Placental pathology associated with household air pollution in a cohort of pregnant women from Dar es Salaam, Tanzania

Background: Smoke from the burning of biomass fuels has been linked with adverse pregnancy outcomes such as low birth weight, stillbirth, and prematurity. Objective: To identify potential underlying mechanisms of adverse perinatal outcomes, we explored the association of placental pathology with household air pollution in pregnant women from urban/periurban Tanzania who cook predominantly with charcoal. Methods: Between 2011 and 2013, we measured personal exposures to fine particulate matter (PM_2.5) and carbon monoxide (CO) over 72 hr among a cohort of Tanzanian pregnant women. Placentas were collected after delivery for examination. Placental pathologies of inflammatory, hypoxic, ischemic/hypertensive, infectious and thrombotic etiologies were diagnosed, blinded to exposure levels. Using multiple logistic regression, we explored the association of PM_2.5and CO exposure with placental pathology. Results: One hundred sixteen women had personal air exposure measurements and placental histopathology available for analysis. PM_2.5and CO exposures were moderate [geometric means (GSD) were 40.5 µg/m³(17.3) and 2.21 ppm (1.47) respectively]; 88.6% of PM_2.5measurements exceeded World Health Organization air quality guidelines. We observed an increase in the odds (per 1-unit increase in exposure on the ln-scale) of fetal thrombotic vasculopathy (FTV) both with increasing PM_2.5[adjusted odds ratio (aOR) = 5.5; 95% CI: 1.1, 26.8] and CO measurements (aOR = 2.5; 95% CI: 1.0, 6.4) in adjusted models only. FTV also was more common among pregnancies complicated by stillbirth or low birth weight. Conclusions: Fetal thrombosis may contribute to the adverse outcomes associated with household air pollution from cook stoves during pregnancy. Larger studies are necessary for confirmation.