Lower serum LH level was related to poor embryo quality and adverse pregnancy outcomes in fixed GnRH antagonist protocol with estradiol pretreatment.

Objective: To disclose the relationships between serum LH and reproductive outcomes in Gonadotropin-releasing hormone (GnRH) antagonist protocol pretreated with luteal estradiol.

Methods: 371 patients, pretreated with estradiol, followed the GnRH antagonist protocol. They were divided into four groups based on the quartiles of serum LH levels on the day of gonadotropin (Gn) initiation(LH_GI) and trigger (LH_trigger). Data on various pregnancy outcomes were collected.

Results: As serum LH_GI increased, anti-Müllerian hormone (AMH) level, antral follicle count (AFC), LH_trigger, estradiol (E₂) and P on the trigger day, E₂/oocytes, and oocyte numbers increased and peaked in Q4, while Gn dose decreased. Good-quality embryo and blast formation rates increased and peaked in Q3. LH_GI <3.93 mIU/ml impaired ongoing pregnancy rate and LBR. After adjusting for AMH and AFC, the impacts were not significant. As LH_trigger increased, E₂/oocytes and good-quality embryo rate increased and peaked in T4 and implantation rate increased and peaked in T3. LH_trigger <1.49 mIU/ml independently influenced clinical pregnancy rate (CPR) after adjusting for AMH and AFC. LH_GI was positively related to AMH, AFC, LH_trigger, blast formation rate and negatively related to BMI, age and Gn dose. LH_trigger was positively related to E2/oocytes and good quality embryo rate.

Conclusions: Lower serum LH represents as a potential indicator for embryo quality and reproductive outcomes in GnRH antagonist fixed protocol pretreated with estradiol. Early identification of excessive suppression of LH levels will benefit individuals with normal ovarian reserve more.