1. In this randomized controlled trial, replacing biomass stoves with those using liquefied petroleum gas (LPG) during pregnancy did not reduce stunting in infants at one year despite reductions in household air pollution.
2. There was no appreciable difference in stunting in infants at six months between the biomass cookstove and liquefied petroleum gas cookstove groups.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Household air pollution is a significant environmental risk factor in low- and middle-income countries and arises from incomplete combustion of biomass fuels. Exposure to household air pollution is linked to poor health outcomes, including increased stunting rates in children, which may lead to lower educational attainment and economic performance in adulthood. The World Health Organization (WHO) defines childhood stunting as a length or height that is greater than two standard deviations below the median standard set by the Multicenter Growth Reference Study (MGRS). Several mechanisms on how household air pollution impacts child growth, including prenatal and postnatal oxidative stress and impaired immune function leading to increased nutrient requirements, have been suggested. This study aimed to assess the effects of replacing biomass cookstoves with their LPG counterparts on stunting in infants. Overall, despite successful reductions in household air pollution, the use of LPG cookstoves during pregnancy did not reduce stunting in infants at one year of age, with no appreciable differences in the mean length-for-age z scores between the infants born to women using LPG or biomass cookstoves. Moreover, no appreciable differences were observed at six months of age. The study was limited by the indirect measurement of household air pollution exposure in infants using a beacon emitter.
Click to read this study in NEJM
In-Depth [randomized controlled trial]: The Household Air Pollution Intervention Network (HAPIN) trial is a randomized controlled trial that aimed to evaluate the effect of replacing biomass cookstoves with LPG cookstoves on stunting in infants. Pregnant women between 18 to 34 years of age with a singleton pregnancy between 9 to 20 weeks gestation from low- to middle-income countries were enrolled in the trial and randomly assigned in a 1:1 ratio to the LPG group or the biomass (control) group. Pollutants were measured a total of six times: three times in the women during pregnancy and three times in the infants at three, six, and 12 months of age. The primary outcome was stunting in the infants at 12 months of age (as defined by the WHO). Secondary outcomes included the length-for-age z score at 12 months and stunting at six months of age. Overall, 3,200 pregnant women across four low- to middle-income countries were enrolled. At 12 months, stunting occurred in 321 of 1,171 infants (27.4%) born to women in the LPG group versus 299 of 1,186 infants (25.2%) born to women in the control group (relative risk, 1.10; 98.75% Confidence Interval [CI], 0.94 to 1.29; p=0.12). No appreciable difference was observed in the mean length-for-age z score at 12 months (mean difference, -0.03; 95% CI, -0.11 to 0.05) or in stunting at six months of age (relative risk, 1.01; 95% CI, 0.86 to 1.19) between the two groups. In summary, this study demonstrated that replacing biomass cookstoves with their LPG counterparts during pregnancy did not reduce stunting in infants at one year of age despite large reductions in household air pollution.
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