Air Pollution Exposure While Pregnant Delays Offspring Growth

Serena Fossati, MD, PhD

Investigators found an association between exposure to air pollution during pregnancy and stunted physical growth in offspring in the early years after birth.

Serena Fossati, MD, PhD, and a team of investigators included mother-child pairs from the Spanish INMA birth cohort to understand the association between outdoor air pollutants exposure in the first trimester of pregnancy and growth and cardio-metabolic risk at 4 years of age. The findings suggested that prenatal exposure to such pollutants had lasting effects on growth after birth.

Fossati, from Pompeu Fabra University in Spain, and colleagues examined 1724 mother-child pairs from the cohort established in 2003-2008. To be included in the study women had to be >16 years old; intention to give birth in the reference hospital, no problems in communication, singleton pregnancy, and non-assisted conception. The team conducted follow-up visits during the third trimester of pregnancy, at birth, and at child ages 1 and 4 years old. What’s more, interview-based questionnaires were issued to the mothers.

At age 4 years old, children underwent a follow-up visit that included height, weight, and waist circumference and blood samples.

The investigators assess nitrogen dioxide (NO₂) in 4, seven-day sampling periods using samplers distributed according to geographic criteria, expected pollution gradients, and population density. Fine particles (PM_2.5) were assess using land-use regression models adjusted to measurements of local background monitoring stations and averaged over the trimesters of pregnancy, the whole pregnancy period, and the first year.

Outcomes included anthropometric measurements (height, weight, and waist circumference); BMI trajectories; blood pressure score; lipids score; and cardio-metabolic risk score.

Fossati and the team tested the link between exposure to air pollution during the first trimester and the outcomes using linear regression models.

A majority of the mothers included were of Spanish origin (94.1%) with a mean delivery age of 32.3 years old. Obesity/overweight prevalence was 31.5%, with 9.6% of children being obese.

The median levels of exposure to NO₂ and PM_2.5 were 28.4 µg/m³ and 15.6 µg/m³. The 2 levels were moderately correlated.

During the first trimester, exposure to NO₂ and PM_2.5 were inversely associated with growth parameters, height, weight, and BMI. Most associations were not statistically significant.

Higher exposure to PM_2.5 during the first trimester was associated with a statistically significant decrease in zWeight (beta for an IQR increase in exposure=−.13; 95% CI, −.23 to −.02) and zBMI (beta=−.12; 95% CI, −.23 to −.01). Exposure to both levels was also associated with reduced risk of being in an accelerated BMI gain trajectory, compared to those with the average trajectory.

Greater exposure to particulate matter during the first trimester of pregnancy was linked with a higher risk of lower weight and BMI at 4 years old. For NO₂, exposure was similar but not statistically significant.

“The implication of our findings is that prenatal exposure to air pollutants has a lasting effect on growth after birth and that this parameter should be followed up at later ages,” Fossati said in a statement.

The study, “Prenatal air pollution exposure and growth and cardio-metabolic risk in preschoolers,” was published online in the journal Environment International.