Risk of low birth weight and stillbirth associated with indoor air pollution from solid fuel use in developing countries.

Exposure to indoor air pollution from solid fuel use (IAP) has been linked to approximately 1.5 million annual deaths (World Health Organization (http://www.who.int/indoorair/publications/fuelforlife/en/index.html)) due to acute lower respiratory infections in children <5 years of age and chronic obstructive lung disease and lung cancer in adults. Emerging evidence suggests that IAP increases the risk of other conditions, including adverse pregnancy outcomes. To establish the relation of IAP with birth weight and stillbirth, systematic reviews with meta-analyses were conducted. Studies reporting outcomes of mean birth weight, percentage of low birth weight (LBW; <2,500 g), and/or stillbirth and assessing IAP were identified. Five LBW studies (of 982) and 3 stillbirth studies (of 171) met inclusion criteria for the reviews. Fixed-effect meta-analyses (I(2) = 0%) found that IAP was associated with increased risk of percentage LBW (odds ratio = 1.38, 95% confidence interval: 1.25, 1.52) and stillbirth (odds ratio = 1.51, 95% confidence interval: 1.23, 1.85) and reduced mean birth weight (-95.6 g, 95% confidence interval: -68.5, -124.7). Evidence from secondhand smoke, ambient air pollution, and animal studies--and suggested plausible mechanisms--substantiate these associations. Because a majority of pregnant women in developing countries, where rates of LBW and stillbirth are high, are heavily exposed to IAP, increased relative risk translates into substantial population attributable risks of 21% (LBW) and 26% (stillbirth).