Abstract The main criteria for establishing fetal ovarian cysts prognosis are their diameter and echogenicity. The choice of management in case of fetal ovarian cyst remains controversial. In the following article we have reported a case of a fetal ovarian cyst with detailed fetal echocardiography before and after prenatal aspiration. The fetus at 35 weeks of gestation presented with an ovarian cyst of 70mm in diameter and normal heart anatomy and size. However, detailed fetal echocardiography revealed functional abnormalities such as: monophasic inflow pattern of tricuspid valve, holosystolic tricuspid regurgitation and pericardial effusion. Two days after prenatal aspiration of the cyst, the functional abnormalities in fetal echocardiography receded. After prenatal aspiration we observed a residual cyst of 15mm in maximal diameter. The delivery was spontaneous at 36th week of pregnancy and the infant was discharged from Neonatology Dept on the sixth day of postnatal life. The cyst regressed spontaneously in the course of the next two months. This is the first report when detailed fetal echocardiography revealed hemodynamic improvement after prenatal aspiration of a fetal ovarian cyst which may mean that huge fetal ovarian cysts might complicate fetal heart function.