Fetoplacental ratio (FPR), the ratio of birthweight (BW) to placental weight (PW), indicates placental efficiency. Changes in FPR are linked to poor pregnancy outcomes and child health risks. Bisphenols and phthalates are endocrine disruptors found in plastics and personal care products that can cross the placenta and have been linked to pregnancy complications and adverse child health outcomes. We examined prenatal exposure to these chemicals in relation to FPR as a possible explanation for these risks. Our analysis included 393 participants in the New York University Children’s Health and Environment Study with data on prenatal chemical exposure, BW, and PW from singleton live births. We calculated molar sums of bisphenols and of metabolites of low and high molecular weight (LMW, HMW) phthalates, diethylhexyl phthalate (DEHP), and antiandrogenic phthalates. Linear regression models were adjusted for maternal age, prepregnancy BMI, parity, gestational age at delivery, and fetal sex. Analyses were stratified by fetal sex. HMW were positively associated with FPR in the combined fetal sex sample (beta=0.26, 0.01, 0.50) with a similar trend for DEHP and antiandrogenic phthalates (betas=0.21 -0.04, 0.45 and 0.21 -0.04, 0.45, respectively). Stratified analyses revealed that these results were driven by females, among whom LMW were also associated with higher FPR (beta=0.23 0.003, 0.45). No associations were observed between chemicals and BW in either combined or sex-stratified models. In contrast, HMW, LMW, DEHP, di-n-octylphthalate and bisphenols had negative associations with PW, suggesting placental growth as a target for phthalate-mediated endocrine disruption. • Phthalates associated with higher fetoplacental ratio, lower placental disc weight. • Associations varied by sex, with results being driven by female fetuses. • No associations were observed with birthweight. • Phthalates were linked to restricted placental growth, not placental efficiency.
Bommireddipalli et al. (2026) studied this question.