P-639 Are GnRH-agonists (GnRH-a) safer and more effective ovulation triggers than human chorionic gonadotrophin (hCG)? A retrospective analysis of frozen embryo replacement cycle (FERC) outcomes
Authors: Turkay G , Rattos A , Besi D , Mittal M 
Published: July 2024

Study question

Are GnRH-agonists (GnRH-a) safer and more effective ovulation triggers than human chorionic gonadotrophin (hCG)? A retrospective analysis of frozen embryo replacement cycle (FERC) outcomes

Summary answer

GnRH-a trigger reduces the incidence and severity of ovarian hyperstimulation syndrome (OHSS) leading to significantly improved clinical outcomes when compared to hCG trigger for FERCs.

What is known already

Ovulation induction plays a crucial role in the success and safety of ART cycles. hCG is extensively used as an alternative to LH to trigger ovulation. However, high levels of sustained hCG exposure increases the risk of OHSS, a potentially life-threatening complication of ART. To eliminate the risk and incidence of OHSS, GnRH-a can be used to trigger ovulation. Although there are concerns regarding clinical outcomes with fresh transfers following GnRH-a trigger, it elicits a more physiological response compared to hCG. This may lead to improved embryo quality, utilisation, and better clinical outcomes following a freeze-all strategy, reducing patients’ time-to-pregnancy.

Study design, size, duration

This was a retrospective data analysis of FERC outcomes following fresh IVF or ICSI cycles, involving ovulation induction using either hCG or GnRH-a as a final trigger. The evaluation included results from cycles spanning an eight-year period, from January 2012 to December 2019 at Hammersmith Hospital London. A total of 160 cycles were included in the study, with 76 in the hCG trigger group and 84 in the GnRH-a trigger group.

Participants/materials, setting, methods

Strict inclusion criteria were employed to render the study groups as comparable as possible and to minimise the effect of independent variables, such as oocyte and sperm factors, on oocyte or embryo developmental competence. Inclusion criteria: women ≤37 years old at the start of treatment, GnRH antagonist stimulation, blastocyst vitrification-warming and transfers only. Statistical significance was calculated using independent t-test and Fisher’s Chi-square exact test.

Main results and the role of chance

The mean age (±SD) of patients at the time of oocyte retrieval was comparable across groups. The average number of oocytes collected were significantly higher in the GnRH-a group compared to hCG (28.31 vs. 18.07, respectively, P &lt; 0.001). Embryological data (maturation, fertilisation, blastocyst formation, blastocyst utilisation and good quality blastocyst formation rates) were comparable across both groups. OHSS rate was significantly lower in the GnRH-a group (17% vs. 50%. P &lt; 0.0001). The following clinical data were significantly higher (P &lt; 0.05) in the GnRH-a group compared to hCG: implantation rate (56% vs. 36%), clinical pregnancy rate (56% vs. 36%) and live birth rate (42% vs. 27%).

Limitations, reasons for caution

The biggest limitation of this study is its retrospective nature and the application of various inclusion-exclusion criteria that have resulted in relatively small sample sizes. Additionally, numerous other confounders, e.g. patient body mass index, cause/duration of infertility and stimulation duration, have not been considered in this study.

Wider implications of the findings

The findings of this study are promising and demonstrate a great potential for benefit in the use of GnRH-a trigger with a freeze-all strategy to minimise the risk of OHSS, diminishing the associated patient morbidity and mortality, reducing healthcare costs, improving clinical outcomes, and reducing the overall time-to-pregnancy for patients.

Trial registration number

not applicable