Prenatal Harmattan exposure and birth size: identifying sensitive windows in pregnancy

The Harmattan season (approximately December to March) in Western Africa is characterized by dry, dusty trade winds blowing from the Sahara Desert toward the Gulf of Guinea and is associated with marked increases in fine particulate matter and other air pollutants, cooler temperatures, and crop reductions. The season has been linked with several negative health effects, though impacts on pregnancy outcomes are unknown. We leveraged data from the Ghana Randomized Air Pollution and Health Study (GRAPHS) to determine whether prenatal exposure to the Harmattan season impacts newborn size and whether there are critical windows of exposure.

GRAPHS enrolled 1,414 pregnant women from Kintampo, Ghana from 2013 to 2015. We employed distributed lag models (DLMs) to examine time-varying associations between prenatal exposure to the Harmattan season (yes/no) for each week of gestation and birth weight, length, and head circumference among infants liveborn ≥ 37 weeks.

Analyses included n = 1,261 mother-infant pairs. Harmattan exposure was associated with smaller head circumference across gestation and DLMs identified sensitive windows in weeks 1-11 and 15-34. These effects were only significant among infant males. No impact of Harmattan on birth weight or birth length was identified.

Our analyses suggest prenatal exposure to the Harmattan season is associated with negative impacts on newborn size and specifically head circumference; exposure during certain gestational windows appears to have a greater impact than others. Climate change threatens to make Harmattan more severe secondary to increased desertification; we therefore need a better understanding of its health effects during pregnancy.