The air that women breathe up to three months before they become pregnant can have an effect on the future baby’s size. A study of more than 5,000 mothers and their subsequent children suggests that exposure to air pollution before pregnancy was linked to a higher body mass index for the child and obesity risk for up to two years after birth.
The findings were published in the journal Environmental Research.
Researchers from the Keck School of Medicine at University of Southern California, Duke University and Fudan University in Shanghai, China, studied more than 5,800 mother-child pairs from maternity clinics in Shanghai. They found that greater exposure to three kinds of air pollution — PM2.5, PM10 and nitrous dioxide — before pregnancy was associated with higher body mass index and higher values on the standardized score that compares the child’s BMI to others of the same age and sex.
In a news release, Keck noted that earlier research already linked air pollution during pregnancy to health problems like respiratory issues and greater risk of chronic disease, including obesity and heart problems. But less has been shown about the pre-conception period when environmental exposures might affect the health of sperm and eggs.
“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,” said Jiawen Liao, a postdoctoral research associate in population and public health sciences at Keck and first author of the study.
Measuring nasty air
The researchers created cutting-edge learning models to calculate air pollution exposure in the months leading up to becoming pregnant. Jim Zhang of Duke University led the time, which used satellite data, pollutant simulations and meteorological information to estimate the daily pollution exposures at each study participant’s home. They looked specifically at the two types of fine particulate matter and the nitrous dioxide, which typically comes from vehicle exhaust.
To compare that data to baby’s size, they used electronic medical records on weight and height, gathered every three months until the child turned 2. They then compared those in a low exposure group when it came to pollution (the 25th percentile of the group) to those with relatively high exposure (the 75th percentile).
Exposure to each of the pollutants was linked to higher weight from 6 months onward, they found.
“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,” said Zhanghua Chen, an assistant professor of population and public health sciences at Keck and the study’s senior author.
Risks for mother and child alike
Studies have long confirmed that air pollution exposure in pregnancy poses risks for mothers and their babies. The American Pregnancy Association notes that low birth weight is one of the most-suspected outcomes. It’s not known if there’s a point within pregnancy where harm from exposure to pollution is more likely.
Other research has linked air pollution to different harms. The Stockholm Environment Institute at University of York says close to 3 million babies are born prematurely because of air pollution.
A Harvard study found women who are exposed to high particulate-matter pollution during the third trimester of pregnancy were twice as apt to have a child with autism. The association recounting of the research noted that exposure in the first two trimesters didn’t confer the same likelihood.
Studies link exposure during the pregnancy to the child developing asthma, as well. And some believe that air pollution contributes to lower fertility rates in both men and women.
A 2023 study involving researchers at multiple universities linked high levels of pollution during pregnancy to a variety of outcomes, including high blood pressure for the mom, postpartum depression, placenta problems, infant mortality, lung and breathing problems. The research called for “comprehensive, global efforts” to reduce pollution and protect the health of those who are vulnerable.
Protection from pollution
The new study’s authors warned that the study is observational and more research is needed to confirm a link between preconception pollution exposure and childhood obesity risk. But they recommend that people take steps to minimize their exposure.
Among their suggestions are wearing a mask when outdoor air quality is poor, or instead staying inside. They also recommend using an air purifier indoors.
The suggestions include prospective fathers, as well.
University of Texas Southwestern Medical Center offers several tips for reducing exposure to air pollution during pregnancy. They are:
- Pay attention to air quality around you.
- Avoid being outside if air quality is poor.
- Stay away from tobacco smoke.
- Get educated and active.
The Keck release said the researchers at its medical school are planning a new study to look at pre-conception air pollution exposure in Southern California and are also testing whether indoor air purifiers reduce the risk of heart and metabolic problems among the general population.