GnRH agonist versus GnRH antagonist in oocyte donation cycles: a prospective randomized study

A modified flexible GnRH antagonist protocol using antagonist early cessation and a gonadotropin step-down approach improves live birth rates in fresh cycles: a randomized controlled trial

STUDY QUESTION

Can pregnancy outcomes following fresh elective single embryo transfer (eSET) in gonadotropin-releasing hormone (GnRH) antagonist protocols increase using a gonadotropin (Gn) step-down approach with cessation of GnRH antagonist on the day of hCG administration (hCG day) in patients with normal ovarian response?

SUMMARY ANSWER

The modified GnRH antagonist protocol using the Gn step-down approach and cessation of GnRH antagonist on the hCG day is effective in improving live birth rates (LBRs) per fresh eSET cycle.

WHAT IS KNOWN ALREADY

Currently, there is no consensus on optimal GnRH antagonist regimens. Studies have shown that fresh GnRH antagonist cycles result in poorer pregnancy outcomes than the long GnRH agonist (GnRHa) protocol. Endometrial receptivity is a key factor that contributes to this phenomenon.

STUDY DESIGN, SIZE, DURATION

An open label randomized controlled trial (RCT) was performed between November 2021 and August 2022. There were 546 patients allocated to either the modified GnRH antagonist or the conventional antagonist protocol at a 1:1 ratio.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Both IVF and ICSI cycles were included, and the sperm samples used were either fresh or frozen from the partner, or from frozen donor ejaculates. The primary outcome was the LBRs per fresh SET cycle. Secondary outcomes included rates of implantation, clinical and ongoing pregnancy, miscarriage, and ovarian hyperstimulation syndrome (OHSS), as well as clinical outcomes of ovarian stimulation.

MAIN RESULTS AND THE ROLE OF CHANCE

Baseline demographic features were not significantly different between the two ovarian stimulation groups. However, in the intention-to-treat (ITT) population, the LBRs in the modified antagonist group were significantly higher than in the conventional group (38.1% [104/273] vs. 27.5% [75/273], relative risk 1.39 [95% CI, 1.09-1.77], P = 0.008). Using a per-protocol (PP) analysis which included all the patients who received an embryo transfer, the LBRs in the modified antagonist group were also significantly higher than in the conventional group (48.6% [103/212] vs. 36.8% [74/201], relative risk 1.32 [95% CI, 1.05-1.66], P = 0.016). The modified antagonist group achieved significantly higher implantation rates, and clinical and ongoing pregnancy rates than the conventional group in both the ITT and PP analyses (P < 0.05). The two groups did not show significant differences between the number of oocytes retrieved or mature oocytes, two-pronuclear zygote (2PN) rates, the number of embryos obtained, blastocyst progression and good-quality embryo rates, early miscarriage rates, or OHSS incidence rates (P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

A limitation of our study was that the subjects were not blinded to the treatment allocation in the RCT trial. Only women under 40 years of age who had a good prognosis were included in the analysis. Therefore, use of the modified antagonist protocol in older patients with a low ovarian reserve remains to be investigated. In addition, the sample size for Day 5 elective SET was small, so larger trials will be required to strengthen these findings.

WIDER IMPLICATIONS OF THE FINDINGS

The modified GnRH antagonist protocol using the Gn step-down approach and cessation of GnRH antagonist on hCG day improved the LBRs per fresh eSET cycle in normal responders.

STUDY FUNDING/COMPETING INTEREST(S)

This project was funded by grant 2022YFC2702503 from the National Key Research & Development Program of China and grant 2021140 from the Beijing Health Promotion Association. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

The RCT was registered in the Chinese Clinical Trial Registry; Study Number: ChiCTR2100053453.

TRIAL REGISTRATION DATE

21 November 2021.

DATE OF FIRST PATIENT’S ENROLLMENT

23 November 2021.

Ovarian stimulation for oocyte donation: a systematic review and meta-analysis

BACKGROUND

Since its introduction in the 1980s, oocyte donation (OD) has been largely integrated into ART. Lately, both demand and the indications for OD have increased greatly. Oocyte donors are healthy and potentially fertile women undergoing voluntarily ovarian stimulation (OS). Selection of the optimal type of stimulation is of paramount importance in order to achieve the most favourable outcomes for the oocyte recipients, but most importantly for the safety of the oocyte donors.

OBJECTIVE AND RATIONALE

This is the first systematic review (SR) with the objective to summarize the current evidence on OS in oocyte donors. The scope of this SR was to evaluate the OD programme by assessing four different aspects: how to assess the ovarian response prior to stimulation; how to plan the OS (gonadotrophins; LH suppression; ovulation trigger; when to start OS); how to control for the risk of ovarian hyperstimulation syndrome (OHSS) and other complications; and the differences between the use of fresh versus vitrified donated oocytes.

SEARCH METHODS

A systematic literature search was conducted in May 2020, according to PRISMA guidelines in the databases PubMed and Embase, using a string that combined synonyms for oocytes, donation, banking, freezing, complications and reproductive outcomes. Studies reporting on the safety and/or efficacy of OS in oocyte donors were identified. The quality of the included studies was assessed using ROBINS-I and ROB2. Meta-analysis was performed where appropriate. Data were combined to calculate mean differences (MD) for continuous variables and odd ratios (OR) for binary data with their corresponding 95% CIs. Heterogeneity between the included studies was assessed using I2 and tau statistics.

OUTCOMES

In total, 57 manuscripts were selected for the review, out of 191 citations identified. Antral follicle count and anti-Müllerian hormone levels correlate with ovarian response to OS in OD but have limited value to discriminate donors who are likely to show either impaired or excessive response. Five randomized controlled trials compared different type of gonadotrophins as part of OS in oocyte donors; owing to high heterogeneity, meta-analysis was precluded. When comparing different types of LH control, namely GnRH antagonist versus agonist, the studies showed no differences in ovarian response. Use of progesterone primed ovarian stimulation protocols has been evaluated in seven studies: the evidence has shown little or no difference, compared to GnRH antagonist protocols, in mean number of retrieved oocytes (MD 0.23, [95% CI 0.58-1.05], n = 2147; 6 studies; I2 = 13%, P = 0.33) and in clinical pregnancy rates among recipients (OR 0.87 [95% CI 0.60-1.26], n = 2260, I2 = 72%, P < 0.01). There is insufficient evidence on long-term safety for babies born. GnRH agonist triggering is the gold standard and should be used in all oocyte donors, given the excellent oocyte retrieval rates, the practical elimination of OHSS and no differences in pregnancy rates in recipients (four studies, OR 0.86, 95%CI 0.58-1.26; I2 = 0%). OS in OD is a safe procedure with a low rate of hospitalization after oocyte retrieval. The use of a levonorgestrel intrauterine device or a progestin contraceptive pill during OS does not impact the number of oocytes retrieved or the clinical pregnancy rate in recipients. Ultrasound monitoring seems enough for an adequate follow up of the stimulation cycle in OD. Use of fresh versus vitrified donated oocytes yielded similar pregnancy outcomes.

