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Air pollution, asthma may contribute to preterm birth risk

Exposure to air pollutants for pregnant women with asthma at both early and later gestational weeks carried a higher risk for preterm birth, according to data published in The Journal of Allergy and Clinical Immunology.

“Women with asthma have higher risks for preterm birth after acute exposure to most criteria air pollutants both early (weeks 23, 26, and 29) and later in gestation (weeks 34-36),” Pauline Mendola, PhD, of the division of intramural population health research at Eunice Kennedy Shriver National Institute of Child Health and Human Development in Rockville, Maryland, and colleagues wrote. “Preconception and the first weeks of pregnancy appear to be important windows of susceptibility for preterm birth risk with respect to [carbon monoxide (CO)], [nitrogenoxide (NO_x)], [particulate matter with aerodynamic diameter of less than 10 microns (PM₁₀)] and [particulate matter with aerodynamic diameter of less than 2.5 microns (PM_2.5)] exposure.”

Mendola and colleagues evaluated 223,502 U.S. deliveries with a modified version of the Community Multiscale Air Quality model for preterm birth risk from maternal asthma and exposure to pollutants in the air, according to the abstract. The researchers analyzed CO, ozone (O₃), sulfur dioxide (SO₂), NO_x, PM_2.5 and PM₁₀ exposure for each gestational week, with preterm week 23 to week 36 delivery results compared with women who remained pregnant.

Although there were no significant trends regarding preterm birth prior to gestational week 30, the researchers found preterm birth was more common between weeks 34 and 36, according to the abstract. Specifically, Mendola and colleagues found maternal asthma plus exposure to NO_x, CO and SO₂ between weeks 34 and 36 carried an elevated risk of pre-term birth, with an inverse association between ozone and preterm birth at week 34.

There was a significantly higher risk for preterm birth among women who were exposed to CO and NO_x prior to conception and early in pregnancy. Risk for preterm birth was also higher among women in the last 6 weeks of pregnancy with exposure to PM₁₀, according to the abstract. – by Jeff Craven

Disclosure: Mendola reports no relevant financial disclosures. One researcher reports grant support from Laboratoriolääketieteen edistämissäätiö and Paulo Foundation.