Climate change is known to adversely affect women's health and birth outcomes. A systematic review of the literature was undertaken to determine the associations between exposure to fine particulate matter less than 2.5 micrometers in diameter, ozone, and heat and outcomes including preterm birth, low birth weight, and stillbirth in the U.S. population.

A total of 68 studies met the study criteria: 58 were on air pollutants and 10 were on heat. Overall, 32,798,152 births were analyzed.

Of the studies on air pollution, 48 showed a significant association between exposure to air pollutants and adverse birth outcomes. Of the heat studies, nine showed a significant association between exposure to heat during pregnancy and adverse birth outcomes.

Maternal exposure to fine particulate matter and/or ozone was associated with increased risk of preterm birth in 19 of 24 studies, low birth weight in 25 of 29 studies, and stillbirth in four of five studies.

The risk of preterm birth was higher for Black women and for women who have asthma. The associations between exposure to air pollution and heat and adverse birth outcomes were found across the continental United States.

The authors note that results can vary based on differences in the exposure measurement methods and population demographics of a study. Moreover, direct comparison of data, even within a given study, may be complicated owing to different study designs. They advise health providers to discuss the emerging data on environmental exposures with patients and to integrate them into patients' care plans.