A 23-year-old woman, gravida 1, para, 0, was transferred at 29 weeks and 2 days gestation for management of infective endocarditis (IE). Based on vegetations attached to the mitral valve by echocardiography and positive blood cultures for Streptococcus mitis, the diagnosis of IE was made at the referring hospital. On admission to our hospital, echocardiography demonstrated a large vegetation and prolapse of the mitral valve with severe valve regurgitation. The fetal heart rate was 140/min. Ultrasound examination demonstrated an appropriate for gestational age 1,350 g fetus in vertex presentation. The day after admission, her membrane ruptured spontaneously, and she delivered a male infant by caesarean section at 29 weeks and 3 days of gestation. On the 42nd day of hospitalization, the mitral valve was reconstructed by quadrangular resection of the posterior commissure and annuloplasy with a prosthetic ring. A histological examination of specimens of the resected leaflets indicated that IE was active. One year later, the patient delivered a healthy infant without any complications by a caesarean section. The latest Doppler study demonstrated trivial mitral regurgitation and a mitral valve area of 2.5 cm2.