Environmental Health Perspectives is an Open Access journal published by the National Institute of Environmental Health Sciences. Environmental Health Perspectives is an Open Access journal published by the National Institute of Environmental Health Sciences.

Prematurity is a leading cause of neonatal mortality and can lead to an array of adverse health effects in the lives of those who survive. The contribution of environmental exposures to preterm birth is understudied; however, identification of potential contributing factors offers significant hope for combating preterm birth for several reasons: (1) pregnant women are unintentionally exposed to many chemicals throughout gestation, some of which have demonstrated reproductive toxicities¹; (2) increased exposure to some chemicals over past decades correlates strongly with increased rates of preterm birth, which may be the result of various confounders but may also indicate a real association; and (3) exposure to environmental contaminants may be largely modifiable, opportune for interventions at the individual, clinical, and population levels.

A peer-reviewed open access journal published by the National Institute of Environmental Health Sciences

Background: Phthalate exposure occurs readily in the environment and has been associated with an array of health end points, including adverse birth outcomes. Some of these may be mediated by oxidative stress, a proposed mechanism for phthalate action. Objectives: In the present study, we explored the associations between phthalate metabolites and biomarkers of oxidative stress measured in urine samples from multiple time points during pregnancy. Methods: Women were participants in a nested case–control study of preterm birth (n = 130 cases, n = 352 controls). Each was recruited early in pregnancy and followed until delivery, providing urine samples at up to four visits. Nine phthalate metabolites were measured to assess exposure, and 8-hydroxydeoxyguanosine and 8-isoprostane were also measured in urine as markers of oxidative stress. Associations were assessed using linear mixed models to account for intraindividual correlation, with inverse selection probability weightings based on case status to allow for greater generalizability. Results: Interquartile range increases in phthalate metabolites were associated with significantly higher concentrations of both biomarkers. Estimated differences were greater in association with monobenzyl phthalate (MBzP), mono-n-butyl phthalate (MBP), and monoisobutyl phthalate (MiBP), compared with di(2-ethylhexyl) phthalate (DEHP) metabolites. Conclusions: Urinary phthalate metabolites were associated with increased oxidative stress biomarkers in our study population of pregnant women. These relationships may be particularly relevant to the study of birth outcomes linked to phthalate exposure. Although replication is necessary in other populations, these results may also be of great importance for a range of other health outcomes associated with phthalates. Citation: Ferguson KK, McElrath TF, Chen YH, Mukherjee B, Meeker JD. 2015. Urinary phthalate metabolites and biomarkers of oxidative stress in pregnant women: a repeated measures analysis. Environ Health Perspect 123:210–216; http://dx.doi.org/10.1289/ehp.1307996