Acute air pollution exposure and NICU admission: a case-crossover analysis

Neonatal intensive care unit (NICU) admission rates have increased over time. Air pollution is associated with adverse pregnancy outcomes, but the relationship between prenatal air pollution exposure and NICU admission has not been investigated.

In the Consortium on Safe Labor (2002-2008), 27,189 singletons were admitted to the NICU. Modified Community Multiscale Air Quality models estimated exposures for criteria air pollutants and constituents of particles less than or equal to 2.5 microns (PM_2.5). Case-crossover analyses calculated odds ratios and 95% confidence intervals for interquartile range increases in pollutant exposure, comparing exposures during the week of delivery to control periods before and after delivery.

In models that adjusted for PM_2.5, exposure to PM_2.5 constituents during the week before delivery was significantly associated with increased odds of NICU admission: elemental carbon (35%), ammonium ions (37%), nitrate compounds (16%), organic compounds (147%), and sulfate compounds (35%). Odds were also significantly increased by day of and day before delivery exposures to carbon monoxide (4%-5%), nitrogen dioxide (13%), nitrogen oxides (4%-8%), particles less than or equal to 10 microns (2%), particles less than or equal to 2.5 microns (2%), and sulfur dioxide (3%-6%). No associations were observed for ozone.

Acute exposures to PM_2.5 constituents and several traffic-related pollutants during the week before delivery, the day of delivery, and day before delivery appear to increase the odds of NICU admissions. These novel associations suggest infants exposed in utero to common air pollutants may require additional care during the newborn hospital admission.