WIDER IMPLICATIONS

This update will be helpful in the clinical management of OS in OD based on the most recent knowledge and recommendations, and possibly in the management of women under 35 years undergoing oocyte vitrification for social freezing, owing to the population similarities. More clinical research is needed on OS protocols that are specifically designed for OD, especially in term of the long-term safety for newborns, effective contraception during OS, and treatment satisfaction.

Suboptimal endometrial-embryonal synchronization is a risk factor for ectopic pregnancy in assisted reproduction techniques

RESEARCH QUESTION

What are the main risk factors associated with ectopic pregnancy and what is the true incidence of ectopic pregnancies in an IVF programme?

DESIGN

Retrospective single-centre study of 12,429 blastocyst transfers (8182 fresh and 4247 frozen embryo transfers) conducted between January 2010 and December 2017. IVF outcome was analysed, and ectopic pregnancy risk evaluated according to patient's characteristics and assisted reproductive technology treatment factors.

RESULTS

Of 5061 patients reporting a positive pregnancy test, 43 were diagnosed with ectopic pregnancy (0.85%). Neither female age (36.7 versus 35.8 years), body mass index, quality of transfer nor stimulation protocol affected the ectopic pregnancy rate, but history of previous ectopic pregnancy (OR 3.26; P = 0.0080), tubal surgery, or both (OR 6.20; P < 0.0001) did. The incidence of ectopic pregnancy was increased in women with uterine malformations (OR 3.85; P = 0.0052), uterine pathologies (OR 5.35; P = 0.0001), uterine surgeries (OR 2.29; P = 0.0154) or sub-optimal endometrial build-up (OR 4.46 to 5.31; P < 0.0001). Transfer of slow-developing blastocysts (expressed by expansion) significantly increased the risk of ectopic pregnancy (OR 2.59; P = 0.0102).

CONCLUSIONS

Unfavourable uterine environment, including uterine pathologies, uterine or tubal surgery and suboptimal endometrial build-up were related to ectopic pregnancy. Low expansion grade of blastocysts was identified as an additional putative risk factor for ectopic pregnancy, indicating the importance of proper embryonal-maternal synchronization. The overall ectopic pregnancy rate after blastocyst transfer was low, comparable with reported ectopic pregnancy rates in spontaneous conceptions. Proper evaluation of tubal and uterine pathologies, optimizing endometrial preparation and the transfer of expanded blastocysts in a frozen embryo transfer cycle, might be beneficial.

Innovations in assisted reproductive technologies: impact on contemporary donor egg practice and future advances

Innovations in assisted reproductive technologies (ART) have driven progress in the donor egg field since the birth of the first baby derived from a donor egg in 1983. Over time, donor oocytes have become an increasingly used option for patients unable to conceive with autologous oocytes. In donor egg, the unique separation of the oocyte source and recipient uterus has created a model that has propelled advances in ART. Progressive ART innovations that have optimized the oocyte donor and resulting embryo include the following: evaluation of ovarian reserve, controlled ovarian hyperstimulation regimens that reduce the risk of ovarian hyperstimulation syndrome, blastocyst culture, oocyte cryopreservation, and preimplantation genetic testing. For donor egg recipients, methods to optimize the endometrium to maximize implantation include endometrial receptivity testing, immunologic donor-recipient matching, and increased understanding of the uterine microbiome.

GnRH antagonist versus long agonist protocols in IVF: a systematic review and meta-analysis accounting for patient type

BACKGROUND

Most reviews of IVF ovarian stimulation protocols have insufficiently accounted for various patient populations, such as ovulatory women, women with polycystic ovary syndrome (PCOS) or women with poor ovarian response, and have included studies in which the agonist or antagonist was not the only variable between the compared study arms.

OBJECTIVE AND RATIONALE

The aim of the current study was to compare GnRH antagonist protocols versus standard long agonist protocols in couples undergoing IVF or ICSI, while accounting for various patient populations and treatment schedules.

SEARCH METHODS

The Cochrane Menstrual Disorders and Subfertility Review Group specialized register of controlled trials and Pubmed and Embase databases were searched from inception until June 2016. Eligible trials were those that compared GnRH antagonist protocols and standard long GnRH agonist protocols in couples undergoing IVF or ICSI. The primary outcome was ongoing pregnancy rate. Secondary outcomes were: live birth rate, clinical pregnancy rate, number of oocytes retrieved and safety with regard to ovarian hyperstimulation syndrome (OHSS). Separate comparisons were performed for the general IVF population, women with PCOS and women with poor ovarian response. Pre-planned subgroup analyses were performed for various antagonist treatment schedules.

OUTCOMES

We included 50 studies. Of these, 34 studies reported on general IVF patients, 10 studies reported on PCOS patients and 6 studies reported on poor responders. In general IVF patients, ongoing pregnancy rate was significantly lower in the antagonist group compared with the agonist group (RR 0.89, 95% CI 0.82-0.96). In women with PCOS and in women with poor ovarian response, there was no evidence of a difference in ongoing pregnancy between the antagonist and agonist groups (RR 0.97, 95% CI 0.84-1.11 and RR 0.87, 95% CI 0.65-1.17, respectively). Subgroup analyses for various antagonist treatment schedules compared to the long protocol GnRH agonist showed a significantly lower ongoing pregnancy rate when the oral hormonal programming pill (OHP) pretreatment was combined with a flexible protocol (RR 0.74, 95% CI 0.59-0.91) while without OHP, the RR was 0.84, 95% CI 0.71-1.0. Subgroup analysis for the fixed antagonist schedule demonstrated no evidence of a significant difference with or without OHP (RR 0.94, 95% CI 0.79-1.12 and RR 0.94, 95% CI 0.83-1.05, respectively). Antagonists resulted in significantly lower OHSS rates both in the general IVF patients and in women with PCOS (RR 0.63, 95% CI 0.50-0.81 and RR 0.53, 95% CI 0.30-0.95, respectively). No data on OHSS was available from trials in poor responders.

