Cyclic Hormone Replacement Therapy Research Articles

Intrauterine Infusion and Hysteroscopic Injection of Autologous Platelet-Rich Plasma for Patients with a Persistent Thin Endometrium: A Prospective Case–Control Study

Objectives: To evaluate the effect of intrauterine infusion and hysteroscopic injection of autologous platelet-rich plasma (PRP) in patients with a persistent thin endometrium (EM) undergoing euploid frozen embryo transfer (EFET) cycles. Methods: This prospective case–control study enrolled 116 infertile women with thin EM (<7 mm) who underwent hormone replacement therapy (HRT) for EFET. These women had experienced at least one previous unsuccessful EFET cycle, which either resulted in the cancellation of the cycle or failure of pregnancy. A total of 55 women received an intrauterine infusion of PRP before FET, 38 received a hysteroscopic injection of PRP, and 23 received standard HRT treatment without PRP (control group). Only euploid embryos were transferred in these cycles. The primary outcomes were the implantation rate (IR) and clinical pregnancy rate (CPR) after EFET. Results: After receiving intrauterine infusion and hysteroscopic injection of PRP, 78.2% and 55.3% of patients, respectively, showed an EM thickness exceeding 7 mm, followed by embryo transfer. The hysteroscopic injection group demonstrated significantly higher IR (52%), a higher trend of CPR (52%), and a higher live birth rate (38%) than the control group (18%, 22%, and 4%). Conclusions: Intrauterine infusion and hysteroscopic injection of autologous PRP may be effective methods to increase EM thickness in HRT cycles. According to our results, both methods could increase EM thickness, while hysteroscopic injection appeared to provide more significant assistance in increasing IR, CPR, and live birth rate after EFET in patients with persistent thin EM.

Resistant ovary syndrome: Two case reports and a literature review of effective controlled ovarian stimulation in IVF.

Resistant ovary syndrome (ROS) represents a rare reproductive endocrine disorder that is predominantly associated with infertility, characterized by heightened endogenous gonadotropin levels in the presence of a normal ovarian reserve. Patients with ROS typically exhibit a poor response to exogenous gonadotropins during controlled ovarian stimulation (COS). Due to the absence of a universally accepted effective COS protocol, this study aims to contribute to the existing body of literature by detailing 2 successful pregnancies achieved through conventional in vitro fertilization (c-IVF) in patients with ROS, and through retrospective analysis, seeks to elucidate the factors contributing to the successful ovarian stimulation in these cases, with the ultimate goal of establishing clinical guidelines for ROS management. The central challenge addressed in this study pertains to the effective induction of oocyte maturation during c-IVF COS in ROS patients. The study focuses on 2 infertile women diagnosed with ROS who sought to conceive via c-IVF. The patients were subjected to a COS protocol involving pituitary downregulation followed by ovarian stimulation using recombinant follicle-stimulating hormone (r-FSH) and human menopausal gonadotropin (HMG), preceded by 3 cycles of hormone replacement therapy (HRT) pretreatment. The proposed protocol elicited a favorable ovarian response, culminating in the retrieval of numerous mature oocytes and the development of multiple viable embryos via c-IVF, ultimately leading to successful live births post-embryo transfer. Our study suggests that the outlined COS protocol may serve as a viable treatment option for ROS patients aspiring to conceive through c-IVF, thereby potentially expanding the therapeutic repertoire for this challenging condition.

Evaluating the Impact of Long-Term GnRH Agonist Therapy on Pregnancy Outcomes in Endometriosis-Associated Implantation Failure and Pregnancy Loss

Purpose This study aimed to investigate the efficacy of long-term gonadotropin-releasing hormone (GnRH) agonist therapy in preventing endometriosis progression and relieving symptoms, particularly on pregnancy outcomes during thawed embryo transfer in patients experiencing endometriosis and recurrent implantation failure or recurrent pregnancy loss. Methods In individuals with clinical endometriosis and a history of recurrent implantation failure or recurrent pregnancy loss, we conducted a comparative analysis of clinical outcomes between those undergoing long-term GnRH agonist treatment for symptom relief, such as menstrual pain, followed by embryo transfer using Hormone Replacement Therapy (HRT) cycle, and those undergoing embryo transfer using an HRT cycle without GnRH agonist treatment. The study examined various clinical outcomes between the two groups. Results The primary outcomes included live birth rate (LBR), miscarriage rate, biochemical pregnancy rate, and perinatal complications. The GnRH agonist group showed significantly higher LBR than the control group (37.50% vs. 13.04%; p=0.02). Multivariable logistic regression analysis, adjusted for age and gravidity, showed significantly higher LBR in the GnRH agonist group compared to the control group (odds ratio: 15.3; 95% confidence interval: 2.30, 102.00; p=0.005). Conclusions The findings of this study suggested that employing a GnRH agonist in the embryo transfer protocol is effective for patients with endometriosis experiencing recurrent implantation failure or recurrent pregnancy loss.

A retrospective comparative study of double cleavage-stage embryo transfer versus single blastocyst in frozen-thawed cycles

BackgroundThis retrospective study aimed to compare the outcomes of day 3 double embryo transfer (DET) with single blastocyst transfer (SBT) during frozen embryo transfer (FET) cycles. A total of 999 women below the age of 38 years who underwent FET at Malaysia’s KL Fertility and Gynaecology Centre from January 2019 to December 2021 were analyzed. Patients with autologous eggs were recruited in the study. All the eggs were inseminated by intracytoplasmic sperm injection. The embryos were vitrified on day 3 cleavage-stage or blastocyst stage with Cryotop® method. The FET was performed following natural cycle (NC), modified natural cycle (m-NC), or hormone replacement therapy (HRT) cycles. The NC and m-NC groups received oral dydrogesterone for luteal phase support.ResultsThere were no statistical differences in the rates of positive pregnancy, clinical pregnancy, and ongoing pregnancy between the two groups. However, implantation rates were significantly higher in the SBT group (50.1% versus 37.6%, p < 0.05). The day 3 DET group had significantly higher multiple pregnancy rates (28.7% versus 1.1%, p < 0.05). Subgroup analysis of embryo transfers performed following NC, m-NC, or HRT cycles showed similar results.ConclusionsThis study suggests that SBT is the better choice for embryo transfers as it had higher implantation rates and its pregnancy rates were similar to day 3 DET. The SBT also significantly reduced the incidence of multiple pregnancies without compromising pregnancy rates.

