August 13, 2019

Air pollution associated with increase in NICU admissions

At a Glance

  • Exposure to air pollution just before birth appeared to increase the odds that an infant would spend time in the neonatal intensive care unit (NICU).
  • If these results are confirmed, pregnant women may be advised to limit their time outdoors on days with poor air quality.
Pregnant woman overlooking a city The study adds to growing evidence about the effects of exposure to air pollution during pregnancy. Petrenkod / iStock / Getty Images Plus

Having a newborn child admitted to the NICU is a traumatizing experience for families. NICU admission can limit contact between parents and infants during the first days of life, which may have consequences for later development. Time in the NICU is also very expensive, putting stress on families and on the health care system.

NICU admissions have been rising in the U.S., but the reasons why are unclear. Some factors that appear to increase the odds of NICU admission have been identified. These include certain health conditions in mothers and genetic risk factors.

Scientists are examining whether environmental exposures might increase the risk of NICU admission. If such exposures could be identified, expectant mothers could be cautioned to avoid them whenever possible.

A team led by Dr. Pauline Mendola of NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) looked at links between exposure to air pollution immediately before birth and the risk of NICU admission. The researchers studied more than 220,000 women who gave birth between 2002 and 2008 at 19 hospitals across the country.

Air pollution data were used to estimate the women’s exposures to specific air pollutants. The team examined levels the week before delivery, the day before delivery, and the day of delivery. For comparison, they also estimated pollution exposures during two control periods: two weeks before delivery and two weeks after delivery.

The team included chemicals commonly found in emissions from cars and trucks. They also modeled exposures to a class of fine particles called PM2.5, which have previously been associated with many health problems. The results were published online on July 12, 2019, in Annals of Epidemiology.

About 27,000 women in the study had an infant admitted to the NICU. Exposure to almost all measured pollutants the day before or day of delivery was associated with an increased risk of NICU admission. This increased risk ranged from 2% to 127%, depending on the specific pollutant.

In the full week before birth, only exposure to certain components of PM2.5 was associated with an increased risk of NICU admission. This increased risk ranged from 16% to 147%.

Other studies will be needed to explain how exposure to air pollution may increase the risk of NICU admission. Many factors could play a role, including inflammation in the body in response to pollution exposure. This inflammation could have harmful effects on the placenta—the tissue in the uterus that surrounds and protects the fetus.

“Short-term exposure to most types of air pollutants may increase the risk for NICU admission,” Mendola says. “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.”

Related Links

References: Acute air pollution exposure and NICU admission: a case-crossover analysis. Seenia I, Williams A, Nobles, C, Chen Z, Sherman S, Mendola P. 2019 July 12.

Funding: NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).