Progressive pulmonary stenosis in the fetus: two case reports.

Fetal echocardiography is a helpful tool in diagnosing and following the natural history of fetuses with congenital heart disease. This report describes two fetuses with complex congenital heart disease that developed progressive pulmonary stenosis in utero. On fetal echocardiogram, one of the fetuses had tetralogy of Fallot and the other had a single ventricle. Both fetuses, when followed serially by fetal echocardiography, showed pulmonary stenosis that progressed in severity. These findings confirm that certain cardiac defects progress in severity in utero.