or GnRH antagonist protocol? Summary answer Euploidy rates in trophectoderm biopsies when tested with next-generation sequencing (NGS) were similar after progestin-primed or GnRH antagonist protocol. What is known already Preimplantation genetic testing (PGT) might be employed in patients with advanced female age to improve efficiency of embryo transfer. Given the fact that there is no fresh embryo transfer in that policy, progestin primed ovarian stimulation (PPOS) protocol might be preferred over GnRH analogs due to its lower cost and advantage of oral administration instead of s.c injections. However, due to small sample sizes within the limited number of studies, there is lack of consensus whether ploidy status might be affected when an embryo is generated after a PPOS or GnRH analogs protocol. Study design, size, duration A retrospective cohort study was designed among patients that has undergone in-vitro fertilization (IVF) treatment between January-2018 and June-2023 in Bahceci Health Group. For the aim of PGT, only patients treated with PPOS or GnRH antagonists were included. PPOS protocol referred to utilization of either medroxyprogesterone acetate (10 mg/day) or dydrogesterone (20-30 mg/day) to avoid premature ovulation during ovarian stimulation. In GnRH antagonist protocol, flexible or fixed approach was preferred for pituitary suppression. Participants/materials, setting, methods During the study period, 11.616 and 2.480 trophectoderm biopsies had been performed from blastocysts (D5/6) generated after GnRH antagonist or PPOS protocol, respectively. Of them, 9.390 and 1.801 of them were analyzed with NGS. A total of 303 (3.2%) and 17 (0.9%) biopsies were excluded due to failure or non-informative results after testing. For the final analysis, 9.087 and 1.784 biopsies were included in the antagonist and PPOS arms for the current study. Main results and the role of chance The mean age of women treated with GnRH antagonist and PPOS was comparable (36.5±5.3 vs. 36.7±5.4 years, p = 0.17). The respective numbers of euploid embryos were 3.912 and 1.784. Per biopsied embryos, the rate of euploidy was 33.7% and 34.8% (p = 0.30). The rate of euploidy per metaphase II oocyte and 2-PN were 10.6% and 13.5% in the GnRH antagonist arm and they were 11.3% and 14.4% in the PPOS arm (p = 0.08 and p = 0.07) without any statistical significance. When only patients included in whom all available blastocysts were biopsied, the linear regression model revealed only female age (RR: -0.32 CI%95: -0.38 to – 0.26, p &amp;lt; 0.001) as the independent factor for the prediction of ploidy rate (euploid/euploid + aneuploid embryos) when body mass index, duration of infertility, AMH, number of oocytes, number of metaphase-II oocytes, and the type of ovarian stimulation protocol were entered into the model. This model represented female age as the sole independent factor (RR: -0.14 CI%95: -0.18 to – 0.11, p &amp;lt; 0.001) when euploidy rate per 2PN was tested with the same variables. Limitations, reasons for caution The inherent risks cannot be excluded due to the retrospective nature of the current study. Wider implications of the findings The current study includes the largest number of trophectoderm biopsies generated from PPOS and GnRH antagonist protocol, giving the opportunity to compare them with each other. Due to lack of any superiority of one protocol regarding ploidy status, financial cost and easiness might favor PPOS when PGT is planned. Trial registration number None

Comparison of aneuploidy for patients of different ages treated with progestin-primed ovarian stimulation or GnRH antagonist protocols

