Women with underlying rheumatic heart disease, even if well compensated, can easily be affected by acute heart failure caused by out-of-the-ordinary cardiorespiratory requirements during pregnancy. In such cases, medical therapy is not always sufficient to drive a heart, and open heart operation might be necessary. Many factors associated with cardiac operations requiring cardiopulmonary bypass, such as hypothermia, can adversely affect both the mother and the fetus, but the morbidity and mortality rates are higher for the fetus than the mother. Because fetal heart tones were lost during cardiopulmonary bypass and were reheard in the intensive care unit in our case presentation, we have presumed that the loss of fetal heart tones should not always indicate fetal death and have discussed harmful factors in relation with the fetal morbidity and mortality in light of the literature. (C) 2000 by The Society of Thoracic Surgeons.