Air pollution in late pregnancy linked to higher NICU admissions for newborns

Exposure to traffic-related pollutants like NO₂ and PM2.5 in the final month of pregnancy increases the risk of neonatal intensive care unit admission by up to 35%, highlighting the need for stricter air quality measures.

Study: Neonatal intensive care admissions and exposure to satellite-derived air pollutants in the United States, 2018. Image Credit: Ivan Marc/Shutterstock.com

In a recent study published in Scientific Reports, researchers explored the impact of exposure to air pollution on the health of newborn infants, or neonates.

Their findings indicate that neonates who were exposed to higher levels of fine particulate matter less than 2.5 microns in diameter (PM2.5) and nitrogen dioxide (NO2) during the month before birth were more likely to be admitted to neonatal intensive care units (NICU).

Background

NICUs monitor and treat several conditions that affect neonates, including those who have faced obstetric complications during birth. One of the risk factors pregnant individuals and their newborn children face is air pollution exposure, either in the short or long term.

Air pollution increases the risk of preterm birth and is linked to complications such as hypertensive disorders or gestational diabetes; these, in turn, raise the likelihood of a neonate being admitted to a NICU.

In the United States, NICU admissions have increased, and treatment at these facilities costs between $5 and $10 billion annually.

While research is clear on the negative impacts that air pollution has on health, few studies address the effects of exposure on the risk of adverse outcomes for neonates, particularly NICU admissions.

About the study

Researchers used satellite data on air pollution to examine how air pollutant exposure shortly before birth affected the probability of a neonate being admitted to a NICU across the United States. They used a cross-sectional design and included all single births for which birth certificates were issued in 2018, resulting in 3,644,722 neonates in the sample.

The outcome used in the analysis was NICU admission; this data was obtained from birth certificates.

Each neonate’s exposure was assessed by examining levels of air pollutants in the county where they were born over the calendar month preceding their birth, including ozone, NO2, and PM2.5.

Researchers focused on a one-month window as admissions to the NICU are often a result of low birth weight, pre-term delivery, or respiratory conditions.

The analysis accounted for the infant’s sex and their mother’s characteristics, including age, ethnicity or race, level of education, body mass index (BMI) before pregnancy, and smoking status.

Findings

Slightly over 8.1% of the neonates born in 2018 had a history of NICU admission. Children of parents under 20 or over 35, those without college degrees, and Black infants were more likely to be admitted. Male neonates were slightly more likely to have NICU admission than females. Admissions did not appear to be affected by the season.

Infants admitted to the NICU showed higher levels of exposure to PM2.5 and NO2 but lower levels of exposure to ozone, except in summer. Generally, NO2 levels were positively correlated with PM2.5 levels but negatively correlated with ozone levels.

In terms of risk of NICU admission, infants in the group with the highest exposure to NO2 had a higher risk of NICU admission, particularly in the summer, though elevated risks were also seen in the spring, fall, and winter. Higher NO2 levels increased the probability of an infant being admitted to the NICU by 30-35%.

Researchers found evidence of similar patterns for exposure to PM2.5, with infants who were most exposed having higher odds of admission to the NICU throughout the year.

Greater exposure to PM2.5 increased the probability of NICU admission by 11-22%. However, ozone exposure did not appear to increase NICU admission risk except in the summer.

Spatial models showed that the mid-Atlantic and the Midwest had the highest risk of NICU admission linked to exposure to NO2.

For PM2.5, risks varied with the season but were persistent in the West Coast and Southeast. There were higher risks across the country in summer, but in winter, the Northeast saw higher risks.

Conclusions

Researchers established that PM2.5 and NO2 exposure close to birth are associated with significantly higher NICU admissions in the United States. These findings support two previous studies that have examined this relationship. However, this study considered a wider exposure window before birth.

Findings consistently show that exposure to air pollution in the short term and overall longer periods before birth adversely affects neonatal health, even in countries that have lower air pollution than global averages, such as the U.S. Air pollution increases inflammation and also has vascular effects, both for the person carrying the child and for the infant.

Reducing the public’s exposure to air pollution can improve overall health as well as lower the risk of adverse outcomes for newborn children.