Asthma in pregnancy has been associated with maternal and fetal morbidity and mortality. This study examines the relations of asthma in pregnancy, its severity and its treatment to the labor process, maternal and fetal parameters. Hundred and one consecutive asthmatic women, who gave birth to single babies between November 1993 and November 1994 at the Soroka Medical Center were studied. A group of 77 nonasthmatic women, matched for age and ethnic origin, who gave birth to single babies during the same period served as controls. A larger percentage of asthmatic women suffered from respiratory and urinary tract infections than in the control group (p < 0.001). Severe asthma was associated with a higher rate of infections than milder asthma (p = 0.01). The incidence of smoking was higher among asthmatic women than among controls (p = 0.037). No association was found between socioeconomic status and smoking or infections. No association was found between maternal asthma or maternal use of corticosteroids and the following: maternal hypertension, maternal diabetes, low birth weight (<2,500 g), preterm delivery (<37 weeks), adequacy of weight to gestational age and Apgar scores. Three infants with congenital heart defects were born to asthmatic mothers. When the presentation of the fetus was not cephalic, all the asthmatic women were delivered by cesarean section, versus only 60% in the control group (p = 0.08). Labor was induced with oxytocin more often in the asthma group than in the control group (p = 0.07). We conclude that the labor and neonatal outcome in pregnant asthmatic women treated medically is good, even when asthma is severe and when the patient is treated with corticosteroids. There is, however, a relation between asthma in pregnancy, especially if severe, and predisposition to infections.