Association of air purifier usage during pregnancy with adverse birth outcomes: the Japan Environment and Children’s Study

Objective: Previous studies have reported that ambient air pollutants such as PM2.5 can increase the risk of adverse birth outcomes. The objective of this study was to ascertain whether air purifier usage during pregnancy is associated with a lower risk of adverse birth outcomes in a large Japanese birth cohort. Methods: We conducted a prospective cohort analysis using data from the Japan Environment and Children’s Study. Use of air purifiers during pregnancy was assessed using a self-administered questionnaire. Primary outcomes were the prevalence of preterm birth (PTB), small for gestational age (SGA), and low birth weight (LBW). Logistic regression analysis was performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: The prevalence of outcomes was 4.5% for PTB, 7.4% for SGA, and 8.1% for LBW. The crude model analysis revealed that PTB, SGA, and LBW showed lower ORs in the group that used an air purifier, although the association disappeared in the adjusted model except for SGA (OR: 0.94; 95% CI: 0.89, 1.00, p = 0.048) and LBW (OR: 0.93; 95% CI: 0.88, 0.98, p = 0.003). Subgroup analysis stratified by infant sex revealed that the lower OR for LBW was observed only in male infants. Conclusions: Our results suggest that avoiding maternal air pollution exposure during pregnancy may be useful in preventing adverse birth outcomes. These findings provide evidence supporting the development of protective measures against air pollutants in the gestational period by relevant health agencies.