Abstract

Objective: To investigate factors associated with low serum progesterone levels on the day of frozen-thawed embryo transfer (FET) in cycles of endometrial preparation using exogenous hormonal regimens.

Methods: A cross-sectional descriptive study was conducted on 342 FET cycles at the Center for Assisted Reproductive Technology, Center of Obstetrics and Gynecology, Hue Central Hospital, from June 2023 to June 2025.

Results: The mean endometrial thickness prior to progesterone administration was 9,89 ± 1,06 mm. The proportion of FET cycles with low serum progesterone levels (<10 ng/mL) on the day of embryo transfer was 38,01%, with a mean progesterone concentration of 11,87 ± 5,20 ng/mL (range 0,50-60,0 ng/mL). Univariate and multivariate GEE regression analyses showed no significant association between general characteristics, obstetric history, infertility history, or FET cycle characteristics and serum progesterone levels on the day of embryo transfer in the study population (p > 0,05).

Conclusion: The endometrial preparation protocol plays a crucial role in optimizing outcomes of frozen-thawed embryo transfer cycles.