A study indicates that prenatal exposure to several ambient air pollutants during pregnancy may impair infant growth, which could increase the risk of childhood obesity.

Exposure, to, air, pollution, during, pregnancy, may, increase, the, risk, of, obesity, in, babies

We know that air pollution has consequences on the health of individuals, pregnant women being particularly vulnerable. Indeed, exposure during pregnancy presents a risk for fetal health and for the child, since several studies have highlighted the fact that it is associated with deleterious impacts such as pre-eclampsia in pregnant women (hypertension associated with the presence of proteins in the urine), a reduced birth weight in the child and even a degraded functioning of the lungs and neurodevelopmental disorders. A new study reveals an as-yet-unknown effect on the unborn child, which also involves its weight.

Researchers at the University of Colorado at Boulder say in a study published in the journal Environmental Health that pregnant women exposed to higher levels of air pollution during pregnancy have babies that grow abnormally fast in the first few months after birth. This puts them at risk for obesity and related diseases later in life. This study therefore suggests that poor air quality may be contributing at least in part to the obesity epidemic in some countries, particularly among disadvantaged populations that tend to live in places with greater exposure to toxic pollutants.

How is a large birth weight dangerous?

"Higher rates of obesity among certain groups in our society are not simply a byproduct of personal choices such as sedentary lifestyles and calories consumed and expended. It's more complicated. "This study and others suggest that obesity is a byproduct of the way we live. "This study and others suggest that they may also be related to environmental load. "Regarding one of the adverse effects of pollution during pregnancy, namely low birth weight babies, it has been shown that during the first year of life, these babies tend to catch up, and gain weight very quickly. But the opposite consequence is more complex and even dangerous.

Accelerated weight gain in early life can lead to diabetes, heart disease and weight problems in childhood, adolescence and adulthood. To take a closer look at the impact of certain pollutants on a baby's growth trajectory, researchers followed 123 mother-child pairs from the Mother's Milk Study, an ongoing study in Los Angeles. About one-third were of normal weight before pregnancy, one-third overweight, and one-third obese. They then used data from the U.S. Environmental Protection Agency's air quality system, which records air quality data via monitoring stations.

Greater weight gain in the following six months

The goal: to quantify their prenatal exposure to four classes of pollutants: fine particles such as PM2.5 and PM10 (inhalable particles from factories, cars and construction sites), nitrogen dioxide (an odorless gas emitted by cars and power plants) and ozone. When the babies were born, they were medically monitored for several weeks to measure their weight, height, but also their body fat. "We found that greater prenatal exposure to air pollution was associated with greater changes in weight and adiposity, or body fat, in the first six months of life. ", the researchers note.

But how can inhalation of pollutants impact infant growth? The researchers hypothesize that pollutants can inflame the mother's lungs and cause systemic organ inflammation, affecting metabolic processes, such as insulin sensitivity, which in turn can influence fetal development. Pollutants have also been shown to impact gene expression in infants, with potential lifelong and even multigenerational effects. However, scientists believe that a larger study is needed to confirm that these findings apply to other populations.

 In the meantime, they recommend that pregnant women take extra precautions to minimize their exposure to pollution with several tips: close windows on days with high ozone concentrations, do not exercise outdoors during periods of high pollution and avoid activities along busy roads. Note that in France, women are also concerned since an Inserm study published in 2018 revealed that prenatal exposures to air pollutants, at levels commonly found in Europe, could have adverse effects on the health of the unborn child, including epigenetic changes in the placenta.