Mitral stenosis (MS) encountered in women of childbearing age is nearly always rheumatic in origin. Maternal and perinatal complications during pregnancy in women with MS reflect the unfavorable interaction between the normal cardiovascular changes of pregnancy and the stenotic mitral valve. (See "Maternal cardiovascular and hemodynamic adaptations to pregnancy".)
This topic will review the evaluation and management of women with mitral stenosis during pregnancy. Management of other types of heart disease during pregnancy, including those with MS who have undergone valve replacement, is discussed separately. (See "Acquired heart disease and pregnancy" and "Pregnancy in women with congenital heart disease: Specific lesions" and "Pregnancy in women with congenital heart disease: General principles" and "Management of pregnant women with prosthetic heart valves".)
Prevalence — Women with heart disease comprise approximately 1 percent of the obstetric population seen in large volume centers in developed countries. In the United States and Canada, women with rheumatic heart disease, of which MS is the most common manifestation, comprise <25 percent of the pregnant women with heart disease [1,2]. In contrast, MS is a common condition in pregnant women with heart disease in other areas of the world where rheumatic heart disease is prevalent. For example, rheumatic heart disease was the underlying cause in 56 to 88 percent of women in three studies from centers from Brazil, Turkey, and Senegal reporting on a total of 1194 pregnancies in women with heart disease [3-5]. (See "Natural history, screening, and management of rheumatic heart disease", section on 'Mitral stenosis'.)
IMPACT OF CARDIOVASCULAR CHANGES IN PREGNANCY IN WOMEN WITH MITRAL STENOSIS
In mitral stenosis (MS), the stenotic mitral valve restricts diastolic left ventricular filling, resulting in an elevated transmitral gradient and left atrial pressure that are further increased by the physiologic hypervolemia and increased heart rate during pregnancy, thereby increasing the risk of pulmonary congestion or pulmonary edema. The risk of pulmonary congestion remains during labor and delivery, as a result of uterine contraction during labor, and with the autotransfusion of venous return from the lower extremities as the emptied uterus is no longer impeding venous return. Increased atrial irritability and hypercoagulability associated with pregnancy, when combined with increased left atrial pressure, increase the risk of atrial fibrillation and left atrial thrombus formation. (See "Maternal cardiovascular and hemodynamic adaptations to pregnancy" and "Deep vein thrombosis in pregnancy: Epidemiology, pathogenesis, and diagnosis".)
RELATIONSHIP BETWEEN SEVERITY OF MS AND IMPACT OF PREGNANCY
There is a direct relationship between the severity of mitral stenosis (MS) and the risk of maternal and/or fetal complications [6-8]. (See "Natural history of mitral stenosis" and "Echocardiographic evaluation of the mitral valve".) There is an incremental increase in the frequency of maternal and fetal complications with increasing severity of MS (table 1). While those with moderate or severe stenosis represent the higher risk group, elevated event rates are seen in those with even mild MS, reflecting the effects of the 30 to 50 percent increase in cardiac output superimposed on a mildly stenotic valve . History of cardiac complications (including pulmonary edema, arrhythmias, transient ischemic attacks, or stroke) prior to pregnancy and poor baseline maternal functional class are additional risk factors for maternal cardiac complications during pregnancy [1,8]. In the presence of obstetric risk factors (including extremes of maternal age, smoking), the presence of maternal MS confers a risk of perinatal complications .