For pregnant women, exposure to fine particulate air pollution (PM2.5) was associated with altered immune responses that can lead to adverse birth outcomes, according to a new study led by Harvard T.H. Chan School of Public Health. The study is the first to examine the relationship between PM2.5 and maternal and fetal health on a single-cell level and highlights the health risk of PM2.5 exposure for pregnant women.

The study is published in Science Advances.

"This study represents a substantial step forward in understanding the biological pathways through which PM2.5 exposure affects pregnancy, maternal health, and fetal development. Its advanced methodology represents a significant innovation for how we study immune responses to environmental exposures," said corresponding author Kari Nadeau, John Rock Professor of Climate and Population Studies and chair of the Department of Environmental Health.

Previous research has found associations between exposure to PM2.5 and maternal and child health complications including preeclampsia, low birth weight, and developmental delays in early childhood. To understand these associations on a cellular level, the researchers used air quality data collected by the Environmental Protection Agency to calculate study participants' average PM2.5 exposure. Participants were both non-pregnant women and 20-week pregnant women.

The researchers then used an innovative technology to understand how pollution modified the DNA of participants' individual cells. Within each cell they were able to map changes to histones, the proteins that help control the release of cytokines—proteins that help control inflammation in the body and that can affect pregnancy.

The study found that PM2.5 exposure can influence the histone profiles of pregnant women, disrupting the normal balance of cytokine genes and leading to increased inflammation in both women and fetuses. In pregnant women, this increase in inflammation can correspond with adverse pregnancy outcomes.

"Our findings highlight the importance of minimising air pollution exposure in pregnant women to protect maternal and fetal health," said co-author Youn Soo Jung, research associate in the Department of Environmental Health. "Policy interventions to improve air quality, as well as clinical guidelines to help pregnant women reduce their exposure to pollution, could have a direct impact on reducing pregnancy complications."