Prenatal Phthalate Exposure and Child Weight and Adiposity from in Utero to 6 Years of Age

BACKGROUND: Prenatal phthalate exposure has been associated with lower birth weight but also higher weight in childhood. Few studies have examined weight or adiposity from birth to childhood and thus cannot assess growth trajectories associated with exposure. OBJECTIVE: We assessed associations between maternal phthalate exposures in pregnancy and child weight and adiposity measured prenatally through childhood (3–6 years of age). METHODS: Within The Infant Development and the Environment Study (TIDES), a prospective pregnancy cohort, we analyzed a panel of phthalate metabolites in urine collected at two visits from early and late gestation ([Formula: see text]). We estimated average phthalate metabolite associations with child weight [Formula: see text]-scores from [Formula: see text] gestation (estimated by ultrasound), birth, and 1, 3, 4, and 6 years of age using linear mixed-effects (LME) models. We also modeled associations with adiposity [Formula: see text]-scores from birth (weight for length) and 1, 3, 4, and 6 years of age [body mass index (BMI)] using LME models. RESULTS: For weight, we observed inverse associations between several phthalate metabolites and birth weight [Formula: see text]-scores, but no associations were observed with postnatal weight [Formula: see text]-scores in LME models. Regarding adiposity, we observed inverse associations between phthalate metabolites and weight-for-length [Formula: see text]-scores at birth, but positive associations were observed with BMI [Formula: see text]-scores at 3–4 years of age in LME models. For example, mono-ethyl phthalate was associated with a 0.17-unit decrease in birth weight-for-length [Formula: see text]-score [95% confidence interval (CI): [Formula: see text] , [Formula: see text]] and a 0.18-unit increase in 4-years-of-age BMI [Formula: see text]-score (95% CI: 0.04, 0.32). DISCUSSION: We observed associations between prenatal exposure to phthalates and lower weight at birth but not at childhood follow-up visits. However, for adiposity, we observed an interesting pattern of association with low adiposity at delivery as well as high adiposity at 3–4 years of age. Although it is not clear from our results whether these associations occur within the same children, such a pattern of adiposity in early life has been linked to cardiometabolic disease in adulthood and deserves special attention as an outcome in the study of prenatal exposures in the developmental origins of health and disease. https://doi.org/10.1289/EHP10077