TOPLINE: 

Pregnant women with asthma who were exposed to wildfire smoke for 10 days or more or early in pregnancy were more likely to deliver infants with low birth weight, preterm birth, or admission to neonatal ICU.

METHODOLOGY: 

• Researchers conducted a multicenter cohort study in Australia to evaluate whether exposure to wildfire smoke during pregnancy was associated with poor newborn outcomes in women with asthma.
• They included 1275 pregnant women with asthma (mean age, 30.7 years) at 12-23 weeks of pregnancy between March 2013 and October 2019.
• Average daily exposure to wildfire smoke, derived from the number of days with smoke, and wildfire-related particulate matter (PM)_2.5 at home was estimated using data on air monitor and satellite-derived smoke, meteorological data, and information on land use.
• Hospital birth records were used to retrieve data on birth weight, low birth weight (< 2500 g), length of pregnancy, preterm birth (< 37 weeks), small for gestational age, admission to the neonatal ICU, and cesarean delivery.
• Researchers analyzed exposure using total days of wildfire smoke, by month of pregnancy, and by comparing the pregnancies during the 2019-2020 bushfire season with those in earlier summers.

TAKEAWAY:

• Women with asthma exposed to wildfire smoke on 10 or more days during pregnancy had increased odds of having babies with low birth weight (adjusted odds ratio [aOR], 4.15; 95% CI, 1.24-13.87), preterm birth (aOR, 2.84; 95% CI, 1.13-7.16), or neonatal ICU admission (aOR, 5.00; 95% CI, 1.40-17.81).
• Each 1-µg/m³ rise in wildfire-related PM_2.5 in the third month of pregnancy was linked to increased odds of preterm birth (aOR, 1.21; 95% CI, 1.04-1.39) and neonatal ICU admission (aOR, 1.21; 95% CI, 1.03-1.42). Exposure in the second month was linked to increased odds of cesarean section (aOR, 1.26; 95% CI, 1.09-1.47).
• Pregnancies overlapping the 2019-2020 bushfire season were associated with significantly greater odds of low birth weight, preterm birth, and neonatal ICU admission than pregnancies from earlier summers.
• Pregnancies with shorter cumulative exposures (1-4 or 5-9 smoke days) had no significant association with any adverse neonatal outcomes.

IN PRACTICE:

"Policy and practice supporting reduced exposure by pregnant women with asthma during a wildfire event could be of benefit in reducing adverse short- and long-term health outcomes in these high-risk infants," the researchers of the study wrote.

SOURCE:

The study was led by Bronwyn K. Brew, PhD, of University of Newcastle in New South Wales, Australia. It was published online on February 18 in the American Journal of Obstetrics and Gynecology.

LIMITATIONS:

The small sample size produced wide CIs and lowered precision. Researchers used outdoor pollution data as a proxy for personal exposure, which did not reflect indoor protection or time spent away from home. The exposed group had more twins, but their number was insufficient to determine whether risks differed from singletons.

DISCLOSURES:

The study received funding from the National Health and Medical Research Council of Australia and the Australian Medical Research Future Fund. One author reported receiving speaker's payments for educational activities from AstraZeneca, GlaxoSmithKline, and Novartis. All other authors reported having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.