How maternal BMI modifies the impact of personalised asthma management in pregnancy

ABSTRACT Background Maternal asthma is associated with perinatal complications and respiratory illness in offspring. Obesity increases asthma exacerbation risk in pregnancy and risk of wheeze in offspring. Objectives In this secondary analysis of a randomised controlled trial (RCT), we investigated the influence of maternal body mass index (BMI), gestational weight gain (GWG) and fractional exhaled nitric oxide (F E NO)-based management on asthma exacerbations in pregnancy and offspring wheeze. Methods 220 women were randomised to asthma treatment adjustment according to symptoms (control group), or F E NO and symptoms (F E NO group). Exacerbations were recorded prospectively. Height and weight were measured at baseline, and in late pregnancy. GWG was categorised according to Institute of Medicine (IOM) guidelines. A validated parent-completed questionnaire assessed infant wheeze-related outcomes. Results F E NO based management was associated with a significantly lower incidence rate ratio (IRR) for maternal exacerbations in non-obese mothers (0.52, 95% CI 0.31–0.88, P=0.015, n=129), and women with GWG within recommendations (0.35, 95% CI 0.12-0.96, P=0.042, n=43), but not for obese mothers (0.59, 95% CI 0.32-1.08, P=0.089, n=88), or women with excess GWG (0.58, 95% CI 0.32-1.04, P=0.07, n=104). Recurrent bronchiolitis occurred in 5.3% (n=1) of infants born to non-overweight mothers, 16.7% (n=3) of infants of overweight mothers and 21.7% (n=5) of infants of obese mothers in the control group. In the F E NO group, two infants of obese mothers had recurrent bronchiolitis (7.1%, P=0.031). Conclusions The benefits of F E NO -based management are attenuated among obese mothers and those with excess GWG, indicating the importance of weight management in contributing to improved asthma management in pregnancy.