WIDER IMPLICATIONS

In a general IVF population, GnRH antagonists are associated with lower ongoing pregnancy rates when compared to long protocol agonists, but also with lower OHSS rates. Within this population, antagonist treatment prevents one case of OHSS in 40 patients but results in one less ongoing pregnancy out of every 28 women treated. Thus standard use of the long GnRH agonist treatment is perhaps still the approach of choice for prevention of premature luteinization. In couples with PCOS and poor responders, GnRH antagonists do not seem to compromise ongoing pregnancy rates and are associated with less OHSS and therefore could be considered as standard treatment.

Increased Uterine NK cell numbers and perforin expression during the implantation phase in IVF Cycles with GnRH Antagonist Protocol

GnRH antagonist negatively affects endometrial receptivity in in vitro fertilization (IVF) cycles, however, its underlying mechanism remains unclear. To explore its target molecules, we studied endometria in the window phase of fixed GnRH antagonist, low-dose flexible GnRH antagonist, GnRH agonist long protocol, and untreated control groups. There were 384 differentially expressed genes (DEGs) in the fixed antagonist group with greater than twofold expression change compared with the control group and 197 DEGs between the fixed antagonist and agonist groups, the majority of which were associated with the natural killer (NK) cell-mediated cytotoxicity pathway. We then analysed the PRF1 and FASLG protein levels. The perforin level were significantly higher in both the antagonist groups than in other two groups, and was higher in the fixed antagonist group. Similarly, the uNK cell numbers were higher in the antagonist groups, and the highest uNK cell number occurred in the fixed group (p < 0.05). No significant differences existed in the Fas ligand levels and apoptosis rates among the three treatment groups, but were higher in the treatment groups than the control group. Together, these data indicate that GnRH antagonist may increase the uNK cell numbers and perforin expression, and this effect may be dose-dependent.

Gonadotrophin-releasing hormone antagonists for assisted reproductive technology

BACKGROUND

Gonadotrophin-releasing hormone (GnRH) antagonists can be used to prevent a luteinizing hormone (LH) surge during controlled ovarian hyperstimulation (COH) without the hypo-oestrogenic side-effects, flare-up, or long down-regulation period associated with agonists. The antagonists directly and rapidly inhibit gonadotrophin release within several hours through competitive binding to pituitary GnRH receptors. This property allows their use at any time during the follicular phase. Several different regimens have been described including multiple-dose fixed (0.25 mg daily from day six to seven of stimulation), multiple-dose flexible (0.25 mg daily when leading follicle is 14 to 15 mm), and single-dose (single administration of 3 mg on day 7 to 8 of stimulation) protocols, with or without the addition of an oral contraceptive pill. Further, women receiving antagonists have been shown to have a lower incidence of ovarian hyperstimulation syndrome (OHSS). Assuming comparable clinical outcomes for the antagonist and agonist protocols, these benefits would justify a change from the standard long agonist protocol to antagonist regimens. This is an update of a Cochrane review first published in 2001, and previously updated in 2006 and 2011.

OBJECTIVES

To evaluate the effectiveness and safety of gonadotrophin-releasing hormone (GnRH) antagonists compared with the standard long protocol of GnRH agonists for controlled ovarian hyperstimulation in assisted conception cycles.

SEARCH METHODS

We searched the Cochrane Menstrual Disorders and Subfertility Group Trials Register (searched from inception to May 2015), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, inception to 28 April 2015), Ovid MEDLINE (1966 to 28 April 2015), EMBASE (1980 to 28 April 2015), PsycINFO (1806 to 28 April 2015), CINAHL (to 28 April 2015) and trial registers to 28 April 2015, and handsearched bibliographies of relevant publications and reviews, and abstracts of major scientific meetings, for example the European Society of Human Reproduction and Embryology (ESHRE) and American Society for Reproductive Medicine (ASRM). We contacted the authors of eligible studies for missing or unpublished data. The evidence is current to 28 April 2015.

SELECTION CRITERIA

Two review authors independently screened the relevant citations for randomised controlled trials (RCTs) comparing different GnRH agonist versus GnRH antagonist protocols in women undergoing in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility and risk of bias, and extracted the data. The primary review outcomes were live birth and ovarian hyperstimulation syndrome (OHSS). Other adverse effects (miscarriage and cycle cancellation) were secondary outcomes. We combined data to calculate pooled odds ratios (ORs) and 95% confidence intervals (CIs). Statistical heterogeneity was assessed using the I(2) statistic. We assessed the overall quality of the evidence for each comparison using GRADE methods.

MAIN RESULTS

We included 73 RCTs, with 12,212 participants, comparing GnRH antagonist to long-course GnRH agonist protocols. The quality of the evidence was moderate: limitations were poor reporting of study methods.Live birthThere was no conclusive evidence of a difference in live birth rate between GnRH antagonist and long course GnRH agonist (OR 1.02, 95% CI 0.85 to 1.23; 12 RCTs, n = 2303, I(2)= 27%, moderate quality evidence). The evidence suggested that if the chance of live birth following GnRH agonist is assumed to be 29%, the chance following GnRH antagonist would be between 25% and 33%.OHSSGnRH antagonist was associated with lower incidence of any grade of OHSS than GnRH agonist (OR 0.61, 95% C 0.51 to 0.72; 36 RCTs, n = 7944, I(2) = 31%, moderate quality evidence). The evidence suggested that if the risk of OHSS following GnRH agonist is assumed to be 11%, the risk following GnRH antagonist would be between 6% and 9%.Other adverse effectsThere was no evidence of a difference in miscarriage rate per woman randomised between GnRH antagonist group and GnRH agonist group (OR 1.04, 95% CI 0.82 to 1.30; 33 RCTs, n = 7022, I(2) = 0%, moderate quality evidence).With respect to cycle cancellation, GnRH antagonist was associated with a lower incidence of cycle cancellation due to high risk of OHSS (OR 0.47, 95% CI 0.32 to 0.69; 19 RCTs, n = 4256, I(2) = 0%). However cycle cancellation due to poor ovarian response was higher in women who received GnRH antagonist than those who were treated with GnRH agonist (OR 1.32, 95% CI 1.06 to 1.65; 25 RCTs, n = 5230, I(2) = 68%; moderate quality evidence).

