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John D. Meeker,¹ Howard Hu,¹ David E. Cantonwine,¹ Hector Lamadrid-Figueroa,² Antonia M. Calafat,³ Adrienne S. Ettinger,^1,4 Mauricio Hernandez-Avila,⁵ Rita Loch-Caruso,¹ and Martha María Téllez-Rojo²

¹Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan, USA; ²Division of Statistics, Center for Evaluation Research and Surveys, National Institute of Public Health, Cuernavaca, Mexico; ³Centers for Disease and Control and Prevention, Atlanta, Georgia, USA; ⁴Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA; ⁵Ministry of Health, Mexico City, Mexico

Abstract
Background: Rates of preterm birth have been rising over the past several decades. Factors contributing to this trend remain largely unclear, and exposure to environmental contaminants may play a role.

Objective: We investigated the relationship between phthalate exposure and preterm birth.

Methods: Within a large Mexican birth cohort study, we compared third-trimester urinary phthalate metabolite concentrations in 30 women who delivered preterm (< 37 weeks of gestation) with those of 30 controls (≥ 37 weeks of gestation) .

Results: Concentrations of most of the metabolites were similar to those reported among U.S. females, although in the present study mono-n-butyl phthalate (MBP) concentrations were higher and monobenzyl phthalate (MBzP) concentrations lower. In a crude comparison before correcting for urinary dilution, geometric mean urinary concentrations were higher for the phthalate metabolites MBP, MBzP, mono(3-carboxylpropyl) phthalate, and four metabolites of di(2-ethylhexyl) phthalate among women who subsequently delivered preterm. These differences remained, but were somewhat lessened, after correction by specific gravity or creatinine. In multivariate logistic regression analysis adjusted for potential confounders, elevated odds of having phthalate metabolite concentrations above the median level were found.

Conclusions: We found that phthalate exposure is prevalent among this group of pregnant women in Mexico and that some phthalates may be associated with preterm birth.

Key words: case–control, environment, epidemiology, exposure, pregnancy, prematurity. Environ Health Perspect 117:1587–1592 (2009) . doi:10.1289/ehp.0800522 available via http://dx.doi.org/ [Online 16 June 2009]

Address correspondence to J. Meeker, Department of Environmental Health Sciences, University of Michigan School of Public Health, 6635 SPH Tower, 109 S. Observatory St., Ann Arbor, MI 48109 USA. Telephone: (734) 764-7184. Fax: (734) 936-7283. E-mail: meekerj@umich.edu

We thank M. Silva, E. Samandar, J. Preau, and T. Jia [Centers for Disease Control and Prevention (CDC) ] for technical assistance in measuring the concentrations of phthalate metabolites.

This work was supported by R01 ES 007821, P42 ES 05947 Project 1, and a pilot project grant from the Department of Environmental Health Sciences, University of Michigan School of Public Health.

The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the CDC.

The authors declare they have no competing financial interests.

Received 26 December 2008 ; accepted 16 June 2009.