The effect of gonadotrophin-releasing hormone agonist versus human chorionic gonadotrophin trigger on pregnancy and neonatal outcomes in Letrozole-HMG IUI cycles

Background GnRHa and hCG are both used for oocyte maturation and ovulation triggering. However, GnRHa have a shorter half-life than hCG, which leads to luteal phase deficiency. Letrozole (LE) has been found to improve the luteal function. Thus, the choice of triggering strategy can be different in intrauterine insemination (IUI) cycles using LE and human menopausal gonadotropin (HMG). The aim of this study was to compare the pregnancy and neonatal outcomes of patients triggered with GnRHa versus hCG versus dual trigger in LE-IUI cycles. Methods This retrospective cohort study included 6,075 LE-HMG IUI cycles between January 2010 and May 2021 at a tertiary-care academic medical center in China. All cycles were divided into three groups according to different trigger strategies as hCG trigger group, GnRHa trigger group and dual trigger group. The primary outcome was clinical pregnancy rate. Logistic regression analysis was performed to explore other risk factors for clinical pregnancy rate. Results No significant difference was observed in clinical pregnancy rate between hCG, GnRHa and dual trigger cycles in LE-HMG IUI cycles ( P = 0.964). The miscarriage rate was significantly lower in the GnRHa trigger group, and higher in the dual trigger group, compared with the hCG group ( P = 0.045). Logistic analysis confirmed that triggering strategy was associated with miscarriage (aOR:0.427, 95%CI: 0.183–0.996, P = 0.049; aOR:0.298, 95%CI: 0.128–0.693, P = 0.005). No significant differences were observed regarding neonatal outcomes between the three groups. Conclusions Our findings suggested that both GnRHa and dual trigger can be used to trigger ovulation in LE-HMG IUI cycles, but dual trigger must be used with caution.