AUTHORS' CONCLUSIONS

There is moderate quality evidence that the use of GnRH antagonist compared with long-course GnRH agonist protocols is associated with a substantial reduction in OHSS without reducing the likelihood of achieving live birth.

Embryonic early-cleavage rate is decreased with aging in GnRH agonist but not inantagonist protocols

PURPOSE

The aim of this study was to evaluate the correlation between embryonic early-cleavage status and the age of patients receiving either a GnRH agonist long protocol or a GnRH antagonist protocol.

METHODS

This retrospective study included 534 patients undergoing a fresh cycle of oocyte retrieval and day-3 embryo transfer. Of the 534 patients treated, 331 received a GnRH agonist long stimulation protocol (GnRH agonist group) for ovarian stimulation and 203 patients received a GnRH antagonist protocol (GnRH antagonist group).

RESULTS

By logistic regression analysis, the rate of embryonic early-cleavage was significantly decreased with increasing age of women in the agonist (P < 0.001) but not in antagonist groups (P = 0.61). Based on the results of this study, maternal age is a critical factor for embryonic early-cleavage in agonist protocol but not in antagonist protocol. The results also showed that early-cleavage embryos were of better quality and resulted in a higher pregnancy rate than late-cleavage embryos in the GnRH agonist group. However, embryo quality and pregnancy rate was not significantly different between early and late cleavage embryos in the GnRH antagonist group.

CONCLUSIONS

We conclude that embryonic early-cleavage status is negatively correlated with aging in women receiving GnRH agonist long down-regulation but not in GnRH antagonist protocols. We also conclude that early cleavage of the zygote is not a reliable predictor for pregnancy potential using the GnRH antagonist protocol.

Implications of Blood Type for Ovarian Reserve and Infertility - Impact on Oocyte Yield in IVF Patients

Introduction: Diminished ovarian reserve (DOR) has been linked to certain subpopulations and distinct gene polymorphisms. It has even been hypothesized that the AB0 blood group system could be linked to ovarian reserve (OR) as reflected by early follicular phase follicle stimulating hormone (FSH) levels. Although estimation of OR is routinely done using levels of anti-Müllerian hormone (AMH), FSH, estradiol or inhibin B, the diagnostic accuracy of these markers is often limited. The aim of this study was to evaluate whether there is any correlation between IVF patients' AB0 blood group system and ART outcome. Methods: In this retrospective observational single-center study we investigated the outcome of 1889 IVF cycles carried out between 2005 and 2012 with regard to blood type and OR in different age groups (21-36 years and 37-43 years). The number of cumulus oocyte complexes (COCs) and metaphase II oocytes obtained after ovarian stimulation, fertilization rate (FR), pregnancy rate (PR) and birth rate (BR) were evaluated with respect to maternal age (21-36 and 37-43 years, respectively). Results: We found no significant differences in the average number of COCs after ovum pick-up in either of the age groups. Moreover, the mean number of MII oocytes and 2PN stages were similar for all blood type groups. As regards IVF outcome measured in terms of PR and BR, no significant differences were observed between the different blood groups. In conclusion, no correlation was found between blood type and female fertility. Discussion: The most precise definition of OR is determining the number of competent oocytes. Based on the finding of our study, the hypothesis that there is a correlation between OR and AB0 blood group system can be dismissed for Caucasian IVF patients.

Optimal usage of the GnRH antagonists: a review of the literature

Gonadotropin-releasing hormone (GnRH) antagonists, which became commercially available from 1999, have been used for the prevention of premature luteinizing hormone (LH) surges in controlled ovarian stimulation for in vitro fertilization or intracytoplasmic sperm injection. This review focuses on the recent literature on the use of GnRH antagonists and provides guidelines for optimal use in light of increasing evidence showing that GnRH antagonists are safe and effective, allowing flexibility of treatment in a wide range of patient populations. This includes patients undergoing first-line controlled ovarian stimulation, poor responders, and women diagnosed with polycystic ovary syndrome. The GnRH antagonist offers a viable alternative to the long agonists, providing a shorter duration of treatment with fewer injections and with no adverse effects on assisted reproductive technology outcome. This results in a significantly lower amount of gonadotropins required, which is likely to lead to improved patient compliance.

Gonadotrophin-releasing hormone antagonists for assisted reproductive technology

BACKGROUND

Gonadotrophin-releasing hormone (GnRH) antagonists can be used to prevent a luteinizing hormone (LH) surge during controlled ovarian hyperstimulation (COH) without the hypo-estrogenic side-effects, flare-up, or long down-regulation period associated with agonists. The antagonists directly and rapidly inhibit gonadotropin release within several hours through competitive binding to pituitary GnRH receptors. This property allows their use at any time during the follicular phase. Several different regimes have been described including multiple-dose fixed (0.25 mg daily from day six to seven of stimulation), multiple-dose flexible (0.25 mg daily when leading follicle is 14 to 15 mm), and single-dose (single administration of 3 mg on day 7 to 8 of stimulation) protocols, with or without the addition of an oral contraceptive pill. Further, women receiving antagonists have been shown to have a lower incidence of ovarian hyperstimulation syndrome (OHSS). Assuming comparable clinical outcomes for the antagonist and agonist protocols, these benefits would justify a change from the standard long agonist protocol to antagonist regimens. This is an update of a Cochrane review first published in 2001, and previously updated in 2006.

OBJECTIVES

To evaluate the effectiveness and safety of gonadotrophin-releasing hormone (GnRH) antagonists with the standard long protocol of GnRH agonists for controlled ovarian hyperstimulation in assisted conception cycle

SEARCH STRATEGY

We performed electronic searches of major databases, for example Cochrane Menstrual Disorders and Subfertility Group Specialised Register, CENTRAL, MEDLINE, EMBASE (from 1987 to April 2010); and handsearched bibliographies of relevant publications and reviews, and abstracts of major scientific meetings, for example the European Society of Human Reproduction and Embryology (ESHRE) and American Society for Reproductive Medicine (ASRM). A date limited search of Cochrane Menstrual Disorders and Subfertility Group Specialised Register, CENTRAL from April 2010 to April 2011 was run. Eighteen studies have been entered into the Classification pending references section of this update. These studies will be appraised for inclusion or exclusion in the next update of this review, due April 2012.

