Most common hea disease which is associated with maximum moality during pregnancy is:

Eisenmenger's syndrome is the reversal of a left to right shunt (ASD, VSD, PDA) due to progressive pulmonary hypeension. Maternal moality approaches 30-50% and fetal loss may be as high as 75%. It is one of the few conditions in which pregnancy is contraindicated. Women with Eisenmenger syndrome tolerate hypotension poorly, and the cause of death usually is right ventricular failure with cardiogenic shock. VSD is generally well tolerated during pregnancy. Patients with aoic insufficiency tolerate pregnancy well because the fall in peripheral resistances ors forward blood flow and decreases the regurgitant fraction. Mitral regurgitation is also generally well tolerated in pregnancy. Ref: Hameed A.B., Montoro M.N. (2013). Chapter 27. Cardiac & Pulmonary Disorders in Pregnancy. In DeCherney A.H., Nathan L, Laufer N, Roman A.S. (Eds),CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.