Impact of serum progesterone level on the day of embryo transfer on live birth rate after single frozen-thawed blastocyst transfer in hormone replacement therapy cycles

Purpose

As the number of frozen-thawed embryo tryansfer cycles with Hormonal Replacement Therapy increases, the issue of the optimal progesterone level to ensure maximal success rates becomes critical. In this study, we aimed to determine the respective relevance of the 3 recently reported progesterone thresholds using an original statistical method.

Methods

This single-center retrospective study was conducted in a University-based Hospital in France in all consecutive single frozen thawed blastocyst transfers (SFBT) performed with HRT protocol in 2021. Progesterone levels were measured on the morning of the transfer. Patients were divided into deciles based on their progesterone levels on the day of SFBT, and outcomes were calculated for each decile. Multivariate logistic regression models were constructed to measure the association of these thresholds with clinical pregnancy rate and live birth rate (LBR), adjusting for demographic and clinical factors.

Results

A total of 256 cycles were included in the analysis. Clinical pregnancy rate was 30.1%, and live birth rate (LBR) was 29.3%. An inverted U curve was observed for the Positive Predictive Value of a LB, as it increases up to a peak around 11 ng/ml (optimal interval 10.5-12 ng/ml), before decreasing for high serum progesterone levels (>13 ng/ml).

Conclusions

Our study, aligned with recent literature, identified a positive relationship between progesterone levels on the day of SFBT in HRT and the positive predictive value of a live birth, the "ideal window" of progesterone on the day of FET being 10.5-12 ng/mL.