Air pollution, ambient temperature, green space and preterm birth

Preterm birth is the leading cause of global child mortality, and survivors are at increased risk of multiple morbidities that can continue into adulthood. Recent studies have suggested that maternal exposure to air pollution and high and low ambient temperatures may increase the risk of preterm birth, whereas proximity to green space may decrease it. This review summarizes these findings and suggests avenues for further research.Particulate matter may be associated with an increased risk of preterm birth, but the magnitude of the effect remains unclear. Heat and cold likely increase the risk of preterm birth, with stronger evidence for heat. The first and third trimesters may be sensitive periods for exposure to both temperature and particulate matter, but the underlying biological mechanisms are incompletely understood. Context-appropriate green space can substantially reduce particulate matter levels and mitigate urban heat islands.In a warming, urbanizing world, exposure to unusual temperatures and elevated particulate matter levels represent an increasing risk for pregnant women. Green infrastructure might help mitigate this risk, but further research is needed to confirm its effects in complex urban environments and evaluate the contribution of both indoor and outdoor particulate matter and air temperature to personal exposure and preterm birth.