#384 : Effectiveness of Progesterone Monitoring and Rescue Protocol in Frozen Embryo Transfer Cycle

Background and aim: Hormonal monitoring impact on overall pregnancy rate in frozen embryo transfer (FET) cycles and hence progesterone supplement adjustments remain debatable in current literature. This study aims to investigate the effect of monitoring and follow-up of serum progesterone level on the day of FET, and progesterone supplement adjustments effects on pregnancy outcomes for FET in programmed hormonal replacement therapy cycles. Methods: In this study, all patients who were scheduled for FET had their progesterone (P4) and estradiol (E2) level assessed in the morning of FEM and if their P4 level was less than 10 ng/ml, intramuscular progesterone was given for 7-10 days since the day of FET to rescue the cycle. Results: In 2022, in Vinmec IVF center, there were in total 659 FET cycles, all was single blastocyst transfer and applied the mention protocol to rescue the cycle in case P4 level was less than 10 ng/ml. The chemical (62,87% vs 59.94%), clinical (56,68% vs 54,83%) and ongoing pregnancy rate (46,25% vs 45,17%) were comparable between the two group (with and without parenteral progesterone), P&lt;0,05. Conclusions: Monitor P4 level on the day of FET and use parenteral progesterone in case P4 level is less than 10 ng/ml could be an effective method to rescue the cycle and improve the outcome. Further studies are needed to draw a better conclusion and recommendation in this aspect.

The effects of different endometrial preparation regimens on pregnancy outcomes in frozen-thawed embryo transfer cycles: a prospective randomized controlled study

Objective An increasing number of research have emerged to compare the pregnancy outcomes between the natural cycle and the hormone replacement therapy (HRT) cycle in preparing the endometrium for frozen-thawed embryo transfer (FET), but the results are controversial. This prospective randomized controlled study was hence designed to obtain more solid evidence. Materials and methods In this study, patients with regular menstrual cycle length (21–35 days) who underwent FET between January 2010 to December 2017 were recruited for this study. Upon further filtering with the selection criteria of patients being, a total of 405 patients were recruited and randomized. Finally, analysis was performed on 384 patients: 178 belonged to the natural cycle group whereas the remaining 206 were in the HRT group. The primary outcome was live birth rate, while the secondary outcomes were implantation rate, clinical pregnancy rate, early miscarriage rate, late miscarriage rate, multiple birth rate and low birth weight rate. Results The live birth rate (37.6% vs 30.1%, p = 0.119) of natural cycle group were higher than those of the hormone replacement therapy group, although the difference was not significant. The secondary outcomes were not found to differ significantly between the two groups. Nonetheless, the endometrium was found to be thicker in the natural cycle group (10.75 mm) than the HRT group (9.00 mm) (p < 0.001). Conclusion No significant differences were observed between the pregnancy outcomes of the natural cycle group and the HRT group which comprised of patients with regular menstrual cycle length.

Letrozole use in vitrified single-blastocyst transfer cycles is associated with lower risk of large for gestational age infants in patients with polycystic ovary syndrome.

To evaluate the obstetric and perinatal outcomes of three routine endometrial preparation protocols in women with PCOS who underwent frozen embryo transfer (FET). This was a retrospective study in women with PCOS who underwent FET in an academic reproductive medical center. A total of 2710 cycles were enrolled and classified into three groups according to different endometrial preparation protocols; human menopausal gonadotropin (HMG), letrozole + HMG, or hormone replacement therapy (HRT). The stimulation groups had reduced risks of hypertensive disorders of pregnancy (HDP), large for gestational age (LGA) infants, and cesarean delivery than the HRT group. After adjustment for different confounder combinations in the two models, the frequencies of LGA and HDP in the letrozole + HMG group and the HMG group were still significantly lower than those in the HRT group. The letrozole + HMG group exhibited a reduced risk of LGA than HMG group after adjustment of confounders. A trend toward risk reductions in HDP and LGA was observe in turns of HRT, HMG, and letrozole + HMG groups, and the trends were statistically significant (Ptrend = 0.031 and 0.001). In patients with PCOS, ovarian stimulation protocols for endometrial preparation are associated with reduced risks of HDP and LGA compared to HRT cycles. The use of letrozole could further reduce risk of LGA compared to HMG only protocol. We propose that ovarian stimulation protocols can be used widely for endometrial preparation in FET cycles in women with PCOS, especially with the use of letrozole.

Clinical efficacy of hysteroscopic adhesiolysis combined with periodic balloon dilation for intrauterine adhesion in IVF treatment.

