Management of asthma in pregnancy guided by measurement of fraction of exhaled nitric oxide: a double-blind, randomised controlled trial

Asthma exacerbations during pregnancy are common and can be associated with substantial maternal and fetal morbidity. Treatment decisions based on sputum eosinophil counts reduce exacerbations in non-pregnant women with asthma, but results with the fraction of exhaled nitric oxide (F NO) to guide management are equivocal. We tested the hypothesis that a management algorithm for asthma in pregnancy based on F NO and symptoms would reduce asthma exacerbations. We undertook a double-blind, parallel-group, controlled trial in two antenatal clinics in Australia. 220 pregnant, non-smoking women with asthma were randomly assigned, by a computer-generated random number list, before 22 weeks' gestation to treatment adjustment at monthly visits by an algorithm using clinical symptoms (control group) or F NO concentrations (active intervention group) used to uptitrate (F NO >29 ppb) or downtitrate (F N