Does euploidy status differ among patients of different ages treated with progestin-primed ovarian stimulation (PPOS) or gonadotrophin releasing hormone antagonist (GnRH-a) protocols? Patients undergoing PGT-A (n = 418; 440 cycles) were enrolled and grouped according to female age (<35 years and ≥35 years). Protocols were as follows: PPOS: <35 years (n = 131; 137 cycles); ≥35 years (n = 72; 80 cycles); GnRH-a: <35 years (n = 149; 152 cycles); ≥35 years (n = 66; 71 cycles). For cycles treated with PPOS in the older group, rates of euploid blastocyst per metaphase Ⅱ oocyte (15.48% versus 10.47%) and per biopsied blastocyst (54.94% versus 40.88%) were significantly higher than those treated with GnRH-a (P < 0.05). The mosaic rate per biopsied blastocyst was significantly lower for cycles treated with PPOS than cycles treated with GnRH-a (8.64% versus 23.36%) (P < 0.001). In the younger group, no significant difference was found between treatments (P > 0.05). In older and younger groups, the drug to inhibit LH surge was cheaper for cycles treated with PPOS compared with GnRH-a (P < 0.001). Generalized estimation equations based on binomial distribution female age and euploidy rate was significantly negatively correlated for all participants (β -0.109, 95% CI -0.183 to -0.035, P = 0.004), and between GnRH-a protocol (reference: PPOS) and the euploidy rate in the older group (β -0.126, 95% CI -0.248 to -0.004, P = 0.042). Multiple logistic regression indicated that ovarian stimulation protocol was not associated with ongoing pregnancy rate (OR 0.652, 95% CI 0.358 to 1.177; P = 0.14). PPOS is suitable for patients undergoing PGT-A, particularly older patients for the higher euploid blastocyst rate attained by PPOS protocol.

O-299 Exposure of antral follicles to progestins during stimulation does not cause molecular perturbations in gonadotropin-responsiveness and steroidogenic function of granulosa cells in progestin-primed IVF cycles

Abstract Study question Does progestin exposure cause any molecular perturbations in the steroidogenic features and gonadotropin responsiveness of the granulosa cells in progestin-primed ovarian stimulation (PPOS) cycles? Summary answer No. PPOS cycles are identical to antagonist cycles for gonadotropin receptor expression, response to gonadotropins, steroidogenic function at molecular level in normal responding IVF patients. What is known already PPOS is commonly used in IVF cycles as an alternative to antagonist cycles. Although accumulating evidence from clinical studies did not indicate any particular differences between these two types of stimulation protocol for IVF cycle characteristics, it is still unknown if exposure of antral follicle cohorts to synthetic progesterone derivatives during ovarian stimulation causes any subtle molecular aberrations in PPOS cycles in terms of steroidogenesis and gonadotropin responsiveness. To address this issue, detailed molecular analyses were conducted in the luteinized mural granulosa cells (GCs) obtained from the normal responding patients undergoing PPOS vs. antagonist IVF cycles. Study design, size, duration A translational research study in IVF patients. Participants/materials, setting, methods 55 normal responding IVF patients underwent ovarian stimulation either with PPOS using medroxy progesterone acetate (5mg twice daily) or, with GnRH antagonist cetrorelix acetate were included in the study. Recombinant forms of FSH and hCG were used for ovarian stimulation and ovulation trigger, respectively. Luteinized mural granulosa cells obtained during oocyte retrieval procedure were used for the experiments. Cell culture, quantitative real-time PCR, immunoblotting, confocal time-lapse live cell imaging and hormone assays were used. Main results and the role of chance Demographic and IVF characteristics of the patients undergoing ovarian stimulation with PPOS vs. GnRH antagonist were similar including ovarian-response, mature oocyte yield and fertilization rates. Molecular analyses revealed that the expression of the enzymes involved in sex-steroid synthesis (StAR, aromatase, 3B-HSD, 17B-HSD) and uptake/storage/utilization of cholesterol (LDL receptor, Hormone-sensitive lipase, hydroxy-methyl glutaryl Co-enzyme-A reductase and Sterol O-acyltransferase1) in the GCs of the PPOS cycles were comparable to the antagonist IVF cycles. Both cycles were also similar for the expression of FSH and LH receptors at transcriptional and translational level. Basal and hCG-induced increases in 3B-HSD expression and P4 production, and basal and FSH-induced increases in aromatase expression and E2 output of the GCs of the PPOS patients did not show any meaningful differences from the antagonist cycles. Similarly, basal and hCG-induced up-regulation in the LDL receptor expression and cholesterol uptake rate did not differ between the groups. Confocal imaging also revealed similar patterns of expression for the steroidogenic enzymes and their co-localization with mitochondria. Lastly, the expression of the other genes regulating cumulus expansion, ovulation and luteal function (Relaxin, ADAMTS-1 and EGF-like growth factor amphiregulin (AREG)) in the GCs of the PPOS cycles were comparable to the antagonist cycles. Limitations, reasons for caution Caution should be exercised when interpreting our data, which was produced in normal responders. It is unclear if the molecular parameters assessed here vary according to infertility etiologies, ovarian response type, mode of trigger and any other underlying ovarian pathology or systemic diseases that are concomitantly present. Wider implications of the findings This study provides reassuring molecular evidence that exposure of antral cohorts to progestins follicular growth phase does not appear to have any detrimental effect on their steroidogenic, ovulatory and luteal functions, suggesting that PPOS IVF cycles are not different from traditional antagonist cycles. Trial registration number not applicable

