Impact of Disproportionate Air Pollution and Heat Exposure on Pregnancy

Climate change, environmental pollution and ecological degradation have been linked to undeniable and debilitating consequences on human health outcomes. The World Health Organization (WHO) reports that climate change is expected to cause approximately 250,000 additional deaths every year between 2030 and 2050. This assessment includes direct mortalities as well as indirect deaths, such as from higher rates of infectious diseases, malnutrition, malaria, diarrhea and other climate-sensitive effects like heat stress.

In a similar vein, outdoor air pollution is one of the most significant causes of human mortality, leading to 4.2 million premature deaths per year. Studies, including the Air Quality Life Index (AQLI), show that sustained exposure to an additional 10 micrograms per cubic meter of particulate matter reduces life expectancy by 0.64 years. Disproportionate air pollution exposure is one consequence of pre-existing social inequalities and often particularly affects the physical and mental health of people with more acute vulnerabilities. Its effects are notably serious for pregnant women, especially of color, who already face high health inequities.

Several epidemiological studies have linked maternal exposure to air pollution and high heat to adverse pregnancy outcomes, including premature, underweight, or stillborn births. A review of 68 such studies by medical researchers Bekkar, Pacheco, Basu and DeNicola (2020) found strong evidence on increased risk of adverse pregnancy outcomes due to prenatal air pollution and heat exposure in the United States.

The analysis finds that exposure to PM_2.5 or ozone increased risk of preterm birth by an average of 11.5% and of low birth weight by 19%. Exposure to ozone escalates risk of preterm birth by about 6% and of low birth weight by about 6 – 13%. The review notes worse outcomes for certain racial groups (notably Black women). The authors also link extreme ambient temperatures to increased risk of preterm birth. Again, Black mothers were found to be among the highest at-risk groups, followed by Asian mothers and young mothers.

Black women are three times more likely to die from a pregnancy-related cause than White women in the U.S., and the study documents this higher vulnerability occurring, in part, due to environmental pollution. Multiple other factors contribute to this disparity, such as differences in healthcare access and quality, and conditions perpetuated by structural racism. Other at-risk subgroups identified include younger and older mothers, those with less educational level, and those lacking early prenatal care. Other similar studies have noted associations between lower socioeconomic status, place of residence, and proximity to roadways with increased risk of pregnancy-related mortality.

The review encompasses nearly 32 million births in the U.S. Even though a meta-analysis could not be performed due to heterogeneity (variable characteristics) of the study populations and of the heat and pollutant exposures, the large size of literature scoped by the authors makes the paper one of the most comprehensive literature reviews of its kind. A more recent review published in Current Environmental Health Reports (Ha, 2022) corroborates Bekkar et. al.’s findings, and the latest IPCC report by Working Group II also reports on the linkages between exposure to environmental pollution and pregnancy.

The authors shed light on the higher risk of obstetrical complications faced by pregnant women of color in the U.S. — clearly a significant issue. In the broader scheme of environmental health policy, racial and gender disparities in bearing climate- and pollution-caused health problems can lack adequate documentation, and they are without a doubt a considerably under-addressed policy problem. The authors suggest that the medical community, especially women’s health clinicians, incorporate contemporary findings on climate-related vulnerabilities into their plans of care and their risk communication. This would also require collecting better female health data and filling in the health-related gender data gap. On a macroscopic scale, climate change mitigation and air quality improvements as well as better integration of climate and air pollution policies can yield considerable human health improvements — just one more reason for governments to pursue cleaner air and a more habitable environment.

Source: McMichael, Rosalie & Hales (2006)