Influence of maternal body mass index and macrophage activation on asthma exacerbations in pregnancy

Background: Obesity is a risk factor for exacerbations of asthma, but the mechanisms of this effect in pregnancy are unknown. Objective: This study determined the influence of maternal body mass index, gestational weight gain, eosinophilic inflammation, and systemic macrophage activation on the risk of exacerbations during pregnancy. Methods: Women with asthma (n = 164) participated in the study. Body mass index recorded at baseline (17 weeks gestation) was categorized as healthy weight (18.5-24.9 kg/m²), overweight (25-29.9 kg/m²), or obese ( > 30 kg/m²). Exacerbations requiring medical intervention were recorded prospectively. Asthma control, medication use, and fractional exhaled nitric oxide were assessed monthly; additional visits occurred during exacerbations. Peripheral blood was collected at baseline for the measurement of eosinophils, soluble CD-163, C-reactive protein, and IL-6. Results: Exacerbations occurred in a higher proportion of overweight (51.1%) and obese (48.4%) women compared with healthy weight women (25%; P =.026). Excess weight gain during pregnancy was not associated with exacerbation risk. Macrophage activation (elevated serum soluble CD-163) was associated with exacerbations requiring oral corticosteroids (P =.043), whereas high peripheral blood eosinophils or fractional exhaled nitric oxide were not associated with exacerbation or oral corticosteroid use. Conclusions: Being overweight or obese confers a greater risk of asthma exacerbation during pregnancy, and may be due to systemic macrophage activation.