Maternal Urinary Bisphenol a during Pregnancy and Maternal and Neonatal Thyroid Hormone Concentrations

Abstract

Bisphenol A (BPA) is an endocrine disruptor present in many consumer products. Experimental and epidemiologic evidence suggest that BPA disrupts thyroid function. The only prior epidemiologic study of prenatal BPA exposure reported sex-specific effects on thyroid hormones (THs). We examined associations between BPA and THs using multivariable linear regression in the Health Outcomes and Measures of the Environment Study (2003- 2006, Cincinnati, Ohio), a prospective birth cohort. Maternal urinary BPA concentration was measured at approximately 16 and 26 weeks gestation. Free and total thyroxine (T4) and thyroid stimulating hormone (TSH) concentrations were measured in maternal serum at approximately 16 weeks (n=185) and in cord serum (n=252). Separate models were built for a) 16 weeks, b) 26 weeks, and c) 16 and 26 weeks average urinary BPA. We found no associations between 16-week BPA concentration and maternal THs, and between any of the BPA measurements and cord T4. In contrast, each 10-fold increase in average maternal urinary BPA was associated with decreased cord TSH in female newborns (percent change=-31%; 95% confidence interval (CI):-49, -8%) but not males (3%; 95% CI:-26, 42%; p for effect modification=0.04). The 16-week BPA concentration was not associated with TSH (females:-7%; 95% CI:-32, 28%; males:-2%; 95% CI:-33, 42%; p for effect modification=0.87). In contrast, 26-week maternal urinary BPA was associated with reduced TSH for females (-43%; 95% CI:-60, -18%) but not males (-1%; 95% CI:-20, 24%; p for effect modification=0.01). We did not observe associations between BPA and maternal THs during pregnancy or newborn T4. In contrast with one prior study reporting reduced TSH among male newborns only, our findings suggest that prenatal BPA exposure may reduce TSH among female newborns. Consistent with the prior study, maternal BPA exposure later in pregnancy may have greater influence on newborn TSH than in early pregnancy.