Midpregnancy Phthalate and Phenol Biomarkers in Relation to Infant Body Composition: The Healthy Start Prospective Cohort

BACKGROUND: Gestational phthalate and phenol exposure disrupts adipogenesis, contributing to obesity in mice. Whether gestational phthalate or phenol exposure is associated with infant body composition has not been investigated in humans. OBJECTIVE: We examined associations between biomarkers of phthalate and phenol exposure in midpregnancy and infant size and body composition at birth and at 5 months of age. METHODS: Analyses were conducted among 438 infants from the Healthy Start prospective pregnancy cohort. Sixteen phthalate and phenol biomarkers were quantified in spot urine samples collected at 24–28 wk of gestation. Infant outcomes measured at birth and at 5 months of age included size [weight (in grams)] and body composition [fat and lean masses (in grams); percentage fat mass]. Single- (linear) and multipollutant (quantile g-computation) models were used to estimate associations of phthalate and phenol biomarkers with infant outcomes at birth and at 5 months of age. Models were adjusted for sociodemographics, sample collection timing, and lifestyle factors and used to examine for effect modification by infant sex. RESULTS: In single-pollutant models, mono-benzyl phthalate and di- [Formula: see text]-butyl phthalate were inversely associated with percentage fat mass [[Formula: see text]: [Formula: see text] (95% CI: [Formula: see text] , [Formula: see text]) and [Formula: see text] (95% CI: [Formula: see text] , 0.01), respectively] in male but not female infants at birth. Similar, but less precise, associations were observed at 5 months of age. In multipollutant models, a 1-quartile increase in the phthalate and phenol biomarker mixture was inversely associated with percentage fat mass at birth [[Formula: see text] (95% CI: [Formula: see text] , 0.1)] and at 5 months of age [[Formula: see text] (95% CI: [Formula: see text] , [Formula: see text])] among males, but associations were null among females [0.48 (95% CI: [Formula: see text] , 1.75) and [Formula: see text] (95% CI: [Formula: see text] , 1.41), respectively]. Similar associations were observed with infant weight. CONCLUSION: In this U.S.-based prospective cohort, gestational phthalate and phenol biomarkers were inversely associated with infant weight and fat mass, particularly in males. https://doi.org/10.1289/EHP12500