SELECTION CRITERIA

Two review authors independently screened the relevant citations for randomised controlled trials (RCTs) comparing different agonist versus antagonist protocols in women undergoing IVF or ICSI.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial risk of bias and extracted data. If relevant data were missing or unclear, the authors were contacted for clarification.

MAIN RESULTS

Forty-five RCTs (n = 7511) comparing the antagonist to the long agonist protocols fulfilled the inclusion criteria. There was no evidence of a statistically significant difference in rates of live-births (9 RCTs; odds ratio (OR) 0.86, 95% CI 0.69 to 1.08) or ongoing pregnancy (28 RCTs; OR 0.87, 95% CI 0.77 to 1.00). There was a statistically significant lower incidence of OHSS in the GnRH antagonist group (29 RCTs; OR 0.43, 95% CI 0.33 to 0.57).

AUTHORS' CONCLUSIONS

The use of antagonist compared with long GnRH agonist protocols was associated with a large reduction in OHSS and there was no evidence of a difference in live-birth rates.

GnRH antagonist, cetrorelix, for pituitary suppression in modern, patient-friendly assisted reproductive technology

BACKGROUND

Gonadotropin-releasing hormone (GnRH) analogues are used routinely to prevent a premature luteinizing hormone (LH) surge in women undergoing assisted reproductive technology (ART) treatments. In contrast to GnRH agonists, antagonists produce rapid and reversible suppression of LH with no initial flare effect.

OBJECTIVE

To review the role of cetrorelix, the first GnRH antagonist approved for the prevention of premature LH surges during controlled ovarian stimulation in modern ART.

METHOD

A review of published literature on cetrorelix.

RESULTS

Both multiple- and single-dose cetrorelix protocols were shown to be at least as effective as long GnRH agonist regimens for pituitary suppression in Phase II/III clinical trials. Furthermore, cetrorelix co-treatment resulted in similar live birth rates but a shorter duration of gonadotropin stimulation, a lower total gonadotropin dose requirement and lower incidence of ovarian hyperstimulation syndrome compared with long agonist regimens. A single-dose cetrorelix protocol further decreased the number of injections required. Preliminary studies have also produced promising data on the use of cetrorelix in modified ART protocols, such as frozen embryo transfer and donor oocyte recipient cycles.

CONCLUSION

Cetrorelix offers a potential therapeutic alternative to GnRH agonists during controlled ovarian stimulation and has become an integral part of modern, patient-friendly reproductive medicine.

Early-cleavage is a reliable predictor for embryo implantation in the GnRH agonist protocols but not in the GnRH antagonist protocols

BACKGROUND

To test if early-cleavage was a strong predictor of pregnancy in patients receiving either a GnRH agonist long protocol or a GnRH antagonist protocol for in-vitro fertilization treatment (IVF) and intracytoplasmic sperm injection (ICSI).

METHODS

This retrospective study included 534 patients undergoing a fresh cycle of oocyte retrieval and the day-3 embryo transfer (from 22 to 46 years old). Of the 534 patients treated, 331 received a GnRH agonist long stimulation protocol (GnRH agonist group) for ovarian stimulation and 203 patients received a GnRH antagonist protocol (GnRH antagonist group). In each group, patients who had at least one early-cleavage embryo transferred were designated as the 'early-cleavage' subgroup. Patients who had no early-cleavage embryos transferred were designated as the 'late-cleavage' subgroup.

RESULTS

The early cleavage rate was significantly lower in the GnRH antagonist group compared with that in the GnRH agonist group (IVF cycles: 34% versus 20%; ICSI cycles: 50% versus 37.8%, respectively, P < 0.0001). In the GnRH agonist group, the pregnancy rates were significantly higher in the early-cleavage subgroup than those in the late-cleavage subgroup (53.7% vs 33.9%, P < 0.0001). In the GnRH antagonist group, the pregnancy rates were not significantly different between the early-cleavage and late-cleavage subgroups (45.9% vs 43.8%, P > 0.05).

CONCLUSION

Early cleavage of zygote is not a reliable predictor for embryo implantation potential in using the GnRH antagonist protocol. Furthermore, the implantation rates between the GnRH agonist and GnRH antagonist groups were comparable.

Gonadotropin-releasing hormone agonist or human chorionic gonadotropin for final oocyte maturation in an oocyte donor program

OBJECTIVE

To compare leuprolide acetate to hCG as the trigger for final oocyte maturation in oocyte donor cycles.

DESIGN

Retrospective review.

SETTING

Academic IVF donor program.

PATIENT(S)

Thirty-two healthy oocyte donors aged 21-33 years with adequate ovarian reserve.

INTERVENTION(S)

Donors were down-regulated with cetrorelix and received either leuprolide acetate (n = 12) or hCG (n = 20) for final oocyte maturation.

MAIN OUTCOME MEASURE(S)

Embryo number, embryo quality, fertilization, implantation, clinical pregnancy, and ovarian hyperstimulation syndrome rates.

RESULT(S)

The numbers of total oocytes (23 vs. 15), mature (metaphase II) oocytes (22 vs. 13), embryos (15 vs. 10), and cryopreserved embryos (12 vs. 6) per treatment cycle were significantly greater in the leuprolide arm than in the hCG arm. Fertilization rates (73% vs. 78%), implantation rates (30% vs. 29%), and clinical pregnancy rates (40% vs. 50%) were not statistically different between the arms. There were no cases of ovarian hyperstimulation syndrome.

CONCLUSION(S)

Leuprolide acetate-triggered oocyte donor cycles yielded similar fertilization, implantation, and clinical pregnancy rates to hCG-triggered cycles.

Low-dose human chorionic gonadotropin during the proliferative phase may adversely affect endometrial receptivity in oocyte recipients

The effect of low-dose human chorionic gonadotropin (hCG) administration in the proliferative phase of oocyte recipients was investigated in a prospective randomized trial. Sibling oocytes from the same donor were shared at random among two different recipients. In group I oocyte recipients received 750 IU of hCG every three days concomitant to endometrial preparation with estradiol until hCG injection to the donor, whereas in group II recipients received no hCG during endometrial priming with estradiol. Endometrial thickness was significantly lower in group I compared with group II, although similar endometrial thickness was detected during the mock cycle. Pregnancy rates were significantly lower in group I than in group II (13.6% vs. 45.4%, p<0.05). Implantation rates were also significantly lower in group I (1.7% vs. 22.4%, p<0.01). The study was discontinued prematurely for ethical reasons when 22 cycles were completed, as pregnancy rates were very low in group I. In conclusion, hCG administration in the proliferative phase might directly affect endometrial proliferation and receptivity.