Intrauterine adhesions (IUA), arising from diverse etiological factors, pose a significant threat to female fertility, particularly during in vitro fertilization (IVF) treatment. To assess the effectiveness of hysteroscopic adhesiolysis (HA) combined with periodic balloon dilation in treating IUA and its impact on reproductive outcomes in women undergoing IVF treatment. A total of 234 patients diagnosed with IUA were included in this study. The IUA women were categorized into three subgroups based on the severity of adhesion. All IUA patients underwent HA separation followed by periodic balloon dilation along with hormone replacement therapy (HRT). Frozen embryo transfer was performed post-treatment, and a comparative analysis of the general characteristics and clinical outcomes among the subgroups was conducted. The control group consisted of patients who underwent their first embryo transfer of HRT cycle without any uterine abnormalities, as assessed by the propensity score matching (PSM). The clinical outcomes of IUA group and control group were compared. Multivariate logistic regression analyses were employed to investigate the risk factors associated with live birth. ① The endometrial thickness was significantly increased post-operation compared to pre-operation in all three IUA subgroups (all P <0.001), with the most pronounced change observed in the severe IUA group. After treatment, normal uterine cavity was restored in 218 women (93.16%). ② The overall clinical pregnancy rate was 49.57% (116/234) and live birth rate was 29.91% (70/234). The clinical outcomes were similar among the three subgroups after first embryo transfer (all P>0.05). Multivariate logistic regression analyses revealed that age (aOR 0.878, 95% CI 0.817~0.944, P=0.001) and endometrial thickness after treatment (aOR 1.292, 95% CI 1.046~1.597, P=0.018) were the two significant risk factors for live birth rate. ③ Following the process of matching, a total of 114 patients were successfully enrolled in the control group. The baselines and the clinical outcomes were all comparable between the IUA group and control group (all P>0.05). The combination of HA and periodic balloon dilation is beneficial for improving endometrial receptivity and has a significant clinical impact on patients with IUA undergoing IVF.

Retrospective analysis of the endometrial preparation protocols for frozen-thawed embryo transfer cycles in women with endometriosis

BackgroundThere was inconsistency in optimal endometrial preparation protocol for frozen-thawed embryo transfer (FET) in patients with endometriosis. We conducted this study to investigate the effect of different endometrial preparation protocols on the pregnancy outcomes in patients with endometriosis undergoing FET cycles, and determine the optimal number of GnRHa injections in GnRHa-HRT protocols.Method(s)This was a retrospective cohort analysis of women with endometriosis who underwent FET cycles at a single university-based center. This study retrospectively analyzed 2048 FET cycles in our center from 2011 to 2020. According to the endometrial preparation protocols, patients were divided into 4 groups: gonadotropin releasing hormone agonist-hormone replacement therapy(GnRHa-HRT), hormone replacement therapy(HRT), ovulation induction(OI), and natural cycle(NC). In the GnRHa-HRT group, patients were further divided into 3 groups: one injection of GnRHa, two injections of GnRHa, and three or more injections of GnRHa. The primary outcome was the clinical pregnancy rate. Propensity score matching was used to adjust for potential non-similarities among the groups. Multivariate logistic regression analysis was performed to figure out the risk factors for pregnancy outcomes.Result(s)There were no statistical differences in pregnancy outcomes among the four endometrial preparation protocols in FET cycles with endometriosis patients, the results retained after propensity score matching(PSM). And in endometriosis patients complicated with adenomyosis, the results remained similar. In patients with GnRHa-HRT protocol, there were no differences in clinical pregnancy rate and live birth rate with different numbers of GnRHa injections, the early miscarriage rate were 18% in the two injections of GnRHa group and 6.5% in the one injection of GnRHa group(P = 0.017). Multifactorial logistic regression analysis showed that two injections of GnRHa before FET was associated with increased early miscarriage rate compared with one injection of GnRHa[adjusted OR (95% CI): 3.116(1.079–8.998),p = 0.036].Conclusion(s)The four kinds of endometrial preparation protocols for FET, GnRHa-HRT, HRT, OI and NC had similar pregnancy outcomes in patients with endometriosis. In endometriosis patients complicated with adenomyosis, the results remained similar. In patients with endometriosis undergoing GnRHa-HRT protocol for FET, more injections of GnRHa had no more advantages in pregnancy outcomes, on the contrary, it might increase the early miscarriage rate.

Duration of oestrogen exposure does not affect reproductive outcome in artificial cycles: a retrospective analysis of more than 7000 hormonal replacement therapy cycles for an embryo transfer.

Optimal duration of oestrogen exposure before an embryo transfer in artificial cycles has not been defined yet, as its correlation with reproductive outcome remains controversial. The length of oestrogen treatment before starting luteal phase support varies significantly among patients. In this study, we conducted a retrospective analysis of a huge database of our own clinical results in artificial cycles in the past five years. The aim of this study was to assess the effect of the length of estrogen exposure on reproductive outcome and to evaluate if there is any optimal duration of estrogen exposure in order to maximize success rates. Differences in pregnancy rates according to oestrogen length, if present, were not clinically relevant. Our results suggest that the length of oestrogen exposure (in days) before exogenous progesterone administration do not affect clinical outcomes.

P-500 Relationship of midluteal serum progesterone levels and pregnancy outcomes after day-3 embryo-transfer(ET) in hormonal replacement therapy (HRT) cycles with intramuscular progesterone: a prospective cohort study

