Abstract Background: HLHS (hypoplastic left heart syndrome) is a serious congenital heart defect. In neonates with congenital heart disease HLHS accounts for nearly 25% of neonatal deaths. The etiology of HLHS is unknown. At present we expect to have those cases diagnosed in the second trimester of pregnancy. Aim: The main aim was to find the rate and outcome of the congenital heart defect – left heart hypoplasia (HLHS). Material and methods: All cases of this heart defect found in the High Risk Pregnancy Clinic in 2001-2007 were presented. Twice the congenital malformation was diagnosed after delivery and once during pregnancy - in the second trimester. All babies were delivered between 38 and 39 weeks of pregnancy, one by the spontaneous normal delivery, one by elective caesarean section and one by emergency caesarean section because of fetal distress during the delivery. All of the newborns were transported to the Pediatric Cardio surgery Unit of M.U. and operated in first weeks after delivery. Results: In two cases the operation was complicated and children died due to the cardiac arrest. One of the babies died before surgical correction. Two of the women, whose babies died after the operation gave birth to healthy newborns with no cardiac abnormalities. Conclusion: The HLHS is the most serious heart congenital malformation diagnosed often after the delivery because of lack of sufficient diagnostic system in healthy women. The prognosis for the children is bad, but the chance of giving birth to healthy children in the future is good.