Pregnancy in the setting of pulmonary hypertension and Eisenmenger physiology is associated with a substantial maternal and fetal risk. Such patients are advised against pregnancy. We report a case of a woman with an Eisenmenger atrial septal defect diagnosed during the last trimester of pregnancy. On presentation, she was critically ill and there was evidence of fetal distress. She was emergently treated with IV epoprostenol, and her status improved. She underwent cesarean section and delivered a male infant with Apgar scores of 8 and 9. Her dyspnea improved, and she was characterized as World Health Organization functional class II on a subsequent clinical visit. Although pregnancy should be discouraged in women with Eisenmenger syndrome, we have demonstrated that IV epoprostenol successfully treated a woman with Eisenmenger syndrome diagnosed in the third trimester.