High Maternal Serum Estradiol Environment in the First Trimester Is Associated With the Increased Risk of Small-for-Gestational-Age Birth

Context: There are increasing concerns that a disrupted endocrine environment may disturb the growth of the fetus. Assisted reproductive technology (ART) situates gamete/embryo in a supraphysiological estradiol (E2) environment and, thus, provides an ideal model to investigate this problem. Objective: Our objective was to investigate whether the maternal high-E2 environment in the first trimester increases the risks of low birth weight (LBW) and small-for-gestational-age (SGA) birth. Methods: In total, 8869 singletons born after fresh embryo transfer (ET) (n = 2610), frozen ET (n = 1039), and natural conception (NC) (n = 5220) and their mothers were included. Birth weight, LBW, SGA, and maternal serum E2 levels were investigated. Results: The mean serum E2 levels of women undergoing fresh ET at 4 and 8 weeks of gestation were significantly higher than those of the women undergoing frozen ET and the women with NC (P < .01). Serum E2 levels of women undergoing fresh ET at 4 and 8 weeks of gestation were pos...