New research has revealed that air pollution exposure in the three months leading up to conception may contribute to higher body mass index (BMI) and an increased risk of obesity-related health problems in children up to two years old. The findings, published in Environmental Research, are based on a study of over 5,000 mother-child pairs and were supported by the National Institute of Environmental Health Sciences.
While previous studies have established links between air pollution during pregnancy and a range of health issues in children, including respiratory problems and a heightened risk of obesity and heart disease, this study is one of the first to focus on the preconception period—the three months prior to pregnancy. During this time, sperm and eggs undergo final stages of development, making environmental exposures during this period particularly impactful.
Researchers from the Keck School of Medicine at USC, Duke University, and Fudan University in Shanghai, China, studied 5,834 mother-child pairs recruited from maternity clinics in Shanghai. They found that exposure to pollutants such as PM2.5, PM10, and NO2 in the months leading up to pregnancy was associated with higher BMI or BMI-for-age z-scores (BMIZ) in children.
“The three months before conception are important, and individuals planning to have children should consider reducing their exposure to air pollution to help lower their children’s risk of obesity,” said Dr. Jiawen Liao, the study’s postdoctoral researcher.
The study, led by Weili Yan, PhD, and Guoying Huang, PhD, of Fudan University’s Children’s Hospital, had the advantage of collecting data prior to conception. Researchers used advanced machine learning models, along with satellite data, pollutant simulations, and meteorological factors, to estimate daily pollution exposure at each participant’s home. Specifically, they measured PM2.5 and PM10—types of fine particulate matter—and NO2, which is primarily emitted by vehicles.
Following birth, the team tracked the children’s weight and height at three-month intervals until age two, allowing for a comprehensive analysis of growth rates and BMI.
When comparing children with relatively low exposure to pollution (the 25th percentile of the cohort) with those exposed to higher levels (the 75th percentile), the study found that higher exposure to PM2.5 during the preconception period was linked to a 0.078 increase in BMIZ at age two. Similarly, higher exposure to PM10 was associated with a 0.093 kg/m² increase in BMI at the same age. From six months onward, children exposed to higher pollution levels during the preconception period showed faster growth in weight, BMI, and BMIZ.
“The effects are small, but given the widespread nature of air pollution and the fact that everyone is exposed, the overall risk to children’s obesity could be significant and may begin before their mothers even conceive,” said Dr. Zhanghua Chen, senior author and assistant professor at the Keck School of Medicine.
Though the study is observational, the researchers suggest that individuals can take action now to reduce the potential harm of air pollution exposure. These actions include wearing masks or staying indoors when air quality is poor and using air purifiers inside. While the study focused on mothers, men planning to conceive may also benefit from similar precautions.
The researchers are also planning follow-up studies to monitor preconception air pollution exposure in Southern California and are testing interventions such as indoor air purifiers to mitigate risks for heart and metabolic issues in the general population.
While more research is needed to determine the direct link between preconception air pollution exposure and childhood obesity, the study highlights the importance of environmental factors during this critical period before pregnancy. It also underscores the need for public health strategies aimed at reducing air pollution exposure for future generations.
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