Air Pollution Raises Risk for Spontaneous Preterm Birth

TOPLINE:
Exposure to fine particulate matter (PM2.5) during pregnancy is associated with an increased risk for spontaneous preterm birth, with peak vulnerability in the second trimester. Lower socioeconomic status, limited green space exposure, and extreme heat amplify this risk, whereas living around more trees provides protective effects.
METHODOLOGY:
The researchers conducted a population-based retrospective cohort study to examine the associations of exposures to total PM2.5 and five constituents (black carbon, nitrate, organic matter, and sulfate) during pregnancy with spontaneous preterm birth.
They included 409,037 singleton live births from the Kaiser Permanente Southern California health care system between 2008 and 2018, with mothers having a mean age of 30.3 years at delivery (51% Hispanic).
Daily total PM2.5 concentrations and monthly data on the constituents in California were obtained; mean exposures during the entire pregnancy and in each trimester were calculated.
Spontaneous preterm births were identified through the evaluation of preterm labor visits and were defined as a delivery occurring before 37 weeks following the onset of spontaneous labor, without pregnancy complications, and within 7 days of the last preterm labor visit.
The analysis also examined the effect of factors such as race and ethnicity, education, median household income, exposure to green spaces, wildfire smoke, and temperature.
TAKEAWAY:
Each 2.76 µg/m3 increase in total PM2.5 exposure during pregnancy raised the risk for spontaneous preterm birth by 15% (P < .001), with black carbon showing the highest risk (adjusted odds ratio [aOR], 1.15; 95% CI, 1.12-1.18; P < .001).
Exposure to PM2.5 during the second trimester showed the highest association with spontaneous preterm birth (aOR, 1.10; P < .001), followed by that during the third (aOR, 1.09; P < .001) and first (aOR, 1.07; P < .001) trimesters.
Individuals with lower education levels showed a higher risk for spontaneous preterm birth than those with more than 4 years of college education (P = .003).
Exposure to extreme heat (P < .001) and lower exposure to total green space (P = .003) increased the risk for spontaneous preterm abortion.
IN PRACTICE:
“Targeted and preventive public health interventions among these subpopulations with high risk may be critical for minimizing the burden of spontaneous preterm birth,” the authors wrote.
SOURCE:
The study was led by Anqi Jiao of the program in public health at the Department of Environmental and Occupational Health at the University of California, Irvine. It was published online on November 13, 2024, in JAMA Network Open.
LIMITATIONS:
According to the authors, exposure misclassification was inevitable as individual exposure to PM2.5 was estimated according to census tract-level data without considering personal activity patterns. Only five major PM2.5 constituents were measured due to data availability. Additionally, street-view green space data were considered spatial snapshots, which cannot capture temporal variations, possibly leading to exposure misclassification and biased associations in either direction. 
DISCLOSURES:
The study was supported by the National Institute of Environmental Health Sciences and the California Air Resources Board. One author reported receiving research funding from pharmaceutical and biopharmaceutical companies, which was paid to the institute. Another author reported receiving grants from a medical technology company outside the submitted work.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
 
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