Higher live birth rate with stimulated rather than artificial cycle for frozen-thawed embryo transfer

What is the optimal means of preparing the endometrium in frozen-thawed embryo transfer cycles among anovulatory women? A retrospective cohort study

OBJECTIVE

Different endometrial preparation protocols are used prior to frozen-thawed embryo transfer (FET). It is not clear whether letrozole-stimulated cycles are beneficial for anovulatory women compared to artificial cycles (AC) in anovulatory women. Our objective was to investigate whether clinical outcomes following frozen-thawed embryo transfer in letrozole-stimulated cycles differ from artificial cycles in anovulatory women.

STUDY DESIGN

This is a retrospective cohort study conducted in a public fertility center in China comparing letrozole-stimulated and artificial cycles during FET. A total of 5,322 anovulatory women undergoing the first cycle of FET between January 2020 and December 2021. The primary outcome was the live birth rate. The secondary outcomes included biochemical pregnancy, clinical pregnancy, ongoing pregnancy, miscarriage, and ectopic pregnancy.

RESULTS

The live birth rates were significantly higher in the letrozole compared with AC (49.57 % vs. 45.22 %) both in the crude (odds ratio [OR] 1.19, 95 % confidence interval [CI] 1.01-1.40) and adjusted analysis (aOR 1.27, 95 %CI 1.08-1.50). After controlling for potential covariates, the adjusted probability of biochemical pregnancy (65.71 % vs. 63.25 %, aOR 1.20, 95 %CI: 1.01-1.43), clinical pregnancy (61.53 % vs. 58.79 %, aOR 1.20, 95 %CI: 1.02-1.43), and ongoing pregnancy (50.14 % vs. 45.66 %, aOR 1.28, 95 %CI: 1.08-1.51) were higher among those using letrozole-stimulated cycles than among those undergoing artificial cycles. The miscarriage rate was lower following letrozole compared with artificial cycles (aOR 0.59, 95 %CI: 0.43-0.80). The ectopic pregnancy in the letrozole group was similar to that in the artificial cycles.

CONCLUSIONS

Letrozole-stimulated FET was significantly associated with higher rates of biochemical pregnancy, clinical pregnancy, ongoing pregnancy and live birth, and with a lower rate of miscarriage, compared with artificial cycles.

Finding of the optimal preparation and timing of endometrium in frozen-thawed embryo transfer: a literature review of clinical evidence

Frozen-thawed embryo transfer (FET) has been a viable alternative to fresh embryo transfer in recent years because of the improvement in vitrification methods. Laboratory-based studies indicate that complex molecular and morphological changes in endometrium during the window of implantation after exogenous hormones with controlled ovarian stimulation may alter the interaction between the embryo and endometrium, leading to a decreased implantation potential. Based on the results obtained from randomized controlled studies, increased pregnancy rates and better perinatal outcomes have been reported following FET. Compared to fresh embryo transfer, fewer preterm deliveries, and reduced incidence of ovarian hyperstimulation syndrome were found after FETs, yet there is a trend of increased pregnancy-related hypertensive diseases in women receiving FET. Despite the increased application of FET, the search for the most optimal priming protocol for the endometrium is still undergoing. Three available FET protocols have been proposed to prepare the endometrium: i) natural cycle (true natural cycle and modified natural cycle) ii) artificial cycle (AC) or hormone replacement treatment cycle iii) mild ovarian stimulation (mild-OS) cycle. Emerging evidence suggests that the optimal timing for FET using warmed blastocyst transfer is the LH surge+6 day, hCG administration+7 day, and the progesterone administration+6 day in the true natural cycle, modified natural cycle, and AC protocol, respectively. Although still controversial, better clinical pregnancy rates and live birth rates have been reported using the natural cycle (true natural cycle/modified natural cycle) compared with the AC protocol. Additionally, a higher early pregnancy loss rate and an increased incidence of gestational hypertension have been found in FETs using the AC protocol because of the lack of a corpus luteum. Although the common clinical practice is to employ luteal phase support (LPS) in natural cycles and mild-OS cycles for FET, the requirement for LPS in these protocols remains equivocal. Recent findings obtained from RCTs do not support the routine application of endometrial receptivity testing to optimize the timing of FET. More RCTs with rigorous methodology are needed to compare different protocols to prime the endometrium for FET, focusing not only on live birth rate, but also on maternal, obstetrical, and neonatal outcomes.

