Exposure to wildfire smoke and heat stress can have detrimental effects on birth outcomes for women, particularly in climate-vulnerable neighborhoods. A recent study led by USC postdoctoral researcher Roxana Khalili, Ph.D., sheds light on this issue. The study, published in Environmental Science & Technology, is among the first to demonstrate that living in areas more susceptible to climate-related exposures can significantly impact the effects of heat stress on adverse birth outcomes, even among women exposed to these conditions in the month before pregnancy.
“We already know that poor air quality can lead to adverse health outcomes, especially for pregnant women and fetuses who are particularly vulnerable,” explained Khalili, who is a researcher at USC’s Keck School of Medicine. “Our understanding of the specific effects of wildfire smoke during pregnancy has been limited, and even less is known about the impact of these hazards around or just before conception.”
Khalili collaborated with Rima Habre, the director of USC’s CLIMA Center, to investigate the connections between exposure to wildfire smoke and heat stress on infant health. They utilized data from the MADRES cohort, an ongoing study of pregnant women in Los Angeles.
The research team analyzed 713 births among MADRES participants from 2016 to 2020. They leveraged data from CalFIRE to identify the location, size, and duration of wildland fires in southern California during the study period. By using the NOAA hazard mapping system, they calculated the smoke density from each fire and estimated the particle pollution that women in the cohort were exposed to based on their daily residential location histories.
Heat stress is another risk factor for pregnant women and fetuses, as pregnancy can hinder a woman’s ability to regulate body temperature. The researchers measured heat stress exposures by analyzing meteorological data on temperature, humidity, wind speed, and sun exposure. They also identified climate-vulnerable neighborhoods using geospatial tools like the California Urban Heat Island Index and the US Climate Vulnerability Index.
The study revealed that increased exposure to wildfire smoke and heat stress in the month before conception and the first trimester of pregnancy was associated with higher odds of having a small-for-gestational-age (SGA) baby. SGA infants are at greater risk of health complications, both immediate and long-term. Additionally, exposure to moderate smoke-density days in the first trimester was linked to a higher likelihood of having a low-birth-weight baby.
The findings underscore the importance of understanding the impact of climate-related hazards on pregnant women and developing interventions to mitigate these risks. As climate change continues to exacerbate wildfire seasons and heatwaves, proactive measures are essential to protect maternal and infant health.
The study’s lead author, Khalili, emphasized the need for comprehensive research and interventions to address the cumulative impacts of climate-related exposures on vulnerable communities. By focusing on community resilience and implementing targeted strategies, healthcare providers and policymakers can better safeguard the health of pregnant women and their infants in the face of escalating climate challenges.
