Prenatal wildfire exposure in women with asthma adversely affects neonatal outcomes

Exposure to wildfire smoke early in pregnancy in women with asthma carries an increased risk of adverse neonatal outcomes, as reported in a study.

The study included 1,275 pregnant women (mean age 30.7 years, 85 percent White, 69 percent had overweight or obesity, 15 percent were smokers) with asthma from six antenatal clinics across four cities in Australia, recruited at 12–23 weeks of gestation. Prenatal wildfire smoke exposure days and daily wildfire-related particulate matter ≤2.5 μm concentrations were evaluated by residence.

Neonatal outcomes included birthweight, low birthweight (<2,500 g), gestational length, preterm birth (<37 weeks), neonatal intensive care unit (NICU) admission, and caesarean delivery.

The prenatal mean daily particulate matter ≤2.5 μm concentration was 7.6 μg/m³, with the median number of prenatal cumulative days of wildfire smoke exposure of 3. Prenatal exposure to ≥10 cumulative wildfire smoke days was associated with increased odds of low birthweight (adjusted odds ratio [aOR], 4.2, 95 percent confidence interval [CI], 1.2–13.9), preterm birth (aOR, 2.8, 95 percent CI, 1.1–7.2), and NICU admission (aOR, 5, 95 percent CI, 1.4–17.8).

Exposure to wildfire-related particulate matter ≤2.5 μm in the second and third gestational months was likewise associated with preterm birth, small for gestational age, and NICU admission.

In a natural experiment comparing exposure during the 2019–2020 summer extreme wildfire period with historical controls, prenatal exposure was associated with two- to fourfold greater odds of low birthweight (aOR, 2.6, 95 percent CI, 1.1–6.2), preterm birth (aOR, 2.5, 95 percent CI, 1.2–5.2), and NICU admission (aOR, 4.8, 95 percent CI, 2.0–11.2).

The findings suggest that measures to reduce wildfire smoke exposure early in pregnancy could be beneficial.