P-702 New era in donor programs. Is it time to leave behind the antagonist for a progestin-primed ovarian stimulation protocol? Retrospective cohort analysis of 711 cycles

Abstract Study question Are GnRH-antagonist and progestin-primed ovarian (PPOS) stimulation protocols comparable in terms of effectiveness and efficiency in an egg donor program? Summary answer The PPOS protocol would have similar efficacy to the antagonist protocol, despite a slightly lower rate of useful blastocyst, without impact on recipient’s clinical results. What is known already There are numerous studies based on the comparison of oral progestin (P) vs. subcutaneous GnRH-antagonist (A) as pituitary suppressors during ovarian stimulation with gonadotropins, showing similar results in terms of ovarian response and reproductive outcomes in IVF cycles. Limited data are available on the comparison of both protocols in egg donor programs to evaluate their effectiveness and efficiency. Study design, size, duration Retrospective and observational cohort study with 711 oocyte donor cycles included over 18 months (July 2022-Dec 2023). As pituitary suppressors during ovarian stimulation, Ganirelix was used in 394 cycles and Medroxyprogesterone in 317. We obtained 626 reception cycles (369 from A group and 257 from P group). 499 egg-recipients underwent an embryo transfer (309 form A group and 190 from P group). Live birth rates were calculated only over the 192 informative embryo transfer cycles. Participants/materials, setting, methods Variables such as duration of the ovarian stimulation, number of mature oocytes (MII), maturation rate, fertilization rate, useful blastocysts (uBL) rate and their quality (&amp;gt;3BB/≤3BB), clinical pregnancy and live birth rate, have been evaluated. An economic analysis has been conducted for both protocols. Statistical analysis was performed using T-Student and Chi-Square tests. Main results and the role of chance There were no significant differences between groups A and P in terms of: average stimulation days (11.44±1.45 vs. 11.39±1.38, p = 0.62), average number of MII (15.69±7.46 vs. 15.12±7.12, p = 0.30), maturation rate (78.97% vs. 80.01%, p = 0.13), and fertilization rate (68.6% vs. 70.1%, p = 0.15). However, a statistically significant difference was observed in the rate of viable blastocyst formation (uBL/2PN) between groups A and P (70.4% vs. 66.8%, p &amp;lt; 0.05), although there were no differences in embryo qualities obtained (&amp;gt;3BB: 89.4% vs. 90.6%, ≤3BB: 10.6% vs. 9.1%, p = 0.083). Regarding obstetric outcomes, no differences have been found in live birth rates between the two groups (52,4% vs 64,5%, p = 0,11). The cost of the antagonist protocol was significantly higher being 8.48% more expensive than the oral progestin protocol (p &amp;lt; 0.05). Limitations, reasons for caution A regulated randomization has not been used to assign donors to both treatments. The population size, although enough to provide significant differences, could be wider. The number of cycles performed with P are smaller compared to A. Most clinical pregnancy are still ongoing so these data are lacking Wider implications of the findings Besides being more donor-friendly, the progestin-primed ovarian stimulation offers a significant economic advantage. Both protocols have proven similar efficacy. Clinical data are necessary to evaluate the impact of the lower BLu rate on the reproductive outcomes. Trial registration number Not applicable

