Air Pollution Tied to Newborn Intensive Care Admissions

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Infants born to women exposed to high levels of air pollution in the week before delivery are more likely to be admitted to a newborn intensive care unit (NICU), suggests an analysis by researchers at NIH. Depending on the type of pollution, chances for NICU admission increased from about 4 percent to as much as 147 percent, compared to infants whose mothers did not encounter high levels of air pollution during the week before delivery. The study was led by Dr. Pauline Mendola of NICHD’s Epidemiology Branch. It appears in Annals of Epidemiology.

“Short-term exposure to most types of air pollutants may increase the risk for NICU admission,” Mendola said. “If our findings are confirmed, they suggest that pregnant women may want to consider limiting their time outdoors when air quality advisories indicate unhealthy conditions.”

Previous studies have linked elevated levels of certain kinds of air pollutants to higher risks for gestational diabetes and preeclampsia, a blood pressure disorder of pregnancy. Earlier research also has shown that infants born to women exposed to high levels of air pollutants are at risk for preterm birth, of being small for their gestational age at birth and of growing more slowly than normal in the uterus. Given these associations, the study authors sought to determine whether prenatal exposure to air pollution might increase the chance for NICU admission.

Researchers analyzed data from the Consortium on Safe Labor, which compiled information on more than 223,000 births at 12 clinical sites in the United States from 2002 to 2008. They linked records from more than 27,000 NICU admissions to data modified from the Community Multiscale Air Quality Modeling System, which estimates environmental pollution concentrations in the United States. Researchers matched air quality data in the area where each birth occurred to the week before delivery, the day before delivery and the day of delivery. They then compared these time intervals to air quality data 2 weeks before delivery and 2 weeks after delivery to identify risk of NICU admission associated with pollution levels.

Researchers do not know why exposure to air pollution might increase the chances for NICU admission. They theorize, however, that pollutants increase inflammation, leading to impaired blood vessel growth, particularly in the placenta, which supplies oxygen and nutrients to the developing fetus.