Commute Length and Preterm Birth: Results From the UCLA Environment and Pregnancy Outcomes Study

Abstract

ISEE-445 Objective: We used data from a 2003 nested case-control study to investigate the influence of commuting length on adverse birth outcomes. Material and Methods: We surveyed 2543 women in Los Angeles County, California (half of whom gave birth to a low weight or preterm infant) 4 to 6 months postdelivery to collect information on pregnancy risk factors not recorded on birth certificates and time-activity patterns. We calculated average commute times (minutes per day) for each woman who worked outside the home during pregnancy, weighting the commuting length reported for each home by the time spent in each home for women who moved. Results: Fifty-three percent of surveyed women (n = 1345) worked outside the home during pregnancy. Approximately 81% reported commuting by car, 13% by bus, 5% by walking, and 1% by metro. We observed a 27% increase in odds of preterm birth for women with pregnancy-average commute times of 30+ minutes compared with those with <30 minutes (OR = 1.27, 95% CI = 0.99–1.62) and a 35% increase for women commuting 60+ minutes (OR = 1.35, 95% CI = 0.99–1.85), after adjusting for maternal age, race/ethnicity, and education, parity, and season. Additional adjustment for covariates collected during our survey (active and passive smoking, alcohol consumption, and marital status) did not change these estimates appreciably. We did not observe associations between term LBW and commute length, but statistical power to examine this outcome was limited. Conclusions: We observed an increase in odds of preterm birth for women who commuted 30+ minutes to work, suggesting in vehicle exposures to motor vehicle pollutants during pregnancy may be an exposure route to consider in future studies. In subsequent analyses, we plan to examine changes in our results when adjusting for stress and occupation and when stratifying on vehicle model year since older vehicles with aging or malfunctioning emission control systems emit more pollutants.