P-577 A randomized trial to compare the live birth rate following the progestin-primed ovarian stimulation versus the antagonist protocol in women with anticipated high ovarian responses

Abstract Study question Is there difference in the live birth rate following the progestin-primed ovarian stimulation (PPOS) versus the antagonist protocol in women with anticipated high ovarian responses? Summary answer The live birth rates of the first frozen embryo transfer following PPOS and the antagonist protocol were comparable in women with anticipated high ovarian responses. What is known already Progestin when given orally inhibits the pituitary LH surge during ovarian stimulation when taken orally i.e. progestin-primed ovarian stimulation. Two randomized trials showed similar number of oocytes for PPOS and the antagonist protocol in oocyte donation cycles. However, there is still no randomized trial to compare the live birth rate between PPOS and the antagonist protocol. Study design, size, duration This is a randomized controlled trial of 784 infertile women conducted from June 2020 and October 2021. Participants/materials, setting, methods Infertile women aged &amp;lt;43 years undergoing the first IVF cycle in a tertiary fertility center and having antral follicle count &amp;gt;15 randomly assigned in a 1:1 ratio into two groups: PPOS group and the antagonist group. Medroxyprogesterone 10 mg daily was given from the start of ovarian stimulation until the day of ovulation trigger in the PPOS group. The primary outcome was the live birth rate of the first frozen embryo transfer. Main results and the role of chance 784 women were randomly assigned into two groups: PPOS group (n = 392) and antagonist group (n = 392). Embryo transfer was either cancelled or postponed in 62 (62/392, 15.8%) women in the PPOS group and 65 (65/392, 16.6%) in the antagonist group because of no transferable embryos or no frozen embryo transfer within 6 months following randomization. The two groups were similar in demographic characteristics and number of oocytes obtained/fertilized, the number of cleaving embryos, number of good quality embryos at day 3, number of blastocysts developed and number of embryo/blastocyst frozen. There was no statistically significant difference in the live birth rate of the first frozen embryo transfer cycle between the progestin-primed ovarian stimulation and antagonist groups based on both intention to treat [37.5.0% (147/392) versus 32.7% (128/392), RR 1.148 (95% CI = 0.949–1.390), P = 0.16] and per protocol analysis [44.5% (147/330) versus 39.1.% (128/327), RR 1.138 (95%CI = 0.950–1.364), P = 0.16]. Both groups showed comparable clinical pregnancy, ongoing pregnancy, miscarriage, multiple pregnancy, ectopic pregnancy and cumulative live birth rates. Limitations, reasons for caution Women with anticipated high ovarian responses were recruited and the results may not be extrapolated to the general population seeking IVF. This is not a blind study although the live birth rate as the primary outcome is objection. The duration of the study is 6 months since randomization. Wider implications of the findings In situations in which fresh embryo transfer is not required such as oocyte/embryo freezing for fertility preservation, oocyte donation or preimplantation genetic testing, the PPOS protocol may be preferred over the antagonist protocol. Trial registration number NCT04414761

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 &amp;lt; 0.001), had a higher antral follicle count (AFC) (20.79±8.66 vs. 14.12±9.96, p &amp;lt; 0.001), underwent OS with a lower gonadotropin dose (2036.25±766.20IU vs. 2715.20±976.40IU, p &amp;lt; 0.001) and triggered mostly with GnRHa (86.44% vs. 57.50%, p &amp;lt; 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 &amp;lt; 0.001), number of MII oocytes (12.05±5.97 vs. 7.42±5.91, p &amp;lt; 0.001), FORT (81.53±20.59% vs. 73.72±23.80%, p &amp;lt; 0.001) and FOI (95.49±48.78% vs. 76.31±47.60%, p &amp;lt; 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

