Ambient Air Pollution and Stillbirths Risk in Sydney, Australia.

We aimed to determine the associations between ambient air pollution, specifically particulate matter less than or equal to 10 microns and 2.5 microns (PM and PM respectively) and ozone (O), and stillbirths. We analysed all singleton births between 20-42 weeks gestation in metropolitan Sydney, Australia, from 1997 to 2012. We implemented logistic regression to assess the associations between air pollutants and stillbirth for each trimester and for the entire pregnancy. Over the study period, there were 967,694 live births and 4287 stillbirths. Mean levels of PM, PM and O for the entire pregnancy were 17.9 µg/m, 7.1 µg/m and 3.2 ppb, respectively. Adjusted odds ratios were generally greater than unity for associations between PM and stillbirths, but none were statistically significant. There were no significant associations between O and stillbirths. There was potential effect modification of the PM and O association by maternal age. We did not find consistent evidence of associations between PM and O and stillbirths in Sydney, Australia. More high quality birth cohort studies are required to clarify associations between air pollution and stillbirths.