Supraphysiological estradiol level in ovarian stimulation cycles affects the birthweight of neonates conceived through subsequent frozen-thawed cycles: a retrospective study.

Abstract

To investigate whether supraphysiological estradiol (E₂ ) in controlled ovarian stimulation (COS) cycles affects the subsequent frozen-thawed embryo transfer (FET) in terms of the neonatal birthweight. Retrospective cohort study. University affiliated hospital. In all, 2066 patients undergoing FET cycles that resulted in live singleton births between July 2011 and Dec 2016. None. Multivariable linear regression and logistic regression was used to evaluate the association between peak E₂ and birthweight outcomes. Birthweight, z-score adjusted for gender and gestational age, and incidence of small-for-gestational-age (SGA) and low birthweight (LBW) in singleton neonates derived from FET cycles. Adjusted for confounding factors, both the absolute birthweight and the z-score of singletons following FET were negatively associated with peak E₂ levels in COS. In comparison with the referent category (E₂  ≤1500 pg/ml), the categories with E₂  >3000 pg/ml had a significantly lower z-score. The difference (95% CI) in estimated marginal mean of birthweights between referent category and highest E₂ (>8000 pg/ml) category was 104.57 g (18.13-181.06). Multiple logistic regression analyses showed that the adjusted odds ratio (95% CI) for SGA and LBW in term singletons comparing patients with E₂  >3000 pg/ml with those with E₂  ≤3000 pg/ml was 2.44 (1.37-4.34) and 2.32 (1.01-5.40), respectively. Peak E₂ levels in COS cycles are negatively associated with the birthweight of singletons conceived through subsequent FET cycles. The birthweight following FET is affected by previous COS cycle.