Background: Inhaled corticosteroids are recommended as first-line therapy for pregnant women with moderate to severe asthma, although the effects on pregnancy outcome are uncertain. A low compliance with the recommendations might lead to inadequate control of asthma, which has been associated with adverse outcomes both for the mother and the infant. Objective: To investigate whether the reported use of inhaled budesonide (Pulmicort) during pregnancy influences birth outcome. Methods: Data were derived from the Swedish Medical Birth Register, which includes 99% of births in Sweden. During 1995 to 1998, 293,948 newborn infants were identified. Pregnancy outcomes were compared for mothers in Sweden reporting asthma medication usage with those reporting no asthma medication usage. Results: The 2968 mothers who reported use of inhaled budesonide during early pregnancy gave birth to infants of normal gestational age, birth weight, and length, with no increased rate of stillbirths or multiple births. The rate of caesarean births was higher among mothers who used asthma medication during their pregnancy than among the control group. Conclusions: The use of inhaled budesonide in Sweden is not linked with any clinically relevant effects associated with pregnancy outcome.