Clinical impact of endogenous luteinizing hormone in frozen-thawed embryo transfer during hormone replacement cycle without gonadotropin-releasing hormone analog coadministration: Effects on pregnancy outcomes.

PURPOSE: To assess the correlation between serum luteinizing hormone (LH) levels preceding luteal replacement initiation and outcomes of frozen-thawed embryo transfer (FET) cycles during hormone replacement therapy (HRT) without co-administration of gonadotropin-releasing hormone (GnRH) analog.

METHODS

We retrospectively enrolled 490 FET cycles performed between March 2018 and May 2023. Patients were categorized into quartiles based on their serum LH levels preceding luteal replacement. Multivariate logistic regression analysis was performed, with clinical pregnancy and live birth rates as dependent variables. The independent variables included women's mean age, serum LH, and estradiol levels preceding luteal replacement, and endometrial thickness during transfer.

RESULTS

Mean age, serum estradiol, and LH levels preceding luteal replacement were 36.8 ± 0.2 years, 306.5 ± 7.7 pg/mL, and 10.3 ± 0.3 mIU/mL, respectively. The clinical pregnancy and live birth rates were 46.8% and 31.9%, respectively, and varied significantly between quartiles. Multivariate analysis revealed that younger age and higher LH levels were significantly associated with increased clinical pregnancy and live birth rates.

CONCLUSIONS

Endogenous LH may facilitate pregnancy within FET cycles under HRT without GnRH analogs by preparing the endometrium for implantation.