Doctor’s Guide -- PHILADELPHIA, Pa -- October 26, 2010 -- When prenatal diagnosis detects the severe heart defect hypoplastic left heart syndrome (HLHS) in a fetus, a comprehensive prenatal evaluation is important to provide parents an accurate prognosis. In HLHS, one of the heart’s pumping chambers is severely underdeveloped. However, say researchers, in two-thirds of cases, reconstructive surgery affords the infant an excellent chance of early survival.