The maternal death rate and rate of preterm delivery associated with pneumonia during pregnancy have not decreased since the introduction of antibiotics four decades ago. We retrospectively reviewed 25 cases of pneumonia during pregnancy; these cases occurred among 32,179 deliveries. Medical complications included: bacteremia, 16%; empyema, 8%; atrial fibrillation, 4%; respiratory failure necessitating mechanical ventilation, 20%. Obstetric complications occurring during the pneumonia episode included: preterm labor, 44%; preterm delivery, 36%. A patient with cystic fibrosis died; one stillbirth and two neonatal deaths occurred. Underlying maternal disease was significantly associated with maternal medical complications (p = 0.023) and preterm delivery (p = 0.012). Significant medical and obstetric complications continue to occur frequently despite modern antimicrobial, tocolytic, and supportive therapy. Underlying maternal disease, including acquired immunodeficiency syndrome and cystic fibrosis, was associated with preterm delivery and neonatal and maternal death.