Abstract Study question Does midluteal(day-9 of progesterone) serum progesterone level in HRT cycles with intramuscular progesterone affect the clinical pregnancy rate (CPR)/early miscarriage rate(MR) and live birth rate(LBR)? Summary answer Midluteal serum progesterone between 32.2-43.7ng/ml results in significantly greater CPR versus that with lower/higher levels and significantly greater LBR compared to that with lower levels. What is known already Evidence points to low serum progesterone levels at the time of FET being associated with lower ongoing pregnancy rates. Recently, the relation of midluteal serum progesterone levels in HRT cycles with vaginal progesterone as luteal phase support (LPS) has been elaborated indicating better pregnancy outcomes with an optimum range of serum progesterone/higher levels. There is no data establishing the association of pregnancy outcomes with midluteal serum progesterone levels when intramuscular progesterone is used as LPS in HRT cycles. Study design, size, duration A prospective cohort study conducted between December 2019-March 2022 at a tertiary centre with 196 patients(204 cycles), both-autologus(AO)-56.3% and donor oocytes(DO)- 43.6%: fresh ET-16.6% and frozen ET(FET)-83.3% with similar ICSI, vitrification and ET protocols(2/3 Grade A day-3 embryos). CPR, early MR (≤13 weeks miscarriage/clinical pregnancy) and LBR (≥28 weeks, LBs/ETs) were compared. Serum progesterone was measured on the morning of day-5 post-ET(day 9th from the start of progesterone). Most patients delivered at the same institute. Participants/materials, setting, methods Patients were non-smokers with normal hysteroscopy. Oral estradiol 6-8mg was initiated from Day 1-2 (for 10-17 days). When ET ≥ 7mm and serum progesterone &amp;lt;1ng/ml, intramuscular progesterone 100mg/day was started (daily till day-4 post-ET, then every 3rd day till week 8). Vaginal progesterone gel was added from day 5 post-ET till week 10. Serum progesterone levels were categorized in tertiles. Chi-square, t-tests and multiple regression analysis was used for statistical analysis. Two-tailed P&amp;lt;.05 indicated statistical significance. Main results and the role of chance Mean age was 34.76±5.36 years with a mean BMI 26.4±4.38kg/m2 Overall, CPR was 106/204(51.9%), LBR 78/204(38.2%) and early MR 28/106(26.4%) Midluteal serum progesterone levels ranged from 11.1-261ng/ml and were divided into tertiles(T) T1&amp;lt;32.0ng/ml(n = 68),T2 32.2-43.7ng/ml(n = 68),T3 &amp;gt;43.7ng/ml (n = 68) Median progesterone levels of T1,T2,T3 were 27.7ng/ml(Interquartile range [IQR] 7.0), 38.4ng/ml (IQR 5.0) and 51.2ng/ml (IQR 12.6) respectively. Mean age and mean BMI was not significantly different across the tertiles P=.27, P=.20 respectively CPR was significantly different across T1 32/68(47%),T2 45/68(66.1%)and T3 29/68(42.6%) P=.014. CPR was significantly more in T2 versus T1 and T3, (OR:2.2, 95%CI:1.1-4.4 P =.02) and (OR:2.6,95%CI:1.3-5.3, P=.006), respectively. T3 versus T1, P =.60 LBR was also significantly different across the tertiles [T1 20/68(29.4%), T2 34/68(50%),T3 24/68(35.3%) P=.03] LBR in T2 was significantly more than in T1(OR: 2.4,95% CI:1.2-4.9, P=.02). There was no significant difference betweenT3 versus T1 and T2 versus T3, P=.46, P=.08, respectively. Early MR wasn’t significantly different across T1 12/32(37.5%), T2 11/45(24.4%) and T3 5/29(17.2%), P=.18 Serum progesterone levels were not significantly affected by age r = 0.0257, P=.71 or BMI r = 0.0097, P=.89 Multivariate logistic regression showed that age affected CPR after adjusting for BMI, midluteal serum progesterone levels, origin of oocytes, fresh ET/FET(AOR 0.92: 95% CI:0.86-0.98, P=.01). Limitations, reasons for caution This is a single centre study with limited sample size. Including the measurement of serum progesterone at the time of ET would have given a better perspective of the patient specific behavior of progesterone as LPS. Larger studies with different LPS protocols are needed to validate the results. Wider implications of the findings In HRT cycles with intramuscular progesterone, an optimum midluteal serum progesterone level is related to better pregnancy outcomes. Factors causing the wide variation of progesterone levels need to be evaluated so as to individualize the dose. Identifying the appropriate time frame for optimising the midluteal progesterone levels should be explored. Trial registration number not applicable

P-491 The efficacy of subcutaneous versus vaginal progesterone for luteal phase support - a comparison in 723 blastocyst hormone replacement therapy frozen embryo transfer cycles

Abstract Study question Are ongoing pregnancy rates (OPRs) similar between subcutaneous (sc) progesterone (P) and vaginal P administration in hormone replacement therapy (HRT) frozen embryo transfer (FET) cycles? Summary answer The OPRs were similar between sc and vaginal P administration; however, 15.8% of patients in the vaginal group needed additional P as rescue therapy. What is known already There is a paucity of data comparing sc and vaginal P administration in HRT-FET cycles. In HRT-FET cycles, there seem to be marked interpersonal differences in serum progesterone (P4) levels following the same dose and route of P administration. Impaired reproductive outcomes have been reported when serum P4 levels are below a certain threshold (10 ng/ml) on the FET/FET-1 day; rescue with supplemental sc P in these cases might rectify reproductive outcomes. With sc P, only one study reported comparable OPRs in four quartiles of serum P4 on the day of FET in HRT cycles. Study design, size, duration A cohort study was conducted during December 2019-November 2022, including a total of 723 consecutive warmed blastocyst transfer cycles, employing HRT. Each patient was included only once. The inclusion criteria were female age ≤44 years old, BMI ≤40 kg/m2, and having available day-5/6 vitrified blastocyst(s) after warming. Pre-implantation genetic testing cycles for aneuploidy (PGT-A) were included, whereas PGT for monogenic disorders/structural re-arrangements and the presence of uterine anomalies were excluded from the study. Participants/materials, setting, methods Following estrogen priming, sc P 25 mg twice-daily (n = 249) or vaginal P gel 90 mg twice-daily (n=474) were administered. The serum P4 level was measured on the FET-1 day, i.e., day 5 of P supplementation. In patients with serum P4 levels &amp;lt;8.75 ng/ml on the FET-1-day, additional exogenous sc P, 25 mg/day (rescue), was provided. The primary outcome measure was OPR. A generalized additive model was performed to study functional relationships between P4 and OPR. Main results and the role of chance The mean circulating P4 levels on the FET-1 day were 26.1 ± 8.1 ng/ml and 13.8 ± 5.5 ng/ml in the sc P and vaginal P gel groups, respectively (p &amp;lt; 0.001). In the vaginal P group, 15.8 % of patients needed sc P rescue, whereas no patient required rescue in the sc P group. All unadjusted reproductive outcome measures, including positive hCG per embryo transfer, implantation, clinical pregnancy, pre-clinical loss, miscarriage rates, and OPRs, were comparable between the sc P and vaginal P gel groups. After P rescue, when logistic regression analysis was performed to delineate the independent predictor(s) of ongoing pregnancy, only female age, number of blastocysts transferred, blastocyst morphology, and PGT-A were found to be the significant predictors. Importantly, sc P administration, necessitating no rescue, provided similar OPRs (adjusted OR = 1.22 95% CI:0.87-1.80) compared to vaginal P, in which rescue was needed in 15.8% of the patients. The impact of serum P4 levels on adjusted reproductive outcome measures was evaluated by percentiles (&amp;lt;10th, 10–49th, 50–90th, and &amp;gt;90th percentiles). All serum P4 percentiles had similar OPRs, and no significant association was observed between serum P4 levels and OPRs in both sc and vaginal P (with rescue if needed) groups. Limitations, reasons for caution Cohort study, lack of cost and side-effect analyses. Wider implications of the findings Subcutaneous P 25 mg twice-daily secures a serum P4 above 8.75 ng/ml, whereas additional exogenous P (rescue) was needed in 15.8% of patients receiving vaginal P administration only. The OPR was similar between the sc P alone and vaginal P groups after sc P rescue of the vaginal group. Trial registration number Not applicable

