Exposure to common air pollutants during the earliest weeks of pregnancy could increase the risk of experiencing persistent depressive symptoms throughout pregnancy, according to new research.
The study, led by researchers at Washington University in St. Louis and the University of Southern California, found that women exposed to higher levels of pollutants such as nitrogen dioxide and PM2.5 during the first six weeks of pregnancy were more likely to report ongoing symptoms of depression.
Depression affects an estimated one in five women during pregnancy and has been linked to complications including preterm birth, postpartum depression and developmental problems in children. While previous research has suggested a link between air pollution and depression, this study is one of the first to examine how depressive symptoms change over the course of pregnancy.
Researchers analysed data from 542 women taking part in the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) study, a long-running project involving predominantly low-income Hispanic and Latina women in Los Angeles. Participants completed depression questionnaires during each trimester, allowing researchers to identify patterns in mental health over time.
The team found four distinct symptom trajectories. Around 43% of women experienced consistently low levels of depressive symptoms throughout pregnancy, while 35% saw symptoms ease over time. However, nearly 15% experienced persistently moderate symptoms and 7.4% reported consistently high levels of depression, with symptoms peaking around the middle of pregnancy.
Women with higher exposure to several common air pollutants during early pregnancy were significantly more likely to belong to the highest-risk group. The strongest link was seen with nitrogen dioxide, a pollutant largely produced by road traffic. Women with the highest exposure during the first six weeks of pregnancy were nearly four times more likely to experience persistent, clinically relevant depressive symptoms than those with lower exposure.
The researchers believe early pregnancy may represent a particularly vulnerable period. During the first few weeks, the body undergoes major hormonal and biological changes to support the developing baby. Previous research suggests air pollution can trigger inflammation, oxidative stress and changes to the body’s stress-response system – processes that have all been associated with depression.
Tracy Bastain, a professor of public health, who co-authored the study, said: ‘It is always a challenge to tease out all of the possible contributing factors that may account for higher trajectories of depression during pregnancy. However, the associations we observed between air pollution exposure and depressive symptom trajectories remained consistent after accounting for multiple potential confounding factors.’
The full research can be read here.
Photo: Amr Taha™
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