Agonist long protocol improves outcomes of vitrified-warmed embryo transfer in repeatedly thin endometrium

RESEARCH QUESTION

Does follicular stimulation using human menopausal gonadotrophin (HMG) after pituitary down-regulation by a GnRH agonist improve endometrial thickness (EMT) and clinical outcomes of frozen-thawed embryo transfer (FET; using vitrified-warmed embryos) in women with thin endometrium after intensified oestrogen administration (IOA)?

DESIGN

This was a retrospective study. A total of 627 patients attempted 683 FET cycles with at least one previous history of thin endometrium. None of the cycles reached over 7 mm EMT after using oral and vaginal oestradiol for more than 21 days (IOA protocol). A total of 129 cycles proceeded with FET, 305 cycles were cancelled, and 249 cycles involved administration of HMG following GnRH agonist pituitary down-regulation (GnRH agonist + HMG protocol) for further endometrial preparation.

RESULTS

EMT became significantly greater (7.18 ± 1.14 mm versus 6.13 ± 0.63 mm, P < 0.001) using GnRH agonist + HMG compared with previous IOA cycles, but this was not related to serum oestrogen concentrations. A total of 213 cycles after the GnRH agonist + HMG protocol proceeded with FET, showing a significantly increased clinical pregnancy rate, implantation rate and live birth rate compared with those after IOA.

CONCLUSIONS

The GnRH agonist + HMG protocol for endometrial preparation in FET cycles improves EMT in women with a thin endometrium after IOA and showed significantly better clinical outcomes than IOA. The authors suggest that the GnRH agonist + HMG protocol should be used for EMT that is less than 7 mm after there has been no optimal response to IOA.

The effect of mildly stimulated cycle versus artificial cycle on pregnancy outcomes in overweight/obese women with PCOS prior to frozen embryo transfer: a retrospective cohort study

Background

Previous studies have shown that frozen embryo transfer (FET) resulted in increased live birth rates (LBR) and reduced the risk of ovarian hyperstimulation syndrome (OHSS) than did fresh embryo transfer in women with polycystic ovary syndrome (PCOS). In addition, overweight/obese women with PCOS are at increased risk of subfertility and complications of pregnancy, compared with normal-weight women. The ovarian stimulation and artificial hormone regimes are the two more commonly used endometrial preparation protocols in PCOS patients.This retrospective study aims to compare the pregnancy outcomes of mildly stimulated cycles (mSTC) and artificial cycles (AC) prior to FET in overweight/obese women with PCOS.

Methods

A retrospective analysis was conducted in overweight/obese women with PCOS who underwent their first FET cycles from January 2018 to December 2020. Two endometrial preparation protocols were used: the mildly stimulated cycles (N = 173) and the artificial cycles (N = 507). All pregnancy outcomes were analyzed by Student’s t-test, Chi-square (χ²) statistics and multivariable logistic regression analyses.

Results

This study enrolled 680 cases of FET cycles. The mSTC group exhibited significantly higher LBR compared with the AC group (49.7% vs. 41.0%; P = 0.046), while the rate of miscarriage was significantly lower (6.4% vs. 23.0%; P < 0.001). No statistically significant differences were observed in positive pregnancy rate (57.8% vs. 60.0%, P = 0.618), clinical pregnancy rate (54.3% vs. 55.6%, P = 0.769), and ectopic pregnancy rate (2.1% vs. 3.2%, P = 0.860) between two groups. After adjusting for possible confounding factors, multivariate logistic regression analysis also yielded similar results.

