Air pollution exposure in pre-pregnancy months linked to higher obesity risk in kids: Study

In a study of 5,800 mother-child pairs, pre-pregnancy air pollution exposure was linked to higher BMI and obesity risks in children up to age 2.

Increased exposure to air pollution in the months prior to pregnancy is associated with higher body mass index (BMI) and obesity risk factors in children up to two years after birth, a study involving over 5,800 mother-child pairs from China has shown.

The study, published in the journal Environmental Research, found that an increase in PM2.5 levels by 16.2 micrograms per cubic metre during preconception -- three months prior to pregnancy -- was linked to a rise of 0.078 in child BMIZ at age two.

A BMIZ, or body mass index z-score, is used to compare a child's BMI with that of peers of the same age and sex.

Risks of pollution during preconception

Researchers from the US and China recruited the mother-child pairs from maternity clinics in Shanghai to understand how exposure to PM2.5, PM10 and nitrous oxide pollution during preconception impacted children's growth in the first two years of life.

The team also found that an increase in PM10 pollution by 21.1 micrograms per cubic metre was associated with an increase of 0.093 in the child's BMI at age two.

A commuter rides their bike during a foggy winter cold morning amid rising air pollution. (Sunil Ghosh / Hindustan Times)

Further, from the age of six months onward, children exposed to higher levels of pollution during preconception were found to have higher weight, BMI and BMIZ growth rates. Air pollution exposure at the participants' home addresses was estimated using satellite data, pollutant modelling and meteorological factors.

"The magnitude is small, but because air pollution is widespread and everybody is exposed, the risk of exposure on children's obesity may be substantial and may start before their mothers' pregnancy," senior author Zhanghua Chen, an assistant professor of population and public health sciences at the Keck School of Medicine, University of Southern California, US, said.

Exposure of pregnant women to air pollution has been linked to negative effects on children's health, such as respiratory conditions and a higher risk for chronic ones, including obesity and heart disease.

However, few studies have looked at preconception -- environmental exposures during this period can affect the health of sperm and eggs, which are in their final stages of growth, the researchers said.

"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," first author Jiawen Liao, a postdoctoral research associate in population and public health sciences at the Keck School of Medicine.

While the study is observational and could not establish cause-and-effect links, the researchers suggested measures to lower potential harm, including wearing a mask, using air purifiers and staying indoors as much as possible when outdoor air quality is poor.