P-642 The effect of oral dydrogesterone (DYD) on the hypothalamic-pituitary-ovarian (HPO) axis (gonadotropin and sex-steroid levels) and ovulation inhibition: a double-blind, phase I, randomized-controlled, parallel-group trial

Abstract Study question What is the effect of oral dydrogesterone (three cycles daily 20mg/30mg) on pituitary, ovarian and adrenal hormones, ovulation inhibition and endometrium in healthy ovulatory women? Summary answer Daily oral dydrogesterone, 20mg or 30mg, suppresses LH and inhibits ovulation in 33% and 73% of subjects, respectively, while not reducing E2 and other hormones. What is known already Dydrogesterone, a stereoisomer of progesterone, has high oral bioavailability and has demonstrated clinical utility in several indications, including endometriosis and assisted reproduction technologies. Progestin primed ovarian stimulation (PPOS) provides a cost effective and convenient alternative to the GnRH antagonist protocol to suppress a premature LH surge during ovarian stimulation in preparation for frozen embryo transfer IVF. In PPOS, studies have shown that dydrogesterone provides a comparable number of mature oocytes as a standard GnRH antagonist. The effects of various formulations and routes of administration of different progestins on sex hormones and the HPO has not been determined across the indications. Study design, size, duration A single-centre, double-blind, randomised, multiple-dose, parallel-group study of two doses of oral dydrogesterone over three 28-day treatment cycles: dydrogesterone 30mg, 10mg in the morning, afternoon and evening; dydrogesterone 20mg, afternoon dose replaced with placebo. The primary efficacy outcome was the number of subjects with “no ovulation at all” (Hoogland and Skouby score [HSS] 1-4) or “ovulation without pregnancy risk” (HSS 5-6 with negative Landgren criterion) recorded in all treatment cycles. Participants/materials, setting, methods The study population was 44 healthy, pre-menopausal women aged 18–35 years, with proven pre-treatment ovulation. The inclusion/exclusion criteria were defined to reflect the intended target population and the general contraindications for hormonal preparations. The primary objective was to compare the effect of the two self-administered doses of dydrogesterone on ovarian follicular growth leading to ovulation and E2 suppression. Secondary objectives included effect on other HPO hormones, the endometrium, PK characteristics and safety. Main results and the role of chance The number of responders to ovulation inhibition was dose-dependent: DYD 30mg, 72.7%, 95% CI: 49.78–89.27%; DYD 20mg, 33.3%, 95% CI: 14.59–56.97%. Based on HSS and Landgren criteria, there was 42.4% and 15.15% ovulation with pregnancy risk with the 20mg and 30mg doses, respectively. Neither dose had any clinically relevant influence on the average E2 concentration or FSH, androstenedione, dehydroepiandrosterone sulphate, testosterone and sex hormone binding globulin levels, while both doses suppressed the pre-ovulatory LH surge. Endometrial proliferation was mildly suppressed to a comparable extent with both daily doses. Hyperechogenic endometrium pattern was observed in 50% and 72% of treatment cycles in ovulating women in the 20mg and 30mg groups, respectively. Treatment with DYD did not significantly delay follicular growth or postpone ovulation in ovulating women. The more pronounced progesterone suppression with the higher 30mg dose may be due to the higher number of subjects without ovulation and thus without a post-ovulatory progesterone rise in that group. Return of ovulation after treatment cessation occurred in 91% women in the 42-day post-treatment period. The most frequently reported TEAE was ‘ovarian cyst’; all cases were of mild intensity and resolved at the end of the trial. No severe TEAE was reported. Limitations, reasons for caution Only two doses were studied in healthy, ovulatory women. DYD is used in various clinical contexts with concomitant other medications, such as gonadotropins for ovarian stimulation, or under luteotropic circumstances with human chorionic gonadotropin activity from exogenous or endogenous sources. Only limited morning PK sampling was performed. Wider implications of the findings Oral dydrogesterone used for endometriosis symptom reduction may be associated with a low risk of long-term adverse events from hypoestrogenism and suppression of androgens. Oral dydrogesterone displays relevant and short-term effects on LH levels, supporting its use in PPOS protocols. At therapeutic doses, dydrogesterone does not completely inhibit ovulation. Trial registration number EudraCT-No.: 2021-004747-24

