Asthma medication use during pregnancy, wheeze and estimated exposure to ambient nitrogen dioxide

Asthma affects 8-9% of pregnant women in the USA [1]. Since asthma exacerbations during pregnancy can lead to poor pulmonary function, hypoxia and other adverse health outcomes for the mother, fetus and neonate [2, 3], maintaining good control of asthma during pregnancy is recommended for the health of both mother and baby [4]. Reviews of the safety of asthma medication use during pregnancy suggest no or minimal effects on fetal growth and perinatal complications [4-6]. In spite of this, many pregnant women choose to reduce or stop their asthma medications [7].