P-528 Intra-individual variability of serum progesterone level on the day of frozen blastocyst transfers in hormonal replacement therapy cycles

Abstract Study question Is there a significant intra-individual variability of serum progesterone level on the day of theHormone Replacement Therapy Frozen Embryo Transfer(HRT-FET) between two consecutive cycles? Summary answer No significant intra-individual variability of progesterone level measured the day of transfer was shown between two consecutive HRT-FET cycles. What is known already In frozen embryo transfer under HRT, a minimum P level around the day of embryo transfers necessary to optimize reproductive outcomes. Indeed, in a previous study, we have found that women with a serum P level ≤9.8ng/ml on the day of the single autologous blastocyst transfer had lower live birth rate. Moreover, some clinical factors have been described as influencing the P level on the day of the embryo transfer (i.e weight, gravidity, Ethnic origin,tobacco consumption…). Variations between patients raise the question of intra-individual variation in P measurement, in addition to the existence of inter-individual variation. Study design, size, duration We conducted an observational cohort study at the university-based reproductive medicine centre of our institution that focusing on women who underwent at least two consecutive single autologous HRT-FET of blastocyst, between January 2019 and March 2020. Participants/materials, setting, methods Patients undergoing two consecutive single autologous blastocyst HRT-FET using exogenous estradiol and vaginal micronized progesterone for endometrial preparation were included.The serum progesterone level was measured in the morning of the FET, in a single laboratory. The two progesterone measurements performed the day of the first (FET1) and the second FET (FET2) were compared to evaluate the intra-individual variability of serum P.Paired statistical analyses were performed, as appropriate. Main results and the role of chance Two hundred and sixty-four patients undergoing two consecutive single autologous blastocyst HRT-FET were included. The mean age of the included women was 35.0 ±4.2 years old. No significant intra-individual variability was observed between FET 1 and FET2 (Mean progesterone level after FET1: 13.4±5.1ng/ml versus after FET 2: 13.9±5.0; p = 0.08).Characteristics of embryo transfers were similar between the first and the second FET. Forty-nine patients (18.6%) had discordant progesterone levels (defined as one progesterone measurement &amp;gt; and one ≤ to the threshold of 9.8ng/ml) between FET1 and FET2. 37/264(14%) women had a high intra-individual variability (defined as a difference in serum progesterone values &amp;gt;75 e percentile (6.0ng/ml)) between FET1 and FET2. No specific clinical parameter was associated with a high intra-individual variability nor a discordant P measurements. Limitations, reasons for caution This study is limited by its retrospective design. Likewise, only women who underwent autologous blastocyst HRT-FET with micronized vaginal P were included. Wider implications of the findings No significant intra-individual variability was showed and the serum progesterone level seems to be reproducible in more than 80% of case. This study suggests that the serum progesterone level measured the day of the first transfer could be used to individualize luteal phase support on subsequent cycles. Trial registration number not applicable

P-614 Endometrial preparation: effect of estrogen levels before the embryo transfer on the live birth rate from 14825 freezing-all cycles

Abstract Study question Is there a difference in live birth rate during discrepant estrogen levels before the embryo transfer following either hormone replacement therapy (HRT) or natural cycle(NC)? Summary answer The higher estrogen level on the day before embryo transfer may reduce the live birth rate in either HRT or NC. What is known already The endometrial preparation of frozen embryo transfer cycle is to synchronize of endometrium and embryo under the condition of exogenous estrogen and progesterone drugs in HRT or follicle monitoring in NC. Estrogen is crucial and different estrogen levels could imply variations on endometrial preparation. Information on the effect of discrepant estrogen levels before the embryo transfer on reproductive outcomes of women undergoing freezing-all cycles is scarce. Study design, size, duration Retrospective cohort study including 14825 first frozen embryo transfers following IVF/ICSI undergoing freezing-all cycles from January 2016 to December 2020. A total of 12305 (83.0%) patients received NC while 2520 (17.0%) received HRT. Participants/materials, setting, methods Effect of estrogen levels on live birth rates, stratifified by deciles and ROC to determine the cutoff values for estrogen level on the day before embryo transfer.Multivariable logistic regression analysis was performed to adjust for confounders. Main results and the role of chance The live birth rate was 44.7% and 52.4% in HRT and NC respectively. The live birth rate of HRT began to decline when the estrogen level was P60 in the deciles which the cut-off values of ROC was closed with the estrogen level was 891.6 pg/ml. The lower level of estrogen on the day before embryo transfer in HRT corresponds to a higher live birth rate（51.4% vs 32.9%）.The cut-off values of ROC in NC was statistically different with the estrogen level was 194.4 pg/ml. The lower level of estrogen on the day before embryo transfer in NC corresponds to a higher live rate（53.0% vs 48.6%）.After adjusting the possible confounding factors by multivariate logistic regression, it was found that the estrogen level on the day before embryo transfer in HRT and NC was the independent influencing factor of live birth rate with the OR of 0.57 (0.47,0.68) and 0.82 (0.74,0.90), respectively. Limitations, reasons for caution The greatest limitation of this study is its retrospective study. On the other hand, this study was performed using non-PGT cycle, although this is unlikely to affect the results,we cannot exclude the possibility that euploid embryo responds differently to endometrial state in comparison to aneuploid embryo. Wider implications of the findings In freezing-all cycles, the higher estrogen level on the day before embryo transfer may reduce the live birth rate in either HRT or NC. Clinicians should pay attention to the control of estrogen level in luteal phase. Trial registration number Nona