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

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

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

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

P-656 Comparative clinical outcome following individualized follitropin delta dosing in Japanese women undergoing progestin-primed ovarian stimulation for in vitro fertilization /intracytoplasmic sperm injection

Abstract Study question Is ovarian stimulation with follitropin delta (FD) in its individualized regimen as efficacious as follitropin alfa and human menopausal gonadotropin (FAHMG)? Summary answer Ovarian stimulation with individualized FD dosing resulted in a significantly higher fertilization rate and number of blastocysts with good quality compared to conventional FAHMG dosing. What is known already Previous randomized controlled trials conducted in Japan, China, Europe, and both North and South America have demonstrated that ovarian stimulation using the individualized FD dosing regimen, which is based on serum anti-Müllerian hormone (AMH) levels and body weight, effectively modulated the ovarian response without compromising pregnancy and live birth rates. Study design, size, duration A retrospective study was conducted by reviewing the medical records of 1,720 IVF/ICSI cycles in 1,272 Japanese patients. The primary endpoint of the study was the ongoing pregnancy rate, assessed at 8 weeks of gestation, in the frozen-thawed embryo transfer. Participants/materials, setting, methods The FD treatment consisted of a fixed daily dose individualized according to each patient’s initial AMH level and body weight (AMH &amp;lt;2.04 ng/ml: 12 μg; AMH ≥2.04 ng/ml: 0.19 to 0.10 μg/kg; min-max 6–12 μg). The FAHMG dose was determined by the antral follicle count (AFC), with the following protocol: for AFC &amp;lt;25, 300 IU/day; for 40&amp;gt; AFC ≥25, 225 IU/day; and for AFC ≥40: 150 IU/day). A progestin-primed ovarian stimulation (PPOS) protocol was applied. Main results and the role of chance Multiple regression analyses (MRA) showed that the use of FD was negatively correlated with the number of oocytes retrieved (NOR) (P = 0.001), and positively correlated with the fertilization rate (FR) (P = 0.02). NOR was comparable between FD and FAHMG (10.9 ± 6.4 versus 11.8 ± 7.8) when the Mann-Whitney test (MW) was applied (P = 0.111), but significantly higher in FAHMG when the patient is younger than 40 years old with AMH ≥2 ng/ml (P &amp;lt; 0.01). The total gonadotropin use was significantly (P &amp;lt; 0.001) reduced from an average of 167.1 ± 46.9 μg (2789.9 ± 782.9 IU) FAHMG to 102.6 ± 31.6 μg FD. FR was significantly higher in FD compared with FAHMG (78.7% versus 74.1%, P &amp;lt; 0.05) on MW. Additionally, MW indicated a significantly higher number of good-quality blastocysts in FD (2.9±2.6) versus with FAHMG (2.4±2.5) (P &amp;lt; 0.05). The blastocysts obtained from FD also showed a significantly higher implantation rate (50.1% versus 39.7%, P &amp;lt; 0.01) and a comparable ongoing pregnancy rate (28.7% versus 25.7%, P = 0.292) compared to those from FAHMG as determined by chi-square test. The higher implantation rate in FD may be attributed to the greater number of good-quality blastocysts obtained compared with FAHMG. Limitations, reasons for caution This study only covered the clinical outcome of women undergoing PPOS protocol with frozen-thawed blastocyst transfers. Wider implications of the findings The present study shows that FD in its individualized fixed-dose regimen has the potential to improve the success rate in frozen-thawed embryo transfer across all ages and with a lower gonadotropin consumption compared to conventional FAHMG dosing. Trial registration number not applicable