Prospective, randomized, comparative study of leuprorelin + human menopausal gonadotropins versus ganirelix + recombinant follicle-stimulating hormone in oocyte donors and pregnancy rates among the corresponding recipients

AIM

To compare the clinical pregnancy rate in recipients of oocytes from donors treated with leuprorelin + human menopausal gonadotropins (hMG) with that obtained when the donors were treated with ganirelix + recombinant follicle-stimulating hormone (rFSH). The secondary aim was to compare the donors' response to the two treatments.

METHOD

A prospective, randomized, comparative study was conducted between January 2005 and November 2006 in a private hospital. Donors were randomized to receive a long protocol of leuprorelin + hMG (group DI) or ganirelix + rFSH (group DII). Their respective recipients were randomized to group RI or group RII, respectively.

RESULTS

The characteristics of the donors were similar in both groups. More cycles were cancelled in group DI than in group DII (28.1% vs. 2.5%; p < 0.05). Compared with donors in group DII, the donors in group DI required a significantly higher dose of gonadotropins (2794 +/- 957 U vs. 1777 +/- 1043 U; p < 0.05) and more days of stimulation (11.7 +/- 2.3 vs. 9.5 +/- 1.5; p < 0.05); they also yielded fewer oocytes (15.0 +/- 6.1 vs. 17.9 +/- 8.6; p < 0.05). There were no differences in the characteristics of the recipients, in the fertilization rate or in the number of embryos transferred. The quality of transferred embryos was better in group RI (8.0 +/- 1.2 vs. 7.5 +/- 1.6; p < 0.05), and this group also achieved a better pregnancy rate per embryo transfer than did group RII (62.3% vs. 48.4%; p < 0.05).

CONCLUSIONS

Treating oocyte donors with leuprorelin + hMG produces among recipients a greater probability of clinical pregnancy per embryo transfer than when donors are treated with ganirelix + rFSH; however, more cycles are cancelled and the former treatment is more unpleasant for donors.

Serum cetrorelix concentrations do not affect clinical pregnancy outcome in assisted reproduction

OBJECTIVE

To analyze the potential association between serum cetrorelix levels and clinical pregnancy outcome in patients who had undergone assisted reproduction cycles with a GnRH antagonist cetrorelix acetate 3-mg injection.

DESIGN

Retrospective case-control study.

SETTING

University-affiliated private-assisted reproduction center.

PATIENT(S)

130 IVF and intracytoplasmic sperm injection first cycles, treated with the same cetrorelix acetate protocol, in two matched groups according to whether the cycle resulted in clinical pregnancy (n = 56) or not (n = 74).

INTERVENTION(S)

Cetrorelix acetate administration at 3 mg in a sandwich protocol.

MAIN OUTCOME MEASURE(S)

Serum cetrorelix concentrations on the day of hCG administration with regard to clinical pregnancy outcome, pre- versus post-hCG percent change in serum E(2) levels and implantation rates.

RESULT(S)

The cetrorelix serum concentrations were in the range of 0.29 to 5.12 ng/mL. The comparisons between groups with and without clinical pregnancy revealed comparable serum cetrorelix levels. There was no significant correlation between the serum cetrorelix concentrations and percent change in pre- versus post-hCG serum E(2) levels. Serum cetrorelix levels were comparable among patients with various implantation rates.

CONCLUSION(S)

Although a wide range of serum cetrorelix levels could be detected during a GnRH antagonist cycle, these levels were comparable in patients with and without clinical pregnancies.

Cryopreserved blastocyst transfer: impact of gonadotropin-releasing hormone agonist versus antagonist in the previous oocyte retrieval cycles

OBJECTIVE

To assess any detrimental effect of gonadotropin-releasing hormone (GnRH) antagonists on oocyte quality and embryo development by comparing the outcome of cryopreserved-thawed blastocyst transfers for cycles using a GnRH agonist or GnRH antagonist protocol for the controlled ovarian stimulation in the oocyte retrieval cycle.

DESIGN

Retrospective comparative study.

SETTING

Private IVF center.

PATIENT(S)

Seventy-seven women who underwent cryopreserved-thawed blastocyst transfer.

INTERVENTION(S)

The patients were divided into two groups based on whether they had been treated using a GnRH agonist long protocol (n = 44) or a GnRH antagonist multiple-dose protocol (n = 33) during the previous oocyte retrieval cycle. Cryopreserved-thawed blastocysts were transferred after endometrial preparation without pituitary suppression using a GnRH agonist.

MAIN OUTCOME MEASURE(S)

Implantation and clinical pregnancy rates.

RESULT(S)

The postthaw survival rate and numbers of good quality blastocysts transferred were similar for the GnRH agonist and GnRH antagonist groups. Implantation and pregnancy rates for cryopreserved-thawed blastocyst transfer for the GnRH agonist group versus the GnRH antagonist group were 21.0% (25 of 119) versus 29.0% (27 of 93) and 38.6% (17 of 44) versus 51.5% (17 of 33), respectively, which was not statistically significantly different.

CONCLUSION(S)

No difference was found in terms of implantation and pregnancy rates when a GnRH agonist or GnRH antagonist was used in the previous oocyte retrieval cycle. Our results suggest that GnRH antagonists do not have a detrimental effect on oocyte quality or embryo development.

Clinical outcomes using a flexible regimen of GnRH-antagonists and a 'step-up' of additional gonadotropins in donor oocyte cycles

OBJECTIVE

To assess the impact of serum estradiol upon oocyte donor cycle stimulation characteristics and clinical outcomes using flexible GnRH-antagonist (GnRH-ant) with additional FSH supplementation.

RESEARCH DESIGN AND METHODS

A retrospective chart review of 99 oocyte donor cycles using ovarian hyperstimulation with recombinant FSH (rFSH) and GnRH-ant was analyzed. Following discontinuation of oral contraceptives, controlled ovarian hyperstimulation was begun using rFSH (150-300 IU daily). GnRH-ant (ganirelix, Organon) and an additional 75 IU of FSH/day were begun when lead follicles were 13-14 mm in greatest diameter. Cycles were analyzed based on serum estradiol response following administration of GnRH-ant (Group 1: progressive rise and Group 2: no rise or a decline). Primary endpoints were cycle stimulation characteristics based on serum estradiol following GnRH-ant, clinical pregnancy and implantation rates.