P-636 Euploid blastocysts obtained in advanced maternal age women either in donor or autologous egg cycles showed similar live birth rates: a retrospective cohort study

Abstract Study question Do euploid blastocysts have the same implantation and live birth rate in autologous and donor egg cycles in patients with advanced maternal age (AMA)? Summary answer Euploid blastocysts transferred in AMA patients showed that implantation and live birth rates (LBR) were not significantly different between reproductively younger and older women. What is known already Aneuploidy rates increase steadily with age, reaching &amp;gt;80% in women &amp;gt;42 years old. The high prevalence of aneuploidies may provide an explanation for the low LBR achieved by assisted reproductive treatments, especially for women with AMA. Similarly, among oocyte donors, age is critical to achieving reproductive success independently of the recipients’ age. In donor cycles, recipients using oocytes from older donors had a statistically significantly lower LBR than younger donors. Currently, it still remains unclear whether the LBR differs between young donors versus old infertile patients in the context of euploid blastocyst transfers. Study design, size, duration Multicenter retrospective study with the preimplantation genetic test for aneuploidies (PGT-A) in both autologous and donor oocytes cycles between January 2018 and January 2021 was conducted at three different institutions (IVI-RMA, GeneraLife and Humanitas Fertility Center). 556 patients were included and matched 1:1 for the age of recipients, euploid blastocyst morphological quality, and day of development. In the frozen embryo transfers, endometrial preparation was done using hormonal replacement therapy (HRT) or natural cycles (NC). Participants/materials, setting, methods AMA patients older than 39 years underwent IVF. 556 patients who underwent autologous or donor oocyte cycles with at least one euploid blastocyst transferred were matched for oocyte age, blastocyst morphological quality and day of development. Blastocyst ploidy was assessed by aCGH or NGS analysis. Patients with uterine pathologies reported in the dataset were excluded. The primary outcome was LBR per first euploid blastocyst transfer. Outcomes were adjusted for confounders via logistic regression analyses. Main results and the role of chance 278 single euploid blastocysts tested by PGT-A were transferred in both autologous and donor oocyte cycles. No statistical differences were reported in the maternal age at transfer in the two groups (41.91 ± 2.03 and 41.75 ± 1.98, p = 0.55), endometrial thickness [(8.67, 95%CI: 8.45-8.88) and (8.36, 95%CI: 8.05-8.67)] and type of endometrial preparation (HRT or NC). Implantation rate and pregnancy rate were similar without statical difference in autologous or donor cycles, respectively [57.91%, (95%CI: 51.87-63.78) versus 56.83%, (95%CI: 50.79-62.74); p = 0.99)] and N = 158/278 (56.83%, 95%CI: 50.79-62.74) versus N = 161/278 (57.91%, 95%CI: 51.87-63.78), p = 0.86. The rate of ectopic pregnancy was not statistically different in both arms. Even the miscarriage rate was comparable in autologous N = 46/158, 16.55% (95%CI:12.38-21.45) versus donor group N = 45/161, 16.19%, (95%CI:12.06-21.05); p = 0.98. The LBR was not statistically different in autologous N = 111/278 (39.93%, 95%CI:34.13-45.95) and donor group 114/278 (41.01%, 95%CI:35.17-47.04), p = 0.86. No statistical difference was reported for gestational age and birthweight at delivery. The logistic regression analyzed as putative confounders: oocyte age, number of inseminated MII-oocytes, zygotes and euploid blastocysts, sperm parameters, endometrial preparation and endometrial thickness showed no statistical differences. Limitations, reasons for caution Despite the matched design, the retrospective nature is the major limitation of this study. Also, patients received PGT-A using NGS and CGH arrays technology. The aCGH analysis is less sensitive than more recent NGS technology. Lastly, the prevalence of adenomyosis could be underestimated due to retrospective data collection. Wider implications of the findings The dramatic decline in IVF treatment success is primarily caused by aneuploidies. Euploid blastocysts show LBR largely independent of oocyte age. Our study suggests no uterine effect of aging. The reproductive decline in women is mainly related to meiotic failure, therefore future insights should develop strategies to overcome chromosomal aneuploidies. Trial registration number NA

P-612 Comparison the effectiveness and safety of letrozole-stimulated and hormone replacement treatment in endometrial preparation for frozen embryo transfer in patients with polycystic ovary syndrome