Conclusions

For overweight/obese women with PCOS, mSTC-FET demonstrated a higher LBR and a lower pregnancy loss rate than that in the AC-FET. When considering the most cost-effective treatment with the least adverse effects on patients, the mSTC for FET endometrial preparation may be considered. To corroborate our findings, additional prospective randomized clinical trials with larger sample sizes are required.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04728-6.

Comparison of two endometrial preparation methods for frozen-thawed embryo transfer in anovulatory PCOS patients: impact on miscarriage rate

OBJECTIVE

- Some studies have suggested that patients with polycystic ovary syndrome (PCOS) are at high risk of miscarriage. However, this still remains controversial. Several potential factors might explain this association: obesity, hyperinsulinemia and hyperandrogenism. Artificial and stimulated cycles appear to be comparable for endometrial preparation in frozen-thawed embryo transfer (FET) in PCOS patients. Only a few studies have assessed miscarriage rates specifically in PCOS. We have evaluated the impact of endometrial preparation on FET outcomes in anovulatory PCOS patients.

METHODS

- A retrospective cohort study was conducted at the Lille University Hospital, including 255 FET cycles in 134 PCOS patients between January 2011 and December 2017. PCOS was defined by the presence of at least two of the three Rotterdam's criteria. Patients were under 35 years old. Two endometrial preparation protocol were studied: stimulated cycle (gonadotropins on the second day of the cycle and luteal phase support including natural progesterone 600 mg/day) and artificial cycle (6 mg oral estradiol valerate and 800 mg micronized vaginal progesterone daily).

RESULTS

- 137 FET were performed under stimulated cycle and 118 FET under artificial cycle. Early pregnancy rates (30% versus 37.3%, p = NS), miscarriage rates (22% versus 25%, p = NS) and live birth rates (23.4% versus 26.3%, p = NS) were similar.

CONCLUSIONS

- In anovulatory PCOS women, the type of endometrial preparation does not influence FET outcomes, specifically regarding the miscarriage rate.

Impact of endometrial preparation on early pregnancy loss and live birth rate after frozen embryo transfer: a large multicenter cohort study (14,421 frozen cycles)

STUDY QUESTION

Does the endometrial preparation protocol (artificial cycle (AC) vs natural cycle (NC) vs stimulated cycle (SC)) impact the risk of early pregnancy loss and live birth rate after frozen/thawed embryo transfer (FET)?

SUMMARY ANSWER

In FET, ACs were significantly associated with a higher pregnancy loss rate and a lower live birth rate compared with SC or NC.

WHAT IS KNOWN ALREADY

To date, there is no consensus on the optimal endometrial preparation in terms of outcomes. Although some studies have reported a higher pregnancy loss rate using AC compared with NC or SC, no significant difference was found concerning the pregnancy rate or live birth rate. Furthermore, no study has compared the three protocols in a large population.

STUDY DESIGN, SIZE, DURATION

A multicenter retrospective cohort study was conducted in nine reproductive health units in France using the same software to record medical files between 1 January 2012 and 31 December 2016. FET using endometrial preparation by AC, modified NC or SC were included. The primary outcome was the pregnancy loss rate at 10 weeks of gestation. The sample size required was calculated to detect an increase of 5% in the pregnancy loss rate (21–26%), with an alpha risk of 0.5 and a power of 0.8. We calculated that 1126 pregnancies were needed in each group, i.e. 3378 in total.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were collected by automatic extraction using the same protocol. All consecutive autologous FET cycles were included: 14 421 cycles (AC: n = 8139; NC: n = 3126; SC: n = 3156) corresponding to 3844 pregnancies (hCG > 100 IU/l) (AC: n = 2214; NC: n = 812; SC: n = 818). Each center completed an online questionnaire describing its routine practice for FET, particularly the reason for choosing one protocol over another.

