Objective. To study possibilities for using current methods for intrauterine surgery for severe congenital heart diseases. Subject and methods. The paper describes a case of a 36-year-old diabetic gravida II with diabetes mellitus, who has undergone fetal cardiac ultrasonography at 20 weeks’ gestation, which diagnosed endocardial fibroelastosis of the left ventricle, its dilation with diminished systolic function, critical aortic valve stenosis, and mitral valve insufficiency. Fetal left heart hypoplasia developed at 27—28 weeks’ gestation. Results. Intrauterine valvuloplasty of the oval window was performed under constant ultrasound guidance at 30 weeks’ gestation. The patient delivered at 34—35 weeks, as obstetrically indicated, to a live-born boy (birth weight, 2090 g; height, 43 cm; and Apgar score, 6—7). He was observed and treated at children’s hospital for 10 days. At the age of 11 days, the newborn baby died from decompensated cardiovascular performance. Conclusion. To create a fetal atrial septal defect in fetuses with severe heart diseases leading to hypoplastic left heart syndrome prevents worse health in such neonatal infants immediately after birth and allows for preoperatively preparing for aortic valvuloplasty.