Exposure to air pollutants during pregnancy, specifically nitrogen dioxide (NO2) and inhalable particulate matter (PM10), is associated with a significantly higher risk of developing postpartum depression, a new study reveals. The risk of depression persists for at least three years following childbirth, according to research published in the Science of the Total Environment journal.
Dr. Tracy Bastain, an associate professor of clinical population and public health sciences at the Keck School of Medicine of USC and the senior author of the study, highlighted the study’s novel aspect. “What sets this research apart is its examination of depressive symptoms extending beyond the first year postpartum, demonstrating the enduring impact of prenatal air pollution on depression up to three years after childbirth,” Bastain said.
NO2, a byproduct of fossil fuel combustion in vehicles and power plants, and PM10, which includes particles from dust, pollen, factories, and wildfires, have been linked to various health issues, such as asthma, cardiovascular disease, and stroke. This study adds postpartum depression to the list of potential health effects related to air pollution.
The longitudinal study tracked 361 mothers from the start of their pregnancies through three years postpartum. Researchers assessed depressive symptoms at one, two, and three years after delivery and compared these with weekly air pollution levels recorded near their homes during pregnancy. The study found a significant correlation between elevated pollution levels and increased depressive symptoms.
Women exposed to higher levels of NO2 between weeks 13 and 29 of pregnancy were nearly four times more likely to experience postpartum depression over the following three years. Similarly, higher exposure to PM10 between weeks 12 and 28 was associated with nearly four times the risk of postpartum depression. In the study cohort, 17.8% of women exhibited depressive symptoms one year postpartum, 17.5% after two years, and 13.4% after three years.
“Our findings reveal a higher incidence of clinically significant depression compared to recent CDC data,” Bastain noted. “This indicates that postpartum depression may be more widespread than current national prevalence estimates suggest.”
The study underscores the importance of ongoing mental health screening beyond the first year after childbirth and suggests that reducing air pollution exposure during the second trimester could mitigate depression risk.
The research was conducted by the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) Center for Environmental Health Disparities at the Keck School of Medicine, which monitors predominantly Hispanic/Latino families in Los Angeles. The team utilized the Center for Epidemiologic Studies-Depression (CES-D) scale to measure depressive symptoms and cross-referenced residential addresses with local air quality data to calculate pollution exposure.
The study revealed that higher NO2 exposure during specific pregnancy weeks increased the risk of postpartum depression by a factor of 3.86, while higher PM10 exposure increased the risk by 3.88. Exposure to PM2.5 and ozone did not show a significant impact on postpartum depression risk.
Bastain emphasized the importance of minimizing exposure to air pollution during pregnancy and suggested practical measures such as avoiding outdoor exercise during high pollution periods and staying indoors during peak pollution hours.
Looking ahead, Bastain and her team at the MADRES Center plan to further investigate the long-term effects of air pollution and other environmental exposures on maternal and child health, with a focus on understanding the underlying biological mechanisms.
“Our goal is to advance this research to better safeguard the health of mothers and children over the long term,” Bastain concluded.
