Primary pulmonary hypertension is a rare, incurable, and progressive disease. When it is associated with pregnancy, the mortality rises to > 50%. We report a patient who was diagnosed with severe pulmonary hypertension of unknown cause in the twenty-second week of gestation. She was treated with an oral calcium-channel blocker and low-molecular-weight heparin and underwent delivery by cesarean section with good maternal and fetal outcome. Patients with severe pulmonary hypertension should, however, avoid pregnancy because of the high mortality, although cases have been reported with positive outcome.