Study supports link between air pollution, adverse birth outcomes
Maternal exposure to air pollution during pregnancy increased neonates’ odds of low birth weight and being born small for gestational age, according to data in Environmental Research.
The findings expanded upon those reported in a University of California, San Francisco, study published in 2013, which used data on global pollution.
Researchers conducted a population-based study of an Israeli cohort to address “concern regarding the impact of particulate matter air pollution of the growth and development of fetuses,” Hagai Levine, MD, MPH, postdoctoral researcher in reproductive epidemiology at Mount Sinai and professor of epidemiology at Hebrew University-Hadassah School of Public Health in Jerusalem, told Healio.
Creating a study cohort
Using data from Maccabi Healthcare Services, Levine and colleagues identified 381,265 singleton neonates born to 223,780 mothers (mean births per mother, 2.3; standard deviation, 1.3) from 2004 to 2015. Babies were born between 24- and 42-weeks’ gestation and weighed between 500 g and 5,000 g.
Researchers assessed maternal exposure to fine particulate matter (PM2.5) by linking satellite data on a spatiotemporal air pollution model with the neonates’ date of birth and maternal residence. They used these data to calculate mean PM2.5 exposure for the duration of the pregnancy.
Of note, siblings were included for analysis if they fit the study criteria, which helped mediate variability attributable to mothers.
Air pollution increases poor birth outcomes
The mean PM2.5 level during pregnancy was 21.8 µg/m3, with the highest values among summer births and lowest in low socioeconomic areas.
Adjusted modeling revealed that a 10 µg/m3 increase in PM2.5 during pregnancy increased the odds of low birth weight (OR = 1.25; 95% CI, 1.09-1.43) and increased the odds of being born small for gestational age (OR = 1.15; 95% CI, 1.06-1.26).
Although maternal air pollution exposure in any trimester affected birth outcomes, the analysis revealed that exposure during the second and third trimesters more strongly correlated with adverse birth outcomes than exposure during the first trimester.
Mothers who were underweight before pregnancy were more susceptible to the impact of air pollution compared with women who were obese before pregnancy. Underweight mothers were also more likely to have babies who had a low birth weight (underweight OR = 1.86 vs. obese OR = 1.15) and who were small for gestational age (underweight OR = 1.6 vs. obese OR = 1.06).
The researchers also found that associations between PM2.5 and birth outcomes were strongest for the firstborn child and for girls.
Given these findings, Levine suggested implementing interventions that may prevent poor birth outcomes related to pollution.
“We should instruct mothers how to avoid exposure on high pollution days,” Levine said. “We should improve ventilation. We should reduce exposure at the community, national and international level by better regulation.”
The researchers cautioned that data on pre-pregnancy BMI, alcohol intake and education were missing for some mothers, which may skew their findings. Also, they were unable to track whether a mother changed residence during pregnancy.
Moving forward, Levine highlighted the need for more research on the effect of climate change on birth outcomes.
“We would like to study [the impact of] the combination of exposure to air pollution and to air temperature ... on fetal health, of special importance in light of climate change,” he said.