Inhaled corticosteroids during pregnancy: a review of methodologic issues.

BACKGROUND There is evidence in the literature that inhaled corticosteroids (ICSs) are safe for pregnant women with asthma and their infants. Although this is useful information about ICS use during pregnancy, some articles must be viewed cautiously because of lack of power and adjustment for potentially important confounding variables. OBJECTIVE To summarize evidence on the potential effects of ICSs to treat asthma in pregnant mothers and their children with particular focus on study power. METHODS Studies published before September 1, 2007, and focusing mainly on ICS use for asthma treatment during pregnancy were researched in Pubmed and the Cochrane Library. Post hoc power calculations were completed using data reported in the published articles. RESULTS Twenty-three studies that evaluated the associations between ICS use during pregnancy and maternal and/or perinatal outcomes were retained. Only six studies on the association between ICS use and maternal outcomes reported significant results; five studies found significant associations between ICS use and perinatal outcomes. Regarding non-significant results, two studies on maternal outcomes and seven studies on perinatal outcomes had a power higher than 80% to detect a relative risk of 1.5 or a mean birth weight difference of 500 g. CONCLUSION While there currently is some degree of evidence to support the safety of ICS use during pregnancy, this review highlights the limited statistical power of several studies published in this area.