MAIN RESULTS AND THE ROLE OF CHANCE

AC represented 56.5% of FET cycles. Mean age of women was 33.5 (SD ± 4.3) years. The mean number of embryos transferred was 1.5 (±0.5). Groups were comparable, except for history of ovulation disorders (P = 0.01) and prior delivery (P = 0.03), which were significantly higher with AC. Overall, the early pregnancy loss rate was 31.5% (AC: 36.5%; NC: 25.6%; SC: 23.6%). Univariable analysis showed a significant association between early pregnancy loss rate and age >38 years, history of early pregnancy loss, ovulation disorders and duration of cryopreservation >6 months. After adjustment (multivariable regression), the early pregnancy loss rate remained significantly higher in AC vs NC (odds ratio (OR) 1.63 (95% CI) [1.35–1.97]; P < 0.0001) and in AC vs SC (OR 1.87 [1.55–2.26]; P < 0.0001). The biochemical pregnancy rate (hCG > 10 and lower than 100 IU/l) was comparable between the three protocols: 10.7% per transfer.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by its retrospective design that generates missing data. Routine practice within centers was heterogeneous. However, luteal phase support and timing of embryo transfer were similar in AC. Univariable analysis showed no difference between centers. Moreover, a large number of parameters were included in the analysis.

WIDER IMPLICATIONS OF THE FINDINGS

Our study shows a significant increase in early pregnancy loss when using AC for endometrial preparation before FET. These results suggest either a larger use of NC or SC, or an improvement of AC by individualizing hormone replacement therapy for patients in order to avoid an excess of pregnancy losses.

STUDY FUNDING/COMPETING INTEREST(S)

The authors declare no conflicts of interest in relation to this work. G.P.-B. declares consulting fees from Ferring, Gedeon-Richter, Merck KGaA, Theramex, Teva; Speaker’s fees or equivalent from Merck KGaA, Ferring, Gedeon-Richter, Theramex, Teva. N.C. declares consulting fees from Ferring, Merck KGaA, Theramex, Teva; Speaker’s fees or equivalent from Merck KGaA, Ferring. C.R. declares a research grant from Ferring, Gedeon-Richter; consulting fees from Gedeon-Richter, Merck KGaA; Speaker’s fees or equivalent from Merck KGaA, Ferring, Gedeon-Richter; E.M.d’A. declares Speaker’s fees or equivalent from Merck KGaA, MSD, Ferring, Gedeon-Richter, Theramex, Teva. I.C-D. declares Speaker’s fees or equivalent from Merck KGaA, MSD, Ferring, Gedeon-Richter, IBSA. N.M. declares a research grant from Merck KGaA, MSD, IBSA; consulting fees from MSD, Ferring, Gedeon-Richter, Merck KGaA; Speaker’s fees or equivalent from Merck KGaA, MSD, Ferring, Gedeon-Richter, Teva, Goodlife, General Electrics.

TRIAL REGISTRATION NUMBER

N/A.

Luteal phase support for natural cycle frozen embryo transfer: a meta-analysis

PURPOSE

We aimed to evaluate the effect of luteal phase support (LPS) on pregnancy outcome in natural cycle frozen embryo transfer (NC-FET).

METHOD

We searched PubMed, Cochrane Library, Embase for related literature from start to February 2020. Relative risk ratio (RR) and 95% confidence intervals (95% CI) in random-effects, fixed-effects models were calculated using Review Manager 5.3.

RESULTS

Totally 9 studies were included in the meta-analysis. The results showed no significant difference could be found regarding chemical pregnancy rate (RR 1.07, 95% CI 0.93-1.22; I² = 54%) and miscarriage rate (RR 0.92, 95% CI 0.70-1.22; I² = 0%) between the LPS groups and no LPS groups in NC-FET. LPS groups has increased the rate of clinical pregnancy rate (RR 1.23, 95% CI 1.12-1.34; I² = 52%) compared with no LPS groups. Subgroup analysis according to trigger administration also showed a significant difference between the two groups.

CONCLUSION

LPS might improve the clinical pregnancy rate in NC-FET. HCG trigger for ovulating may result in luteal phase deficiency. LPS subsequently improved clinical pregnancy rate and chemical pregnancy rate for patients undergoing HCG trigger and NC-FET.

