Association between serum estradiol levels prior to progesterone administration in artificial frozen-thawed blastocyst transfer cycles and live birth rate: a retrospective study.

OBJECTIVE To study whether serum estradiol (E2) levels prior to progesterone administration in the artificial endometrial preparation (AEP) of frozen-thawed blastocyst transfer affect the live birth rate. DESIGN Retrospective cohort study. SETTING Tertiary-care academic medical centre. POPULATION A total of 3857 frozen-thawed blastocyst transfer cycles were divided into three groups: <200 pg/ml (n = 1676); 200-399 pg/ml (n = 1296); and ≥400 pg/ml (n = 885), based on the 25th (182.3 pg/ml) and 75th percentile (390.2 pg/ml) of serum E2 level prior to progesterone administration. METHODS Univariable and multivariable logistic regression analysis was performed. MAIN OUTCOME MEASURES The primary outcome of the study was the live birth rate and the secondary outcomes included clinical pregnancy rate, pregnancy loss rate, neonatal birthweight, Z-score, and small for gestational age (SGA). RESULTS Compared with the reference group, accounting for major covariates, the live birth rate significantly decreased in the '≥400 pg/ml' group (adjusted OR 0.71, 95% CI 0.59-0.85). Compared with the reference group, there was an association between the E2 level in the '≥400 pg/ml' group and a decrease in the clinical pregnancy rate (adjusted OR 0.74, 95% CI 0.61-0.89). Compared with the reference group, the pregnancy loss rate significantly increased in the '≥400 pg/ml' group (adjusted OR 1.45, 95% CI 1.08-1.93). The E2 levels did not affect neonatal birthweight, Z-score, and SGA among singletons. CONCLUSIONS High serum E2 levels prior to progesterone administration in AEP are associated with a decreased live birth rate after frozen-thawed blastocyst transfer. TWEETABLE ABSTRACT High serum E2 levels prior to progesterone administration in artificial FET are associated with a decreased live birth rate after frozen-thawed blastocyst transfer.