Abstract Study question Whether letrozole-stimulated protocol has advantages over hormone replacement therapy (HRT) in frozen embryo transfer in patients with polycystic ovary syndrome (PCOS)? Summary answer Letrozole-stimulated protocol is more suitable for endometrial preparation than HRT in patients with PCOS, which can increase the live birth rate and reduce pregnancy complications. What is known already The current routine endometrial preparation protocol for women with PCOS is HRT. However, HRT is expensive, and recent studies have found HRT may increase the risk of adverse maternal and neonatal complications such as hypertensive disorders of pregnancy. Letrozole induces mono-ovulatory and has no antiestrogenic effect, and has been found to increase live birth rate compared with clomiphene in fresh embryo cycles. However, Letrozole is rarely used in frozen embryo cycles. Whether letrozole-stimulated protocol is suitable for frozen embryo transfer in patients with PCOS and for whom is suitable is still lack of evidence. Study design, size, duration This is a retrospective cohort study involving all frozen embryo transfer cycles with letrozole-stimulated and HRT for PCOS during the period from August 2018 to December 2020 at a tertiary care center. Participants/materials, setting, methods A total of 2011 letrozole-stimulated cycles and 2211 HRT cycles were included in the analysis. Multivariate Logistic regression was used to analyze the differences in clinical pregnancy rate, live birth rate, miscarriage rate, the incidence of other pregnancy and obstetric outcomes between letrozole-stimulated protocol and HRT after adjusting for possible confounding factors. Subgroup analysis was used to explore the population for which letrozole-stimulated protocol was suitable. Main results and the role of chance After adjusting for confounding, letrozole-stimulated protocol increased the clinical pregnancy rate (OR,1.44; 95%CI,1.21-1.70), live birth rate (OR,1.49; 95%CI,1.27-1.74) and reduced the incidence of miscarriage (OR, 0.71; 95%CI,0.55-0.92), hypertensive disorders of pregnancy (OR, 0.66; 95%CI,0.45,0.98), gestational diabetes mellitus (OR,0.75; 95%CI,0.57,0.98) and cesarean section (OR,0.78; 95%CI,0.61,0.99) than HRT. There were no significant differences in other outcomes such as preterm birth, small for gestational age, and large for gestational age between the two endometrial preparation protocols. Subgroup analysis according to maternal age, BMI, insulin resistance and PCOS classification showed that the live birth rate of letrozole-stimulated protocol was significantly higher than that of HRT in all subgroups. Limitations, reasons for caution This study is a retrospective study, the population characteristics of the two endometrial preparation protocols existed differences. Although multivariate logistic regression was used to adjust some factors, the interference of known and unknown factors on the outcomes cannot be completely avoided. Wider implications of the findings This retrospective study found letrozole-stimulated protocol has more advantages than HRT, which can improve the live birth rate and reduce the incidence of hypertensive disorders of pregnancy, gestational diabetes mellitus in patients with PCOS. High-quality well-powered randomised clinical trials and possible mechanistic studies are needed to further validate this conclusion. Trial registration number NA

P-109 Letrozole versus hormone replacement therapy for frozen embryo transfer: A randomized clinical trial

Abstract Study question Do the outcomes of frozen embryo transfer cycles differ according to endometrial preparation (EP) with letrozole versus hormone replacement therapy (HRT)? Summary answer Letrozole seems to be as effective as HRT preparation in frozen cycles in terms of treatment outcomes. What is known already Vitrification improved the survival of vitrified-warmed embryos and increased the number of FET cycles. A common EP strategy for FET includes augmentation of the endometrium using estrogen followed by progesterone supplements. Retrospective studies have shown that using aromatase inhibitors (letrozole) in FET cycles was associated with higher clinical pregnancy and live birth rates, with a lower miscarriage rate, as compared to HRT cycles. Letrozole maintains regular feedback mechanisms, facilitating normal follicular growth, and promotes single follicle development and ovulation. Moreover, it does not have any negative effects on the endometrium and can improve endometrial receptivity. Study design, size, duration This randomized controlled trial was performed in two university-affiliated medical centers. A total of 170 patients undergoing frozen embryo transfer cycles from June 2018 to June 2021 were eligible. Participants/materials, setting, methods Patients were randomized to either letrozole (n = 69) or HRT protocol (n = 101) for EP, using a blocked randomization method. Inclusion criteria were single blastocyst transfer with normal uterine cavity. Exclusion criteria were patients older than 40 years, oocyte donation cycles, or more than 3 previous transfers without a pregnancy. The primary study outcome was percentage of clinical pregnancies, defined as clinical pregnancies/embryo transfers, excluding canceled treatments. Main results and the role of chance The characteristics of the study groups were comparable in age, BMI, gravidity, parity, previous treatment history and characteristics of the relevant fresh cycle in which the embryo was frozen. After excluding 5 cancelled treatments in the letrozole group and 2 in the HRT group, the percentage of clinical pregnancies between the letrozole and HRT arms were similar (24 (38.0%) versus 34 (34.6%), respectively, p = 0.67). There was no difference in the percentages of live births (22 (34.9%) versus 28 (28.6%), respectively, p = 0.4) or missed abortions (1 (4.1%) versus 5 (14.7%), p = 0.19). For patients who did not achieve pregnancy in the randomized treatment cycle, we retrospectively examined the outcome of the next treatment cycle with the other EP protocol, when possible. Achievement of a clinical pregnancy was the same for change in treatment for both study groups (7(50%) in the letrozole group and 9(50%) in the HRT group). Limitations, reasons for caution Limitations of this study included the heterogeneous study groups. Even though class II ovulation disorders were similar in prevalence in both groups, they included different indications for ART. Pregnancy complications were not evaluated and should be further investigated in a study with a larger sample size. Wider implications of the findings Letrozole seems to be as effective as HRT for EP in frozen cycles, with possible advantages of fewer missed abortions and pregnancy complications. Letrozole could be a suitable option for EP, as it is effective and, enables more convenient timing, versus natural FET. Trial registration number NCT03540979

P-365 The composition of the endometrial microbiota, as determined by MicroBioMap®, significantly affects clinical outcomes in assisted reproduction treatments

