Highest mortality in pregnancy-
Eisenmenger syndrome
Fallot's tetrologv
Coarctation of aorta
Marfan’s syndrome
Eisenmenger syndrome 

These patients have pulmonary hypertension with shunt (right to left) through an open ductus or ASD or VSD. Maternal mortality is high i.e. 50% & so is a perinatal loss (50%).
Fallot’s tetralogy, cocoarctationf aorta & Marfan's syndrome hav mortality’ rate of 5-10%, 3-9% & 25% respectively.