I n t r o d u c t i o n: Hypoplastic left heart syndrome (HLHS) is a congenital heart anomaly that is diagnosed prenatally or postnatally. The prenatal diagnosis leads to limiting the rate of systemic complications in the preoperative period due to optimization of the early therapeutic management. O b j e c t i v e: The objective of the study is to determine the effect of prenatal diagnostic management of HLHS on the condition of newborns and the frequency of antibiotherapy employment prior to the first stage of surgical treatment. Me t h o d o l o g y: The study included 95 children with HLHS operated on in the years 2014–2016. The cohort was divided into two groups: newborns with a prenatally diagnosed heart defect (50 children — 52.6%) and neonates with the defect diagnosed after birth (45 children — 47.4%). The data of the patients were analyzed based on their medical records. R e s u l t s: The mean age of the children upon admission was 3.86 days in the group of patients with the prenatally diagnosed heart defect (PreHLHS) and 7.41 days in the group of newborns without the prenatal diagnosis (PostHLHS) (p = 0.001). In 60% of the PreHLHS group patients (30/50), at least one antibiotic was administered, while in the PostHLHS group, antibiotherapy was employed in 93.3% (42/45) cases (p = 0.001). Bacteriological tests demonstrated pathogen growth in 33 children (36% and 33.3%, respectively), what accounted for 34.7% of the entire cohort. On the average, the first antibiotic was introduced on the 6.55th day of life in the PreHLHS group and on the 2.73th day in the PostHLHS group (p = 0.005). Th e most profound differences in antibiotic employment involved aminoglycosides. The aforementioned type of antibiotic medications was administered to 6% of the children with the prenatal diagnosis and to 17.8% of the children diagnosed postnatally (p = 0.042). C o n c l u s i o n s: Preoperative antibiotherapy in children with HLHS was employed more frequently than it would be indicated by microbiology tests results. Antibiotics were observed to be introduced more commonly and earlier in the newborns with the postnatally diagnosed congenital heart defect.