Prenatal Exposure to Phthalates and Risk of Childhood Obesity at age 12

Introduction: Early life exposure to endocrine disrupting chemicals, including phthalates, has been hypothesized to increase risk of obesity, but few studies have examined the association of prenatal phthalate exposure and later body mass index (BMI). Methods: Using data from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) longitudinal birth cohort study, we examined the association of 11 phthalate metabolites in maternal urine from two time points during pregnancy (~13 and 26 weeks gestation) with BMI, waist circumference, and percent body fat measured at 12 years of age (N=302 children). Age- and sex-specific BMI Z-scores were calculated from WHO Child Growth Standards and obesity was defined as BMI Z-score ≥95th percentile. Phthalate metabolites were examined individually and as the sum of low molecular weight (ƩLMW), high molecular weight (ƩHMW), and 2-diethylhexyl phthalate (ƩDEHP) metabolites. The mean of the two pregnancy metabolite concentrations was log10-transformed for analysis. Results: Each 10-fold increase in prenatal ƩLMW phthalates was associated with increases in BMI z-score (β= 0.3, 95% confidence interval (CI): 0.1, 0.5), waist circumference (β=5.8 cm, 95% CI: 2.8, 8.7), and percent body fat (β=4.1 %, 95% CI: 1.5, 6.7) and increased odds of obesity (OR=2.3, 95% CI 1.3, 4.1) at age 12. Similar results were seen with monoethyl phthalate, the dominant LMW metabolite. No statistically significant associations were seen with ƩHMW or ƩDEHP or any other individual metabolites. We did not observe interaction by sex, so results are presented for boys and girls together. Models controlled for maternal factors, including prenatal BMI, education, and income, and child factors at age 12, including puberty status, soda and fast food consumption, and time watching television. Conclusions: We found evidence that in utero exposure to LMW phthalates are associated with increased BMI and obesity at age 12 years.