OBJECTIVE:To determine neonatal an d maternal out-comes stratified by asthma severity during pregnancy by using the 1993National Asthma Educa tion Program Working Group on Asthma and Pregnancy definitions of asthma severity.The primary hypoth esis was that moderate or severe asthmatics would have an in creased incidence of delivery at<32weeks of gestation compared with n onasth-matic controls.METHODS:This was a m ulticenter,prospective,observational cohort study conducted over 4years at 16university hospital cent ers.Asthma severity was defined according to the National As thma Education Pro-gram Working Group on Asthma and Preg nancy classifica-tion and modified to include medication requirements.This study had 80%power to detect a 2-to 3-fold increase in delivery less than 32weeks of gestation among the cohort with the moderate or severe asthma co mpared with controls.Secondary outcome measures included obstetrical and neonatal outcomes.RESULTS:The fin al analysis included881nonasthmatic controls,873with mild asthma,814with moderate,and 52with severe asthma.There were no significant differences in the rate s of preterm delivery less than 32weeks(moderate or severe 3.0%,mild 3.4%,controls 3.3%;P =.873)or less than 37weeks of ges-tation.There were no significant di fferences for neonatal outcomes except discharge diagnosis of neonatal sepsis a-mong the mild group compared with con trols,adjusted odds ratio 2.9,95%confidence interval 1.2,6.8.There were no significant differences for mate rnal complications except for an increase in overall cesarean d elivery rate among the moderate -or -severe group compared with controls(adjusted odds ratio 1.4,95%confidence interval 1.1,1.8).CONCLUSION:Asthma was not associa ted with a significant increase in preterm delivery or other adverseperinatal outcomes other than a disc harge diagnosis of neonatal sepsis.Cesarean delivery rate was increased a-mong the cohort with moderate or severe asthma. OBJECTIVE: To determine neonatal an d maternal out-comes stratified by asthma severity during pregnancy by using the 1993 National Asthma Educa- tion Program Working Group on Asthma and Pregnancy definitions of asthma severity. The primary hypothyroid was that moderate or severe asthma would have an in creased incidence of delivery at <32 weeks of gestation compared with n onasth-matic controls. METHODS: This was am ulticenter, prospective, observational cohort study conducted over 4years at 16university hospital centrs. Asthma severity was defined according to the National As thma Education Pro -gram Working Group on Asthma and Preg nancy classifica- tion and modified to include to meet the requirements of this study had 80% power to detect a 2-to 3-fold increase in delivery less than 32 weeks of gestation among the cohorts with the moderate or severe asthma co mpared with controls. Secondary counseling measures included obstetrical and neonatal outcomes.RESULTS: The fin al analysis included881nonasthm atic controls, 873 with mild asthma, 814 with moderate, and 52 with severe asthma. There were no significant differences in the rate s of preterm delivery less than 32 weeks (moderate or severe 3.0%, mild 3.4%, controls 3.3%; P = .873) or less than 37 weeks of ges-tation. There were no significant di fferences for neonatal outcomes except discharge diagnosis of neonatal sepsis a-mong the mild group compared with con trols, adjusted odds ratio 2.9, 95% confidence interval 1.2, 6.8.There were no significant differences for mate rnal complications except for an increase in the overall-es-prognostic group compared with controls (adjusted odds ratio 1.4, 95% confidence interval 1.1, 1.8) .CONCLUSION: Asthma was not associa ted with a significant increase in preterm delivery or other adverse perinatal outcomes other than a disc harge diagnosis of neonatal sepsis. Cesarean delivery rate was increased a-mong the cohort with moderate or severe asthma.