A 19-year-old woman was admitted with acute severe asthma in her eleventh week of pregnancy. Despite vigorous therapy, severe hypoventilation and hypoxemia persisted with mechanical ventilation. Termination of pregnancy resulted in dramatic improvement in airflow. Her course was complicated by pneumonia, barotrauma, and atelectasis accompanying her moribund state. Although she immediately improved following abortion (within 2 hr, peak airway pressure fell from > 70 to 38 cmH2O, without change in plateau pressure), superimposed morbidities improved more slowly, and the patient made a complete recovery. The mechanism accounting for this observation is unknown but the rapid improvement following abortion suggests that increased bronchomotor tone predominated inflammatory changes in causing flow limitation.