Date of Award

January 2013

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Yawei Zhang



Background: Early studies have inconsistently linked ambient air pollutant PM10 exposure during pregnancy to the risk of preterm birth. However, majority of early studies were based on registry data which could result in misclassification of exposure due to the lack of detailed home and work addresses, as well as failed to collect information on potential confounders. China has the world's most polluted cities and suffers the second largest burden of preterm births. Very few studies, however, have been conducted in China to investigate the association between PM10 exposure and preterm birth. Building upon a birth cohort study conducted in Lanzhou, China, we investigated the hypothesis that high level exposure to PM during pregnancy increases the risk of preterm birth.

Methods: A total of 2,902 singleton live births without birth defects delivered at the Gansu Provincial Maternity and Child Care Hospital in 2009-2011 were included in the study. Air pollutant data of 24-hour average particulate matter with an aerodynamic diameter less than 10 um (PM10) was collected from four monitoring stations. Individual exposure levels of PM10 were assigned based on home and work addresses to air monitoring stations using inverse-distance weighting approach. Unconditional logistic regression model was used to calculate the Odds Ratio (OR) and 95% confidence interval (CI) to determine the association between preterm birth and PM10 exposure. We also explored the association after adjustment for the co-linearity by using Principal Component Analysis. Potential confounding factors such as maternal age, hypertension during pregnancy, season of conception, cesarean section, parity, active and passive smoking, and folic acid intake before pregnancy were included in the final model.

Results: Using the China National Ambient Air Quality Standards (NAAQS) Grade II level (0.15mg/m3), which is equivalent to the U.S. NAAQS level, as the reference, higher daily average concentration of PM10 during entire pregnancy was associated with an increased risk of preterm based on home address only (OR=2.15, 95%CI: 1.47-3.16). Similar association was also observed for the first trimester. Using the weighted concentration based on both home and work addresses, similar patterns were observed for the entire pregnancy (OR=1.96, 95%CI: 1.33-2.90) and the first trimester (OR=2.08, 95% CI: 1.22-3.52). Percentage of the days with daily average concentration of PM10 exceeding the standard was positively associated with the risk of preterm birth during the first trimester.

Conclusions: This study suggests that the ambient air pollutant PM10 has positive correlation with the preterm birth in Lanzhou, China.

Keywords: Preterm birth, PM10, China, Lanzhou, Birth cohort


This is an Open Access Thesis.