P-594 Retrospective comparative study of follitropin delta vs follitropin alfa in progestin-primed ovarian stimulation (PPOS) protocol in IVF

Abstract Study question Could the individualized fixed-dose algorithm with follitropin delta show a similar pregnancy rate to conventional dosing with follitropin alfa in PPOS protocol? Summary answer Individualized fixed-dose algorithm with follitropin delta showed a similar pregnancy rate to follitropin alfa In PPOS protocol. What is known already Follitropin delta (REKOVELLE, Ferring Pharmaceuticals, Switzerland) is the first human cell line driven recombinant follicle-stimulating hormone (FSH) with an individualized fixed-dose algorithm based on serum AMH level and body weight. Follitropin alfa is a Chinese hamster ovarian cell driven recombinant FSH and its dosing is adjusted according to follicular response during the stimulation period. There was no significant difference between follitropin delta and follitropin alfa in terms of pregnancy rate under GnRH antagonist protocol. Study design, size, duration A retrospective analysis of 355 patients aged under 40 years who underwent ovarian stimulation in PPOS protocol using follitropin delta or follitropin alfa and on whom frozen-thawed single blastocyst transfer was conducted between August 2021 and November 2023 was performed. Participants/materials, setting, methods 193 cycles of women who used follitropin delta were compared to 162 cycles of women who used follitropin alfa. The following clinical outcomes on each treatment group were analyzed: chemical pregnancy rate (serum β hCG), clinical pregnancy rate (gestational sac), ongoing pregnancy rate(gestational sac and fetal heartbeat), serum E2 level at trigger day, cycle proportion of ≥ 10 oocytes retrieval, blastocyst formation rate, cycle proportion of ≥ 5 blastocysts and cycle proportion of ≥ 2 good quality blastocysts. Main results and the role of chance Baseline demographics in the follitropin delta group and the follitropin alfa group were not significantly different: age, 33.9 ± 3.5 years vs 34.5 ± 3.2 years; body weight, 53.5 ± 8.3 kg vs 53.8 ± 5.9 kg; number of previous IVF cycles, 0.2 ± 0.6 vs 0.3 ± 0.7; serum AMH level, 5.5 ± 2.9 ng/mL vs 5.3 ± 3.8 ng/mL, respectively. The chemical pregnancy rate (69.9% vs. 64.8%, P = 0.308), clinical pregnancy rate (58.0% vs. 56.2%, P = 0.748) and ongoing pregnancy rate (51.8% vs. 46.3%, P = 0.338) were comparable between the follitropin delta group and the follitropin alfa group. The individualized follitropin delta treatment resulted in a smaller cycle proportion of ≥ 10 oocytes retrieval (77.7% vs. 90.8%, P &amp;lt; 0.001) with lower serum E2 level at trigger day (3273 ± 1577 pg/mL vs. 3927 ± 1732 pg/mL, p &amp;lt; 0.001). However, the blastocyst formation rate was significantly higher in the follitropin delta group (75.5% vs. 68.7%, p &amp;lt; 0.001). Moreover, the cycle proportion of ≥ 5 blastocysts (71.0% vs. 76.4%, P = 0.286) and the cycle proportion of ≥ 2 good quality blastocysts (51.8% vs. 60.3%, P = 0.115) were comparable between the groups. Limitations, reasons for caution This is a non-controlled, retrospective study. Wider implications of the findings Follitropin delta in its individualized fixed-dose regimen could have the potential to decrease the risk of OHSS by minimizing excessive ovarian response, whereas a similar pregnancy rate to conventional dosing regimen could be expected due to the number of good quality blastocysts secured. Trial registration number not applicable

