Exposure to air pollution during pregnancy is associated with growth delays

Exposure to air pollution by pregnant women has previously been linked to lower birth weight and respiratory and neurodevelopmental problems in children. Now, a new study by the Barcelona Institute for Global Health (ISGlobal) has found an association betwen exposure to air pollution during pregnancy and delays in physical growth in the early years after birth.

The research involved more than 1,700 mother-child pairs in Spain. In all of them, the scientists:

• Estimated the exposure to nitrogen dioxide (NO₂) and fine particulate matter (PM_2.5) — two of the most common traffic-related air pollutants in cities — during the first trimester of pregnancy.
• Analysed the evolution of the children’s body mass index (BMI) from birth to age four years. Height and weight were also measured at four years of age.

The results showed that greater exposure to particulate matter during the first trimester of pregnancy was associated with a higher risk of lower weight and body mass index at four years of age. Results for NO₂ exposure were similar but did not reach statistical significance.

Although the biological mechanisms underpinning the adverse effects of air pollution on childhood growth “remain unclear”, the researchers’ hypotheses would include oxidative stress and inflammation, interference with thyroid hormones, and an increased risk of respiratory disease and other health problems as possible triggers that could delay growth.