RETROSPECTIVELY REGISTERED

This meta-analysis was registered at PROSPERO, PROSPERO ID is CRD42020171758.

Pregnancy Outcomes After Frozen-Thawed Embryo Transfer in the Absence of a Corpus Luteum

Background: Nowadays, frozen-thawed embryo transfer (FET) cycles represent a high proportion of fertility treatments worldwide. Recent studies suggest differences in pregnancy outcomes depending on the FET treatment protocol used. The reason for this is still unclear, but the number of corpora lutea (CL) at conception is discussed as a possible factor. This study aims to investigate whether maternal and neonatal outcomes for pregnancies following FET lacking a CL differ from FET with one or more CL in order to explore a potential link between CL absence and adverse pregnancy outcomes.

Methods: The study was designed as a retrospective, multi-center observational study with two cohorts after singleton live birth [0 CL cohort (FET in a programmed cycle, n = 114) and ≥ 1 CL cohort (FET in a natural or stimulated cycle, n = 68)]. Participants completed a questionnaire on the outcome of pregnancy and birth records were analyzed in a descriptive way. Multivariable logistic and linear regressions were performed in order to explore associations between CL absence and pregnancy outcomes. The strength of the agreement between the information in the survey and the diagnoses extracted from the files was assessed by Cohen's Kappa.

Results: The risk of hypertensive disorders of pregnancy was higher after FET in the absence of a CL compared to FET with CL presence (aOR 5.56, 95% CI 1.12 – 27.72). Birthweights and birthweight percentiles were significantly higher in the 0 CL group. CL absence was a predictor of higher birthweight (adjusted coefficient B 179.74, 95% CI 13.03 – 346.44) and higher birthweight percentiles (adjusted coefficient B 10.23, 95%, 95% CI 2.28 – 18.40) particularly in female newborns of the 0 CL cohort. While the strength of the agreement between the reported information in the survey and the actual diagnoses extracted from the files was good for the majority of outcomes of interest it was fair in terms of hypertension (κ = 0.38).

Conclusion: This study supports observations suggesting a potential link between a lack of CL at conception and adverse maternal and neonatal outcomes. Further investigations on causes and pathophysiological relationships are yet to be conducted.

Long-term pituitary downregulation before frozen embryo transfer improves clinical outcomes in women positive for serum autoantibodies

OBJECTIVE

Autoantibodies are associated with worse outcomes in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI), including increasing miscarriage rate, lowering pregnancy rate, and lowering delivery rate. However, little is known about improving IVF/ICSI outcomes for autoantibody-positive women, especially in frozen-thawed embryo transfer (FET) cycles. This study aimed to investigate whether pituitary suppression before FET improves the clinical pregnancy rate (CPR) and live birth rate (LBR) for IVF/ICSI women positive for serum autoantibodies.

STUDY DESIGN

A total of 181 infertile women positive for serum autoantibodies were recruited, including 65 women receiving GnRHa and hormone replacement therapy protocols (G-HRT group) and 116 women using modified natural cycles (MNC)/mild stimulated cycles (MSC) as FET protocols (MNC/MSC group). The outcomes were compared between two groups, including CPR, implantation rate (IR), miscarriage rate (MR), ongoing pregnancy rate (OPR), LBR, and gestational age (GA). The primary outcome of the study was CPR.

RESULTS

CPR, OPR, and LBR per embryo transferred in the G-HRT groups were significantly higher than those in the MNC/MSC group. No statistically significant differences were observed in the IR and MR. The CPR, IR, MR, OPR, and LBR was 72.23%, 64.00%, 12.77%, 63.07%, and 63.07% in the G-HRT group, respectively, while that was 56.90%, 53.07%, 10.60%, 50.00%, and 50.00% in the MNC/MSC group, respectively. After adjusting for partial potential confounding factors using multiple logistic regression, the type of endometrial preparation is the factor independently associated with enhanced CPR (OR = 0.48, 95%CI: 0.24-0.96, P = 0.039).