RESULTS

A decline in serum estradiol was seen after GnRH-ant administration in 45% of cycles. Clinical pregnancy rates per transfer (70 vs. 72%) and implantation rates (43 vs. 56%) were similar for each group.

CONCLUSION

Flexible regimens of GnRH-ant even with additional rFSH in a 'step-up' fashion frequently result in a decline in serum estradiol during ovulation induction. While our study is non-randomized, it does not appear to result in any adverse affect in clinical outcomes in donor oocyte cycles.

In vitro maturation of oocytes collected from unstimulated ovaries for oocyte donation

OBJECTIVE

To assess the role of immature oocyte collection from unstimulated ovaries as a potential source of oocyte donation.

DESIGN

Prospective cohort study.

SETTING

A tertiary, university-based, in vitro fertilization center.

PATIENT(S)

Twelve oocyte donors with ultrasound-only polycystic ovaries or polycystic ovary syndrome matched with 12 oocyte recipients.

INTERVENTION(S)

Immature oocyte collection without any ovarian stimulation. In vitro maturation of the oocytes. Embryo transfer of the embryos.

MAIN OUTCOME MEASURE(S)

Immature oocyte collection, maturation, fertilization, and cleavage rates. Implantation, pregnancy, and live birth rates.

RESULT(S)

A mean of 12.8 +/- 5.1 Germinal-vesicle oocytes were aspirated per collection. The in vitro maturation rate was 68.3% +/- 18.4% with a mean of 8.7 +/- 3.6 mature oocytes per collection. The mean fertilization rate was 73.3% +/- 19.4%. Two to five embryos (median four) were transferred. Six recipients conceived, giving a 50% clinical pregnancy rate per cycle. The mean implantation rate per embryo was 18.2%. The live birth rate per cycle started was 30%.

CONCLUSION(S)

Collecting immature oocytes from unstimulated ovaries for the purpose of oocyte donation is a simple procedure that totally avoids ovarian stimulation. With appropriate selection of women with ultrasound-only polycystic ovaries or women with the polycystic ovary syndrome, the pregnancy rates of the recipients are comparable with those achieved through conventional IVF oocyte donor cycles.

A retrospective comparison of clinical outcomes and satisfaction using reconstituted recombinant gonadotropins (rFSH) or cartridge rFSH with a pen device in donor oocyte cycles

BACKGROUND

Use of recombinant follicle stimulating hormone (rFSH) in a cartridge pen device offers obvious benefits for donor oocyte cycles including the administration of fewer and more patient-friendly injectable medications.

METHODS

In a University-based IVF program, a total of 98 oocyte donor cycles using rFSH either reconstituted or as a pen device given to 118 recipients (eight split cycles) were retrospectively reviewed. Following discontinuation of oral contraceptive, controlled ovarian hyperstimulation was begun using either reconstituted rFSH (n = 19) or rFSH with a cartridge pen device (n = 79) (150-300 IU qd). GnRH-antagonists (Ganirelix, Organon) and an additional 75 IU of rFSH/day were begun when lead follicles were 13-14 mm in greatest diameter. The primary endpoints analyzed included cycle stimulation characteristics for each donor group and donor medication tolerance assessment with respect to each rFSH formulation, while secondary outcome measures included clinical pregnancy and implantation rates.

RESULTS

Oocyte donors using the pen required significantly less rFSH (2734 IU vs. 3276 IU, p < 0.05) and scored significantly higher medication tolerance scores (3.9 +/- 0.4 vs. 3.1 +/- 0.6, p < 0.05). No other differences in cycle stimulation for oocyte donors and clinical outcomes for recipients were seen including pregnancy rates (pen, 77% vs. reconstituted, 55%, p - NS) and clinical pregnancy rates (61% vs. 45%, p - NS). However, significantly greater implantation rates (57% vs. 31%, p < 0.01) occurred in the pen group.

CONCLUSION

Compared to reconstituted formulations, the pen device results in lower gonadotropin requirements and provides a simplified dosing method with better tolerance.

Similar outcome for cryopreserved embryo transfer following GnRH-antagonist/GnRH-agonist, GnRH-antagonist/HCG or long protocol ovarian stimulation

The pregnancy rates after triggering of final oocyte maturation with gonadotrophin-releasing hormone (GnRH) agonist in GnRH-antagonist ovarian stimulation protocols are lower than those following triggering with human chorionic gonadotrophin (HCG). Furthermore, lower pregnancy rates following GnRH-antagonist protocols compared with long GnRH-agonist protocols have been reported. The differences might be due to an impact on oocyte number and quality or on the endometrium. If any stimulation protocol had a negative impact on oocyte quality, then further evidence of this effect would be observed following frozen-thawed embryo transfer originating from that stimulation cycle. The outcome of frozen-thawed embryo transfer was retrospectively analysed using the long protocol with triptorelin depot 3.75 mg (n = 215) or 0.1 mg/day (n = 83), or GnRH-antagonist protocol with either HCG (n = 69) or GnRH-agonist (n = 25) for final oocyte maturation. The outcomes measured were implantation rate, clinical pregnancy rate, ongoing pregnancy rate and embryo survival rate. All outcomes were similar in the four groups. It is concluded that the potential for frozen-thawed embryos to implant and develop following transfer is independent of the GnRH-analogue and the final oocyte maturation protocol used in the collection cycle. Lower IVF embryo transfer success using GnRH-antagonist/GnRH-agonist protocol does not appear to be related to an adverse effect on oocyte quality.

In vivo characterization of a novel GnRH (gonadotropin-releasing hormone) antagonist, LXT-101, in normal male rats

LXT-101 is a newly developed GnRH (gonadotropin-releasing hormone) analogue. In this study, the in vivo pharmacological profile in intact male rats and binding characters of LXT-101 were illustrated, and regulation of mRNA of hormone receptors related to the pituitary-gonadal axis during and after administration was observed to reveal its molecular mechanism of potent effect and reversibility. After single subcutaneous injections, LXT-101 produced a dose- and time-dependent suppression of serum testosterone level. Multiple administrations and osmotic pump implantation revealed that the time of onset and dose needed to maintain the effect of chemical castration decreased as the frequency of injection increased and gave direct proof that depot formulation could significantly improve the duration of antagonist delivery and pharmacological activities compared to the injectable formulation. And LXT-101 showed excellent character of regulating the pituitary-gonadal axis quickly and reversibly. Competitive binding assay showed that LXT-101 could specifically bind a pituitary GnRH receptor with high affinity. These results indicated that LXT-101 is fit for sustained-release formulation and it might possibly be developed as an ideal candidate for treating sex hormone-sensitive tumors and other disorders.

