A 38-year-old woman on medical therapy for Basedow disease and hypertension with a history of recent heart failure became pregnant. At the 13th week of gestation, her echocardiography showed pulmonary hypertension with 63 mmHg of estimated systolic pulmonary arterial pressure. At the 26th week of gestation, she was admitted to our hospital with dyspnea and uncontrolled hypertension. After medical treatments, elective caesarean section was scheduled at the 30th week of gestation. While monitoring continuously arterial blood pressure and central venous pressure, continuous infusion of prostaglandin E1 was initiated. After epidural anesthesia had been established, surgical procedure was safely performed. The patient was discharged 9 days after surgery, and her estimated systolic pulmonary arterial pressure dropped to 35 mmHg on echocardiography 2 months after the operation. We speculate that pregnancy induced her severe pulmonary hypertension.