Effects of cooking with liquefied petroleum gas versus biomass on hemoglobin concentrations in pregnant women: a pre-specified exploratory analysis of the HAPIN trial

Evidence linking household air pollution exposure and blood hemoglobin concentration is lacking. We examine the effect of a liquefied petroleum gas cookstove and fuel intervention on hemoglobin concentration, along with associations between household air pollution exposures and hemoglobin concentration, among pregnant women. We enroll 800 pregnant women each in Guatemala, Peru, India, and Rwanda in an open-label randomized controlled trial (NCT02944682). In 3178 women (intervention=1585; control=1593), we measure hemoglobin concentration and 24-hour personal exposure to particulate matter with an aerodynamic diameter ≤2.5μm (PM_2.5), black carbon (BC), and carbon monoxide (CO) at three timepoints (9-20, 24-28, and 32-36 weeks gestation). We evaluate the effects of the intervention on hemoglobin concentration and conduct exposure-response analyses to examine associations between 24-hour personal exposure to measured pollutants and hemoglobin concentration. We identify a significant increase in hemoglobin in the intervention group (0.074 g/dL, 95% CI: 0.002, 0.145) compared to the control group. In exposure-response analyses, each 1ppm increase in CO exposure is associated with a 0.015 g/dL (95% CI: 0.008, 0.023) increase in hemoglobin. In our analyses, neither PM_2.5 nor BC are associated with hemoglobin concentration. Further research may be needed to examine the biological mechanisms underlying our findings.