Optimal stimulation protocols for in vitro fertilization

OBJECTIVE

To update clinicians on different gonadotropin regimens for ovarian stimulation for IVF including the use of urinary and recombinant gonadotropins, the value of added LH to FSH in the stimulation regimen, the use of GnRH agonists and antagonists, and the role of minimal stimulation protocols.

DESIGN

Literature review and critical analysis of major articles during the last five years on ovarian stimulation for IVF.

CONCLUSION(S)

Urinary and recombinant gonadotropins, for ovarian stimulation for IVF, are probably equally safe and effective. The higher cost for recombinant products limits their worldwide use in IVF. Conflicting data exist regarding the benefit of adding LH to FSH in the stimulation regimens. The use of different GnRH-agonists, of varying potency, may account for different levels of LH suppression. Adding LH should be considered in severe situations of LH suppression such as with the use of potent GnRH-agonists or when GnRH-antagonists are introduced during the course of stimulation. GnRH-antagonists provide advantages to patients in terms of fewer injections, shorter stimulation days, and avoidance of adverse effects of agonists. The incidence of ovarian hyperstimulation syndrome is probably less with antagonists compared to agonists, with the option to use an agonist as a surrogate LH surge. Fixed and early start of the antagonist is probably more effective than an individualized and late start. The earlier reported lower pregnancy rates with antagonists compared to agonists is not fully understood and needs to be continually monitored. Minimal stimulation protocols using a combination of clomiphene citrate and gonadotropins are attractive and should be considered in some patients owing to lower costs and acceptable success rates. The optimal stimulation protocol for IVF should be an individualized regimen based on the patient's ovarian physiology and prior IVF experience, if any.

Gonadotrophin-releasing hormone antagonists for assisted conception

BACKGROUND

Gonadotrophin-releasing hormone antagonists produce immediate suppression of gonadotrophin secretion, hence, they can be given after starting gonadotrophin administration. This has resulted in dramatic reduction in the duration of treatment cycle. Two different regimes have been described. The multiple-dose protocol involves the administration of 0.25 mg cetrorelix (or ganirelix) daily from day six to seven of stimulation, or when the leading follicle is 14 to15 mm, until human chorionic gonadotrophin (HCG) administration and the single-dose protocol involves the single administration of 3 mg cetrorelix on day seven to eight of stimulation. Assuming comparable clinical outcome, these benefits would justify a change from the standard long protocol of GnRH agonists to the new GnRH antagonist regimens.

OBJECTIVES

To evaluate the evidence regarding the efficacy of gonadotrophin-releasing hormone (GnRH) antagonists with the standard long protocol of GnRH agonists for controlled ovarian hyperstimulation in assisted conception.

SEARCH STRATEGY

We searched Cochrane Menstrual Disorders and Subfertility Group's Specialised Register, MEDLINE and EMBASE databases from 1987 to February 2006, and handsearched bibliographies of relevant publications and reviews, and abstracts of scientific meetings. We also contacted manufacturers in the field.

SELECTION CRITERIA

Randomized controlled studies comparing different protocols of GnRH antagonists with GnRH agonists in assisted conception cycles were included in this review.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. If relevant data were missing or unclear, the authors have been consulted

MAIN RESULTS

Twenty seven RCTs comparing the GnRH antagonist to the long protocol of GnRH agonist fulfilled the inclusion criteria. Clinical pregnancy rate was significantly lower in the antagonist group. (OR = 0.84, 95% CI = 0.72 - 0.97). The ongoing pregnancy/ live-birth rate showed the same significant lower pregnancy in the antagonist group (P = 0.03; OR 0.82, 95% CI 0.69 to 0.98).However, there was statistically significant reduction in incidence of severe OHSS with antagonist protocol. The relative risk ratio was (P = 0.01; RR 0.61, 95% CI 0.42 to 0.89). In addition, interventions to prevent OHSS (e.g. coasting, cycle cancellation) were administered more frequently in the agonist group (P = 0.03; OR 0.44, 95% CI 0.21 to 0.93).

AUTHORS' CONCLUSIONS

GnRH antagonist protocol is a short and simple protocol with good clinical outcome with significant reduction in incidence of severe ovarian hyperstimulation syndrome and amount of gonadotrophins but the lower pregnancy rate compared to the GnRH agonist long protocol necessitates counseling subfertile couples before recommending change from GnRH agonist to antagonist..

Ovarian stimulation with GnRH agonist, but not GnRH antagonist, partially restores the expression of endometrial integrin 3 and leukaemia-inhibitory factor and improves uterine receptivity in mice

BACKGROUND

The impact of different ovarian stimulation (OS) protocols on endometrial receptivity remains controversial. In this study, the effects of different OS on the expression of endometrial integrin beta3 subunit and leukaemia-inhibitory factor (LIF) during the implantation window and the implantation rate in mice were investigated.

METHODS

Three OS protocols were used, involving either pregnant mare's serum gonadotrophin (PMSG) alone, PMSG plus GnRH agonist or PMSG plus GnRH antagonist. Uterus samples were collected at 48 h after OS or ovulation and were detected with immunohistochemistry, Western blot and RT-PCR analyses. Normal embryos at gestation day 4 were transferred into the uteri of mice in the control and OS groups.

RESULTS

All OS groups showed a significant decrease in the expression of both the endometrial integrin beta3 subunit and LIF during the implantation window and the implantation rate. Among the three OS groups, GnRH agonist-treated mice showed a higher endometrial integrin beta3 subunit and LIF expression and a higher implantation rate. No significant difference was found in the measured indices between the GnRH antagonist and PMSG groups.

CONCLUSIONS

OS may inhibit the expression of endometrial integrin beta3 subunit and LIF and impair endometrial receptivity in mice. OS with GnRH agonist, but not GnRH antagonist, may partially restore the endometrial physiological secretion and improve uterine receptivity.