INTRODUCTION: Mitral stenosis (MS) is recognized as one of the most common cardiovascular diseases during pregnancy and can result in adverse outcomes including maternal and fetal mortality if not diagnosed and treated in a timely manner. This study aimed to investigate the pregnancy outcomes of women with MS who were treated at the cardio-obstetric clinic in Alzahra Hospital, Isfahan, from 2011 to 2020. METHODS: A total of 81 pregnant women diagnosed with MS were selected for the study. Their demographic and clinical data, along with echocardiography information-including systolic pulmonary artery pressure (SPAP), severity of MS, and NYHA class-were monitored throughout pregnancy. Additionally, the maternal and fetal outcomes were examined. RESULTS: Among the participants, 38.3% were diagnosed with progressive MS, 56.8% exhibited severe stenosis, and 4.9% presented with very severe stenosis. Prior to pregnancy, no cases were classified as NYHA class 3 or 4. However, during the first trimester, six patients (7.4%) were classified as NYHA class 3. In the second trimester, 23 patients (28.4%) were in class 3, and 1 patient (1.2%) was classified as class 4. In the third trimester, 24 cases (29.6%) were in class 3, and 14 cases (17.3%) were in class 4. Notably, significant changes in NYHA class were observed throughout pregnancy (P <
0.001). Furthermore, 16% of participants required percutaneous balloon mitral commissurotomy, highlighting the severity of their condition. Additionally, 2.5% experienced decompensated heart failure and another 2.5% developed arrhythmia after delivery. Unfortunately, there was one case (1.2%) of mortality due to complications from MS. The study also documented one stillbirth (1.2%), 11 cases (13.6%) of spontaneous abortion, 17 cases (21%) of induced abortion, six cases (7.4%) of birth anomalies, three cases (3.7%) of prematurity, and four cases (4.9%) of intrauterine growth restriction, underscoring the critical need for careful management. CONCLUSION: The results of the study suggest that cardiac function in women diagnosed with MS typically declines during pregnancy. Furthermore, even with optimal treatments, certain complications may still arise.