CONCLUSIONS

The current study showed that prior long-term GnRHa suppression could benefit patients with high serum autoantibody levels during IVF/ICSI FET cycles.

Preparation of the Endometrium for Frozen Embryo Transfer: A Systematic Review

Despite the worldwide increase in frozen embryo transfer, the search for the best protocol to prime endometrium continues. Well-designed trials comparing various frozen embryo transfer protocols in terms of live birth rates, maternal, obstetric and neonatal outcome are urgently required. Currently, low-quality evidence indicates that, natural cycle, either true natural cycle or modified natural cycle, is superior to hormone replacement treatment protocol. Regarding warmed blastocyst transfer and frozen embryo transfer timing, the evidence suggests the 6th day of progesterone start, LH surge+6 day and hCG+7 day in hormone replacement treatment, true natural cycle and modified natural cycle protocols, respectively. Time corrections, due to inter-personal differences in the window of implantation or day of vitrification (day 5 or 6), should be explored further. Recently available evidence clearly indicates that, in hormone replacement treatment and natural cycles, there might be marked inter-personal variation in serum progesterone levels with an impact on reproductive outcomes, despite the use of the same dose and route of progesterone administration. The place of progesterone rescue protocols in patients with low serum progesterone levels one day prior to warmed blastocyst transfer in hormone replacement treatment and natural cycles is likely to be intensively explored in near future.

Comparison of Stimulated Cycles with Low Dose r-FSH versus Hormone Replacement Cycles for Endometrial Preparation Prior to Frozen-Thawed Embryo Transfer in Young Women with Polycystic Ovarian Syndrome: A Single-Center Retrospective Cohort Study from China

Objective

The principal purpose of this study was to compare reproductive outcomes for stimulated cycles (STC) and hormone replacement cycles (HRC) for endometrial preparation before frozen-thawed embryo transfer (FET) in young women with polycystic ovary syndrome (PCOS).

Methods

We conducted a retrospective study of 1434 FET cycles from January, 2017 to March, 2020 in our reproductive center, in which stimulated and hormone replacement cycles were used for endometrial preparation. Pregnancy outcomes of couples undergoing routine STC-FET or HRC-FET were analyzed by propensity score matching (PSM) and multivariable logistic regression analyses.

Results

Data on 1234 HRC protocols (86% of the total) and 200 STC protocols (14%) were collected. After PSM, 199 patients were included in both groups, respectively. There was no significant difference in positive pregnancy rate (52.7% vs 54.8%, p=0.763), clinical pregnancy rate (51.8% vs 52.8%, p=0.841), live birth rate (45.2% vs 43.7%, p=0.762), pregnancy loss rate (9.7% vs 16.2%, p=0.164) and ectopic pregnancy rate (1.5% vs 0.5%, p=0.615) between STC and HRC protocols. Subsequent multivariate logistic regression analysis also yielded similar results.

Conclusion

STC for endometrial preparation had similar pregnancy outcomes compared with HRC protocols. Evidence is available which shows that for young women with PCOS in preparation for FET, HRC could be a reasonable choice for patients who are unwilling to accept injections. However, STC may reduce unnecessary anxiety and operational costs and offer more flexibility for patients. Eventually, we must embrace the concepts of individualization, securitization, and optimization in the clinic.

Stimulated cycle versus artificial cycle for frozen embryo transfer in patients with polycystic ovary syndrome: a Meta-analysis

PURPOSE

Our aim is to conduct a meta-analysis comparing clinical outcomes between the mild ovarian stimulation cycle versus an artificial cycle (AC) for frozen embryo transfer (FET) in patients with polycystic ovary syndrome (PCOS).

METHODS

We systematically searched the databases of PubMed, EMBASE and the Cochrane Library from inception to January 2020. The outcomes were live birth rate (LBR), ongoing pregnancy rate (OPR), clinical pregnancy rate (CPR), embryo implantation rate (IR) and miscarriage rate (MR). The mild ovarian stimulation cycle and AC were compared according to risk ratios and 95% confidence intervals using a fixed or random effects model.

