Placental Pathways: The Impact of Air Pollution (PM _2.5 ) Exposure on Pregnancy Outcomes in three Sub-Saharan African Countries

Abstract Introduction Ambient and indoor fine particle air pollution (PM 2·5 ) estimates have been associated with pregnancy complications. We aimed to link direct personal exposure measurements with placenta-mediated pregnancy complications in three sub-Saharan African countries. Methods We recruited a geographically and energy use stratified sub-sample of 343 rural and urban women who had recently given birth in the PREgnancy Care Integrating translational Science, Everywhere (PRECISE) prospective pregnancy cohort in The Gambia (n = 160), Kenya (n = 105), and Mozambique (n = 78). Individual-level exposure to PM 2·5 was assessed using high-resolution personal monitoring, during both wet and dry seasons. Minute-level data were summarised as mean and peak daily PM 2·5 concentrations, and correlated with maternal blood pressure (BP), gestational age at delivery, fetal growth, and stillbirth, in the index pregnancy. Results 107/343 (32·2%) women experienced pregnancy hypertension, 57/343 (16·0%) women delivered preterm, 203/304 (66·8%) infants with known birthweights were appropriately-grown, and 9/343 (2·7%) infants were stillborn. Higher mean (p=0·012) and peak (p=0·007) exposures were associated with reduced fetal growth velocity, with greater mean exposure associated with small-for-gestational age infants (p=0·016). Greater mean (p=0·017) and peak (p=0·045) PM□.□ exposures were associated with lower birthweight centile. No associations were observed with pregnancy hypertension, pregnancy duration, or stillbirth. Discussion This study provides exploratory evidence that personal PM 2·5 exposure is associated with impaired fetal growth in sub-Saharan Africa. Prioritising access to clean fuels, reducing emissions from informal transport and waste systems, and incorporating personal exposure monitoring into maternal health frameworks could yield measurable improvements in birth outcomes and health equity.