Environmental phthalate exposure is associated with increased odds of preterm birth

Abstract

Background: Preterm birth is a leading cause of neonatal mortality with a variety of associated risk factors. Environmental exposures represent an important but understudied set of potential contributors. Phthalate diesters are used extensively in a variety of consumer products worldwide. Consequently, exposure in pregnant women is highly prevalent. In this study we investigate the relationship between phthalate exposure during pregnancy and preterm birth. Methods: From 2006-2008 women planning to deliver at the Brigham and Women’s Hospital in Boston were prospectively enrolled in an observational cohort study. Each provided demographic data, samples, and information about birth outcomes. Within this group we selected 132 cases of preterm birth and 350 randomly assigned controls, and analyzed urine samples from three time points during pregnancy for levels of phthalate metabolites. We hypothesized there is a relationship between phthalate exposure and preterm birth. Results: Geometric means of the di-2-ethylhexyl phthalate (DEHP) metabolites mono-(2-ethyl)-hexyl phthalate (MEHP) and mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), as well as mono-n-butyl phthalate (MBP) and mono-(3-carboxypropyl) phthalate (MCPP) were significantly higher in cases compared to controls. In adjusted models, MEHP, MECPP, and ?DEHP metabolites were associated with significantly increased odds of preterm birth. When spontaneous preterm births were examined alone, MEHP, mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), MECPP, ?DEHP, MBP, and MCPP metabolite levels were all associated with significantly elevated odds of delivery. Conclusions: These results are consistent with evidence from toxicological and exploratory human studies and support a relationship between phthalate exposure and increased risk of preterm birth. As phthalate exposure can be avoided, steps should be taken to decrease maternal exposure to phthalates during pregnancy.