Abstract Study question How does the presence of specific pathogenic or health-promoting microbial species in the endometrium relate to female fertility in assisted reproduction treatments (ART)? Summary answer Detection of endometrial pathogens using MicroBioMap® is associated with poor ART outcomes, whereas sterile endometria show the highest pregnancy and live birth rates. What is known already Vaginal eubiosis is characterised by low microbial diversity and dominance of Lactobacillus, which displays bioregulatory functions and prevents the growth of pathogenic microorganisms. Vaginal dysbiosis is directly linked to infertility and poor pregnancy outcomes. However, the endometrial microbiota composition and its role in fertility are more controversial. Robust reports show that chronic endometritis (CE) is highly prevalent among infertile patients, whose outcomes improve after antibiotic treatment. However, the role of Lactobacillus in this compartment, whether it also displays bioregulatory functions, or if it is essential and beneficial for women undergoing ART, is still unclear. Study design, size, duration This is a case-control retrospective study analysing the endometrial microbiota in the window of implantation (WOI) and the ART outcomes of 456 women undergoing IVF cycles in egg donation regimes with/without PGT-A (177 and 163 respectively), or using their own eggs in cycles with/without PGT-A (91 and 25 respectively), between March 2016 and April 2021 in IVF-Life Alicante (Spain). ART results after single embryo transfer (sET) of patients with different endometrial microbiota profiles were compared. Participants/materials, setting, methods Presence of 18 microbial CE pathogens and 4 Lactobacillus species was determined by high-throughput qPCR (MicroBioMap®) in 456 endometrial samples obtained during the WOI (determined by ER Map® receptivity test) of a hormone replacement therapy cycle. Clinical outcomes (clinical pregnancy, CP; live birth, LB) of sETs performed during the WOI (guided by ER Map®) were compared in relation to the endometrial microbiota profile. In PGT-A cycles, embryo ploidy was determined by NGS (VeriSeq-MiSeq) before sET. Main results and the role of chance According to the microbial profile detected by MicroBioMap®, patients were categorised as i) Lactobacillus only (L, n = 199), ii) Pathogens only (P, n = 56), iii) Lactobacillus + pathogens (L+P, n = 59) or iv) Undetected (U, n = 142). Absence of endometrial microorganisms was significantly associated to ART success. U-patients showed significantly higher CP (64.2% vs 50.8%, Fisheŕs exact p=0.046) and LB rates (52.9% vs 37.2%, p=0.03) after euploid sET than patients with microorganisms. These differences were more pronounced in patients receiving donor eggs (CP 70.2% vs 50.8%, p=0.026; LB 59.5% vs 40.2%, p=0.046). Presence of Lactobacillus in isolation in the endometrium showed a detrimental effect compared to U-environments. A trend towards statistical significance was detected, with L-patients showing lower LB rates compared to U-patients after euploid sET (38.8% vs 52.9%; p = 0.084). Detection of endometrial pathogens significantly reduced ART success rates. P-patients had significantly lower CP rates (64.2% vs 41.2%, p=0.038) after euploid sET than U-patients, and significantly lower CP (70.2% vs 36%, p=0.006) and LB rates (59.5% vs 21.7%, p=0.004) if receiving donor eggs. Interestingly, Lactobacillus dominance in pathogen-positive patients seemed to improve outcomes after euploid sET compared to pathogen-dominated patients (CP 56.7% vs 42.2%; LB 41.7% vs 31%). Limitations, reasons for caution This is a retrospective study. Randomised-control trials, non-selection studies and/or other investigations including antimicrobial treatments are needed to confirm these results and the extent of any clinical benefits. Endometrial biopsies were obtained transcervically. Although utmost care was taken, risk of contamination from the lower genital tract cannot be completely excluded. Wider implications of the findings Our results suggest that sterile endometria provide the best conditions for embryo implantation and pregnancy. Lactobacillus presence in endometrium might not be essential for pregnancy, and could even be detrimental if found in isolation. Presence of Lactobacillus as a bioregulator might only be beneficial if other pathogens co-colonise the tissue. Trial registration number Not applicable

The relationship between dominant follicle development and clinical outcomes of hormone replacement therapy-frozen embryo transfer: a retrospective clinical study.

Hormone replacement therapy (HRT) is one of the most used endometrial preparation protocols for frozen embryo transfer (FET) due to the convenience of its administration and stability of pregnancy outcomes. There are several HRT cycles accompanied by the development of dominant follicles. However, the relationship between dominant follicle development and clinical outcomes in HRT-FET cycles remains unclear. We carried out a retrospective cohort study of 13251 cycles at our reproductive medicine center from 2012 to 2019. Total cycles were divided into two groups according to whether there was dominant follicular development. In addition, we conducted a secondary analysis that used propensity-score matching to reduce confounding variables. A univariate and multivariable logistic regression model was further employed to analyze the effect of dominant follicle development in HRT cycles on clinical pregnancy outcomes. There was no significant correlation between dominant follicle development in HRT-FET cycles and the clinical pregnancy rate (adjusted OR = 1.162, 95% CI: 0.737-1.832, P = 0.52). In addition, there was a positive correlation between the basic follicle-stimulating hormone (FSH) level and the development of dominant follicles, while there was a negative correlation between antral follicle count (AFC), menstrual cycle length and the development of dominant follicles in HRT cycles. The development of dominant follicles in HRT-FET cycles does not affect the clinical pregnancy rate, early miscarriage rate and live birth rate. Therefore, it is not necessary to immediately cancel the FET cycle immediately when dominant follicle development is monitored in the HRT-FET cycle.

The future of frozen-thawed embryo transfer in hormone replacement therapy cycles.

This review focuses on the efficacy of letrozole stimulated frozen-thawed embryo transfer (FET) compared to hormone replacement therapy (HRT) FET in women with polycystic ovarian syndrome (PCOS) and/or oligo-anovulation. Further, obstetric and perinatal risks in HRT FET are summarized. The presence of a corpus luteum seems to reduce the risk of pregnancy-related hypertension and preeclampsia after FET. As a natural cycle (NC) FET is not an option for women with oligo-/amenorrhea these women may benefit from FET with mild stimulation compared to HRT FET. The intention of mild stimulation in anovulatory women is to induce (mono) ovulation to mimic the endocrine profiles of the natural cycle and the early pregnancy after natural conception. Mild stimulation by letrozole is patient friendly and cheap compared to gonadotropin stimulated FET and has been increasingly used in recent years. Although the quality of evidence is low, the pregnancy outcomes after letrozole FET seems similar or even better compared to HRT FET in women with PCOS and/or oligo-anovulation. Natural and modified NC FET should be used whenever possible to mitigate adverse obstetric and perinatal outcomes after HRT FET. For anovulatory women, whenever ovulation can be induced, we advocate the use of mild stimulation FET to create a corpus luteum awaiting results from RCTs limited to oligo-anovulatory women.