Maternal Plasma per- and Polyfluoroalkyl Substance Concentrations in Early Pregnancy and Maternal and Neonatal Thyroid Function in a Prospective Birth Cohort: Project Viva (USA)

BACKGROUND: Prenatal exposure to some per- and polyfluoroalkyl substances (PFASs) may disrupt maternal and neonatal thyroid function, which is critical for normal growth and neurodevelopment. OBJECTIVES: We examined associations of PFAS exposure during early pregnancy with maternal and neonatal thyroid hormone levels. METHODS: We studied 732 mothers and 480 neonates in Project Viva, a longitudinal prebirth cohort in Boston, Massachusetts. We quantified six PFASs, including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), and maternal thyroid hormones [thyroxine ([Formula: see text]), Free [Formula: see text] Index ([Formula: see text]), thyroid stimulating hormone (TSH)] in plasma samples collected at a median 9.6 wk gestation and neonatal [Formula: see text] levels from postpartum heel sticks. We estimated associations of PFAS concentrations with thyroid hormone levels using covariate-adjusted linear regression models and explored effect measure modification by maternal thyroid peroxidase antibody (TPOAb) status and infant sex. RESULTS: PFAS concentrations were not associated with maternal [Formula: see text] , but PFOA, perfluorohexane sulfonate (PFHxS), and 2-(N-methyl-perfluorooctane sulfonamido) acetate (MeFOSAA) were inversely associated with maternal [Formula: see text] [e.g., [Formula: see text] (95% confidence interval (CI): [Formula: see text] , [Formula: see text]) per interquartile (IQR) increase in PFOA]. PFAS concentrations [PFOA, PFOS, and perfluorononanoate (PFNA)] were inversely associated with TSH levels in TPOAb-positive women only. Prenatal PFOS, PFOA, and PFHxS concentrations were inversely associated with [Formula: see text] levels in male [e.g., PFHxS, quartile 4 vs.1: [Formula: see text] (95% CI: [Formula: see text] , [Formula: see text] )], but not female neonates [[Formula: see text] (95% CI: [Formula: see text] , 1.79)]. CONCLUSIONS: In this study, prenatal exposure to some PFASs during early pregnancy was inversely associated with maternal [Formula: see text] and neonatal [Formula: see text] in male infants. These results support the hypothesis that prenatal exposure to PFASs influences thyroid function in both mothers and infants. https://doi.org/10.1289/EHP2534