P-549 Differentially expressed genes in the immune cells obtained from preovulatory follicles undergoing progestin-primed ovarian stimulation and GnRH-antagonist: Insights from single-cell RNA sequencing analysis

Abstract Study question Could controlled ovarian stimulation protocol (progestin-primed ovarian stimulation [PPOS] vs GnRH-antagonist [GnRH-ant]) affect the gene expression of human immune cells (ICs) in preovulatory follicles? Summary answer Proinflammatory cytokine-related gene expression was significantly higher and proinflammatory pathways were also more prominently involved in ICs in PPOS than the GnRH-ant. What is known already PPOS has garnered attention, with several studies suggesting reproductive outcomes comparable to GnRH-ant. However, in our previous study, pregnancy outcomes with PPOS were significantly lower than GnRH-ant (38th ESHRE Annual Meeting [O-130]) and single-cell RNA sequencing (scRNA-seq) of granulosa cells revealed increased mitochondrial DNA gene expression in PPOS than GnRH-ant (39th ESHRE Annual Meeting [P-281]). Previous studies suggested that ICs play a pivotal role in follicular and embryonic developments, via proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. Notably, changes in gene expressions of ICs under different controlled ovarian stimulation (COS) protocols remain unresolved to date. Study design, size, duration From November 2021 to January 2022, all samples were obtained from the patients who provided written informed consent before the inclusion and underwent COS cycles at a single-institution. scRNA-seq was performed on 6,828 cells corresponding to ICs of the MII-oocyte follicles (56 from PPOS and 39 from GnRH-ant), involving 16 patients with normal ovarian reserves (aged &amp;lt; 40 years, AMH ≥1.1 ng/mL) undergoing PPOS with chlormadinone acetate (n = 8) or GnRH-ant with cetrorelix (n = 8). Participants/materials, setting, methods The ICs were collected via follicular aspiration from 16 patients. The follicular fluid (FF) from each follicle was collected and all FF were mixed together in MII-oocyte for sequencing. Sample sequencing was performed using Chromium Next GEM Single Cell V(D)J Reagent Kits (10X Genomics, Pleasanton, CA, USA). Libraries were sequenced using a DNBSEQ-G400, with reads subsequently analyzed using Cellxgene. The clustering was performed using fastcluster in scDblFinder. Functional enrichment analysis was carried out using Enrichr. Main results and the role of chance Two population of ICs were used in this investigation: PPOS and GnRH-ant of MII-oocyte. After the quality control, 4,447 cells for PPOS and 2,381 cells for GnRH-ant, respectively, were analyzed. Following single-cell clustering based on the Seurat package, cell proportion analysis revealed eight clusters, which consist of monocyte, myeloid dendritic cell, T cell, natural killer cell and naive B cell, in the PPOS and GnRH-ant groups. No significant difference was observed in gene expression and cell distribution in each cluster. Differentially expressed genes (DEGs) were identified in the two IC population. Interestingly, a significant increase in expression of proinflammatory cytokine including IL-1β and IL-6 was observed in PPOS compared to GnRH-ant, particularly in CD14-positive monocytes. Functional significance of DEGs was validated by identifying significantly regulated pathways based on Kyoto Encyclopedia of Genes and Genomes categories, revealing involvement in TNF signaling, IL-17 signaling, and NF-κB signaling pathways. Limitations, reasons for caution Our conclusions are limited due to the inclusion of Japanese patients at a single-institution. The results need to be validated across different centers and other ethnicities. Due to the small sample size, these results should prompt further study to confirm our findings. Wider implications of the findings This is the first report assessing the DEGs of ICs under different COS protocols at the single-cell level. This study suggests that progestin for PPOS induces elevation of the proinflammatory cytokine gene expression of ICs in preovulatory follicles, which may be associated with reproductive outcomes. Trial registration number Not applicable