- To investigate pregnancy outcome of asthmatic patients. A retrospective population-based study comparing all singleton pregnancies in women with and without asthma was conducted. Patients lacking prenatal care (less than three visits in prenatal care facilities) were excluded from the study. Deliveries occurred during the years 1988-2002. Stratified analysis, using a multiple logistic regression model was performed to control for confounders. During the study period 139 168 singleton deliveries occurred, of which 1.4% in asthmatic patients (n = 963). Using a multivariate analysis, with backward elimination, the following complications were significantly associated with maternal asthma: diabetes mellitus (OR = 1.8, 95%CI 1.5-2.0, p < 0.001), fertility treatments (OR = 1.6, 95%CI 1.3-2.1, p < 0.001), intrauterine growth restriction (IUGR) (OR = 1.5, 95%CI 1.1-1.9, p = 0.004), hypertensive disorders (OR = 1.5, 95%CI 1.2-1.7, p < 0.001) and premature rupture of membranes (OR = 1.2, 95%CI 1.1-1.5, p = 0.013). Higher rates of cesarean deliveries were found among asthmatic patients as compared to the controls (17.1% vs. 11.4%, p < 0.001). This association persisted even after controlling for possible confounders such as failure to progress in labor, mal-presentations, IUGR, etc. No significant differences regarding low Apgar scores (less than 7) at 1 and 5 minutes were noted between the groups (3.9% vs. 4.4%, p = 0.268 and 0.4% vs. 0.6%, p = 0.187, respectively). Likewise, the perinatal mortality rate was similar among patients with and without asthma (1.3% vs. 1.3%, p = 0.798). Pregnant women with asthma are at an increased risk for adverse maternal outcome. This association persists after controlling for variables considered to co-exist with maternal asthma. However, perinatal outcome is favorable. Careful surveillance is required in pregnancies of asthmatic patients, for early detection of possible complications.