Air purifiers during pregnancy beneficial for fetal growth

The use of portable HEPA (high-efficiency particulate air) filter air cleaner during pregnancy is associated with increased birth weight, in babies born at term, according to a new study published in the journal Environment International.

It is already known that exposure to fine particulate matter (PM_2.5). Prabjit Barn, Faculty of Health Sciences, Simon Fraser University, Canada, and colleagues conducted the study to assess the effect of portable HEPA filter air cleaner use during pregnancy on fetal growth.

"Portable HEPA filter air cleaners are a promising intervention to lower PM_2.5 exposures at the household level. Their use has been shown to reduce indoor residential PM_2.5 concentrations by 29–62%," write the authors.

The Ulaanbaatar Gestation and Air Pollution Research (UGAAR) study is a single-blind randomized controlled trial conducted in Ulaanbaatar, Mongolia. It recruited 540 non-smoking pregnant women at ≤18 weeks gestation, who were randomized to an intervention (1–2 air cleaners in homes from early pregnancy until childbirth) or control (no air cleaners) group (272 control and 268 intervention). Participants were not blinded to their intervention status. Unadjusted linear and logistic regression and time-to-event analysis were used to evaluate the intervention.

The primary outcome was birth weight. Secondary outcomes included gestational age-adjusted birth weight, birth length, head circumference, gestational age at birth, and small for gestational age.

• There were 465 live births and 28 losses to follow up.


• A 29% (95% CI: 21, 37%) reduction in indoor PM_2.5concentrations with portable HEPA filter air cleaner use was reported in the previous study.


• The median (25th, 75th percentile) birth weights for control and intervention participants were 3450 g (3150, 3800 g) and 3550 g (3200, 3800 g), respectively (p = 0.34).


• The intervention was not associated with birth weight (18 g; 95% CI: −84, 120 g), but in a pre-specified subgroup analysis of 429 term births, the intervention was associated with an 85 g (95% CI: 3, 167 g) increase in mean birth weight.

"In this single-blind RCT in a community exposed to very high air pollution concentrations, portable HEPA cleaner use during pregnancy was not associated with improvements in fetal growth among all births. However, the intervention was associated with an 85 g increase in term birth weight," concluded the authors.

"In the long-term, strategies to reduce community-wide air pollution concentrations are needed to ensure that the benefits of exposure reduction are available to all."