RESULTS

Four retrospective studies describing the clinical outcomes were included. We found no significant difference in LBR, OPR, CPR, IR or MR between the mild ovarian stimulation cycle and AC protocols, whereas a lower MR was found for the letrozole-stimulated cycle than the AC.

CONCLUSIONS

The letrozole-stimulated cycle for endometrial preparation in PCOS patients undergoing FET may lower the MR more than the AC. PCOS patients using the mild ovarian stimulation cycle for endometrial preparation undergoing FET had similar LBR, OPR, CPR and IR compared with the AC. The letrozole-stimulated protocol may be a reasonable choice for endometrial preparation before FET for women with PCOS.

Ovulatory-Based FET Cycles May Achieve Higher Pregnancy Rates in the General Population and among Anovulatory Women

This study evaluated which endometrial preparation protocol in frozen embryo transfer (FET) cycles provides the best results for polycystic ovarian syndrome (PCOS) patients and the general population. This retrospective study of 634 FET cycles was conducted 2016-2018. Cycles were divided into Group A: Artificial endometrial preparations for FET (aFET; n = 348), Group B: Ovulatory cycle (n = 286) to compare two methods of endometrial preparation for FET. Artificial endometrial preparation with exogenous estrogen and progesterone versus natural ovulation cycles, modified natural cycles using hCG for the final triggering and letrozole-induced ovulation with hCG. Anovulatory patients were analyzed separately. Anovulatory PCOS patients had significantly higher pregnancy rates with letrozole treatment compared with aFET cycles (44% vs. 22.5%; p = 0.044). For the entire cohort, ovulatory cycles and aFET were similar in terms of patient characteristics, demographics, infertility causes, treatment protocols and number of embryos transferred. Although the mean ESHRE score of the transferred embryos was higher in the aFET group, we found higher clinical pregnancy rate in the ovulatory cycle FET (41.3% vs. 27.3%, p < 0.0001). A better pregnancy rate was found after ovulatory cycle FET. In the ovulatory cycles, the outcome of letrozole-induced and non-induced cycles were comparable. PCOS patients, as well as the general population, may benefit from ovulation induced FET cycles, with significantly better outcomes in FET in ovulatory cycles.

The effect of letrozole versus artificial hormonal endometrial preparation on pregnancy outcome after frozen-thawed embryos transfer cycles: a randomized clinical trial

BACKGROUND

Considering that clinical trial studies are limited in polycystic ovary syndrome (PCOS) patients, and there is no consensus on an optimum endometrial preparation protocol for frozen embryo transfer (FET), the present study was designed as a randomized clinical trial to compare the reproductive outcomes following stimulated cycles with letrozole plus human menopausal gonadotropin (HMG) for endometrial preparation compared with routine AC-FET.

METHODS

This randomized controlled trial was carried out on infertile PCOS patients who underwent IVF/ICSI and FET cycles in Arash Women's Hospital affiliated to Tehran University of Medical Sciences between September 2018 and January 2020. PCOS diagnosis was based on the Rotterdam criteria. Eligible patients were randomly allocated into two groups: stimulated cycle with letrozole plus (HMG) (intervention group) and routine artificial hormonal endometrial preparation (control group).

RESULTS

One hundred seventy-seven infertile patients were recruited for participation in the study. Of these, 57 women were excluded due to non-eligibility for entering the study, and a total of 120 patients were randomly assigned to two study groups. After follow up, the cycle outcomes of 57 patients in the intervention group and 59 patients in the control group were compared. The data analysis showed that the two groups did not have significant differences in fundamental and demographic characteristics. After the intervention, there were no significant differences in implantation rate, chemical, ectopic, and clinical pregnancy rates between groups. Moreover, the rates of miscarriage and ongoing pregnancy were similar between groups (P > 0.05).

CONCLUSIONS

We found similar pregnancy outcomes with two endometrial preparation methods. Noting that each treatment centre should select the most beneficial and cost-effective method with the least adverse effects for patients, letrozole preparations for FET could be incorporated into possible options; however, establishing this approach as first-line treatment is premature in light of current evidence, and future randomized clinical trials with larger sample sizes are required for widespread application.

