Surgery for heart diseases during pregnancy, especially necessitating cardiopulmonary bypass, is believed to trigger maternal and fetal risks and should be performed only when medical therapy has been unsuccessful to alleviate the cardiac decompensation. A 33-year-old pregnant woman in her 33rd week of gestation was admitted to our hospital. She had rheumatic mitral valvular stenosis and had undergone mitral valve replacement (MVR) with a mechanical prosthesis 11 years earlier in another center. Echocardiography revealed a thrombotic mass obstructing the leaflets of the mechanical mitral valve. Emergency redo bioprosthetic MVR concomitant with caesarean section was performed uneventfully. Both mother and baby were discharged in good condition