Serum progesterone concentration and live birth rate in frozen-thawed embryo transfers with hormonally prepared endometrium

Research question: Is serum progesterone measurement on the day of embryo transfer associated with outcome of frozen-thawed embryo transfer (FET) in cycles using hormonal replacement therapy (HRT) for endometrium preparation? Design: This single-centre retrospective study assessed the relationship between serum progesterone on embryo transfer day and live birth rates in 227 FET cycles. Endometrial preparation was performed by sequential administration of vaginal oestradiol until endometrial thickness was >7 mm, followed by transdermal oestradiol combined with 600 mg vaginal micronized progesterone. Results: Mean serum embryo transfer day progesterone was 11.4 ng/ml. Serum progesterone <10 ng/ml was observed in 37% of cycles and was associated with significantly lower pregnancy (34% versus 48%, P = 0.04) and live birth rates (17% versus 31%, P = 0.01). Multivariate logistic regression analysis identified serum embryo transfer day progesterone as a significant prognostic factor for live birth rate (odds ratio [OR]: 2.75, 95% confidence interval [CI]: 1.40-5.43]). Receiver operator curve analysis for live birth rates by serum progesterone levels on embryo transfer day gave an area under the curve of 0.62 (95% CI: 0.53-0.72). Conclusions: The data show that serum progesterone concentration is associated with live birth rate. This outlines the importance of measuring serum progesterone in FET with HRT although progesterone monitoring is not usually performed in routine practice. However, the optimal timing for measurement and further adaptive management in the presence of low values remain to be determined.