A systematic review which included 68 studies and more than 32 million births in the United States explored whether women exposed to particulates, ozone and heat were more likely to have a baby who was born prematurely, or small for dates.

Air pollution, damage to the ozone layer and rising temperatures are related to climate change and have been recognised by the World Health Organisation as hazardous to human health.

The review found that exposure to particulates or ozone increased the risk of premature birth and of low birth weight, and heat exposure was also associated with adverse birth outcomes. The women most at risk were those who were asthmatic or who came from minority groups, especially black mothers. A positive association between the hazards studied and compromised births was found in all geographical areas of the US.

The authors speculate as to why exposure to particulates, heat and ozone may lead to adverse birth outcomes. They suggest that inhaling particulates may trigger inflammation in pregnant women, increase the stickiness of the mother’s blood and thereby reduce perfusion of the placenta. It may have toxic effects on the unborn baby, causing altered gene expression. Heat exposure may lead to dehydration and inefficient thermoregulation, which may trigger premature labour. Black mothers may be at greater risk because they are more likely to live in heavily polluted urban areas and more likely to suffer from chronic stress in their lives; stress increases all other risks.

The authors conclude that exposure to certain aspects of the environment exacerbated by climate change has a strong negative association with birth outcomes. This finding adds to the pressure to find urgent solutions to climate change.

---

READ MORE: Bekkar, B. et al. (2020) Association of air pollution and heat exposure with preterm birth, low birth weight, and stillbirth in the US: A systematic review. JAMA Network, OPEN. Doi:10.1001/jamanetworkopen.2020.8243