Asthma can produce serious maternal and fetal complications. A number of investigators have reported an increased incidence of pre-eclampsia, gestational hypertension, hyperemesis gravidarum, vaginal hemorrhage, toxemia, and induced and complicated labor. Fetal complications include increased risk of perinatal mortality, prematurity, low birth weight, and neonatal hypoxia. In contrast, several studies have failed to confirm some or all of these previous observations. Patients with severe asthma may have the greatest risk for complications during pregnancy, in addition to the risk of maternal morbidity from the asthma. For example, it has been shown that reduced pulmonary function in asthmatic women is associated with an increased likelihood of intrauterine growth retardation. On the other hand, studies in which asthma was successfully controlled have resulted in pregnancy outcomes similar to the general population.