Background: Open heart surgery during pregnancy is relatively rare at home and abroad, with high risk and high probability of maternal and infant death. How to carry out heart valve replacement under cardiopulmonary bypass (CPB) under the condition of ensuring the safety of mother and child is a focus of attention at home and abroad. Case introduction: We reported four cases of pregnant women who underwent cardiac surgeries under CPB during pregnancy in our hospital. Three cases had infective endocarditis (IE), who underwent heart valve placement with mechanical mitral valve, and one case with ascending aortic aneurysm underwent Bentall surgery. The operations of four cases were successful, and further follow-up evaluation of the pregnant women and fetus showed no abnormality. Patients' details are available in the following table. Conclusion: Actively and proactively for heart disease during pregnancy with obvious symptoms. Cardiac valve replacement under CPB will be the first choice, and this may become the primary surgical treatment for symptomatic heart diseases during pregnancy.