The objective of this study was to examine the association between maternal asthma medication use during the periconceptional period and the risk of gastroschisis. In this case-control study, the authors used data on deliveries enrolled in the National Birth Defects Prevention Study (1997-2002) from eight collaborating centers. The cases included 381 infants with isolated gastroschisis, and the controls were 4,121 liveborn infants without malformations. The asthma medications used during the periconceptional period (1 month prepregnancy through the third pregnancy month) were divided into two groups, antiinflammatory and bronchodilator, and analyzed separately. Users of multiple asthma medications during the periconceptional period were also examined. Logistic regression was used to estimate odds ratios and 95% confidence intervals while controlling for maternal age, race/ethnicity, education, smoking, folic acid/vitamin use, and other vasoactive medications. Maternal bronchodilator use showed an elevated statistically significant risk of gastroschisis (adjusted odds ratio = 2.06, 95% confidence interval: 1.19, 3.59). No significant association was found between maternal use of asthma antiinflammatory medications and gastroschisis. Because information on maternal asthma status/severity was not available, the effects of disease on the risk of gastroschisis cannot be ruled out. Additional research is needed in determining whether a real risk exists and for guiding asthma treatment.