TRIAL REGISTRATION

The study was also registered in the Iranian Registry of Clinical Trials on March 20th, 2020. ( IRCT20090526001952N12 at www.irct.ir , registered retrospectively).

Serum progesterone level and ongoing pregnancy rate following frozen-thawed embryo transfer after artificial endometrial preparation: a monocentric retrospective study

INTRODUCTION

In some studies, early pregnancy loss (EPL) rate is higher with artificial cycle (AC) endometrial preparation for frozen-thawed embryo (FET) transfer than with other protocols, even though pregnancy rates are similar. An inadequate luteal phase support could explain these findings. The aim of this study was to compare, among the patients who had a pregnancy after FET with AC endometrial preparation, serum progesterone (PG) levels between those who experienced an EPL or an ongoing pregnancy.

MATERIAL AND METHODS

A monocentric retrospective cohort study, conducted at a University affiliated fertility center, studied 130 FET cycles with AC endometrial preparation between June 2016 and July 2017. Serum PG rates were compared according to reproductive outcomes and to endometrial preparation protocol on day 10 or 12 after FET (PG0) according to the embryo stage, and every 48h in case of pregnancy (i.e. PG1; PG2).

RESULTS

Among patients who had a pregnancy after FET with AC (n=33), serum PG levels were higher in case of an ongoing pregnancy than EPL, only significantly at PG1 (PG0 12.4ng/mL [7.5-14.6] vs 8.2ng/mL [6.0-13.0], p= 0.320; PG1 15.0 ng/mL [14.0-15.9] vs 8.5ng/mL [5.9-13.8], p= 0.048).

DISCUSSION

We found that serum PG level was lower in women experiencing early pregnancy loss after FET with AC endometrial preparation, potentially reflecting a lack of appropriate luteal phase support with PG. A cycle AC test, monitoring serum PG levels after its steady state, could detect this lack of PG, allowing physicians to adapt PG supplementation.

Live birth after frozen-thawed embryo transfer: which endometrial preparation protocol is better?

OBJECTIVE

To compare the clinical outcomes of modified natural cycle (mNC) and artificial cycle (AC) protocols for frozen embryo transfers.

MATERIAL AND METHODS

A total of 490 frozen-thawed autologous embryo transfer cycles, performed in a single tertiary IVF center, between January 2015 and September 2017, were retrospectively analyzed. Of these, 214 cycles were performed after mNC and 276 cycles were performed after gonadotrophin-releasing hormone (GnRH) agonist plus sequential estrogen and progestin priming protocol. The primary outcome was live birth and secondary outcomes were clinical pregnancy, implantation and miscarriage rates. Multivariate regression analysis was used to adjust covariates on clinical outcome.

RESULTS

The rates of live birth (33.6 % vs. 29.3 %, respectively), clinical pregnancy (40.2 % vs. 36.6 %, respectively), implantation (32.3 % vs. 28.5 %, respectively), and miscarriage (5.1 % vs. 6.9 %, respectively) were not different between the mNC and AC groups. Multivariate analysis also showed that the method for endometrial preparation had no significant effect on clinical pregnancy and live birth. The adjusted odds ratios (OR) of live births and clinical pregnancies were 0.97 (95 % CI 0.64-1.48) and 0.98 (95 % CI 0.65-1.46) for the AC compared to mNC group. However, there was a significant difference between mNC and AC in cycles in which double embryo transfer was performed. The live birth (48 % vs. 31.4 %P= 0.01) and clinical pregnancy rates (53.9 % vs. 38.8 %, P= 0.02) were significantly higher in the mNC group than the AC group for double embryo transfers.

CONCLUSION

The live birth and clinical pregnancy rates are comparable between mNC and AC with GnRH agonists in frozen thawed embryo transfer cycles. In ovulatory patients with planned double embryo transfer, mNC can be considered. Further well-designed prospective studies are needed to confirm our results.