A 32-year-old woman was referred to our hospital during the 35th week of pregnancy because of chest pain and dyspnea. The cesarean section was performed and a healthy infant was delivered. On the 16th hospital day, she developed heart failure. Echocardiograms revealed protrusion of the mitral valve into the left atrium in systole, vegetation and worsening of mitral regurgitation. CT showed splenic infarction. Mitral valve replacement was performed after inflammatory findings were improved by antibiotics. We reported here a case of infective endocarditis during the perinatal period.