A new study published in Environmental Research  revealed that exposure to air pollution in the three months preceding pregnancy may raise the risk of obesity in children up to two years old. Researchers evaluated data from over 5,000 women and their children and discovered a relationship between preconception pollution exposure and greater BMI and other risk factors. 

Previous studies have demonstrated that air pollution during pregnancy can cause a variety of health issues in children, including respiratory disorders and an increased risk of chronic conditions such as obesity and heart disease. However, this study emphasises the preconception period as an important window for exposure.

Jiawen Liao, PhD, a postdoctoral research associate at the Keck School of Medicine and the study's first author, emphasised the significance of this finding. "These findings imply that the three months before conception are important, and that people who plan to bear children should consider taking measures to lower their air pollution exposure to reduce their children's risk for obesity," according to Liao. 

Researchers from the Keck School of Medicine at USC, Duke University, and Fudan University in Shanghai conducted one of the largest studies on preconception environmental exposures, examining 5,834 mother-child pairings. The participants were from 28 maternity clinics in Shanghai. 

Weili Yan, PhD, and Guoying Huang, PhD, from Fudan University's Children's Hospital, led the study team that used advanced machine learning algorithms to estimate air pollution exposure. Duke University's Jim Zhang, PhD, helped build models that used satellite data, pollutant simulations, and meteorological factors to estimate daily pollution levels at participants' homes. They focused their efforts on tiny particulate matter (PM2.5 and PM10) and NO2, a gas primarily produced by cars. 

We analysed the children's medical records every three months after birth, until they reached the age of two. Greater preconception exposure to PM2.5, PM10, and NO2 was associated with a greater BMI and BMIZ (a standardised BMI score adjusted for age and sex). 

The study found that children of mothers with high preconception exposure (75th percentile) had a 0.078 increase in BMIZ at age two, while those with low exposure (25th percentile) had a 0.093 kg/m² increase in BMI at the same age. Furthermore, children exposed to higher levels of pollution prior to conception have faster growth rates in weight, BMI, and BMIZ from six months onwards. 

Zhanghua Chen, PhD, the senior author of the paper, emphasised the prevalence of air pollution. "The magnitude is small, but because air pollution is widespread and everybody is exposed, the risk of air pollution exposure on children's obesity risk may be substantial and may start before their mothers' pregnancy," according to Chen. 

Although the study is observational and does not prove a direct cause-and-effect relationship, experts advise caution. People planning a pregnancy can decrease their exposure to air pollution by staying indoors or wearing masks on high-pollution days, as well as using air purifiers at home. Making lifestyle modifications to reduce pollution exposure may also be effective in lowering risks. 

Researchers at the Keck School of Medicine are developing a new study in Southern California to assess preconception air pollution exposure and test interventions that use home air purifiers to lower health risks.