Purpose: To determine the natural history of fetal ovarian cysts and to investigate whether the prognosis can be predicted by prenatal ultrasonography (US).Methods: This retrospective study includes cases of fetal ovarian cysts diagnosed by prenatal US over a 6-year period. Cases were divided into four subgroups of cysts (small and simple, small and complex, large and simple, large and complex) according to their size and echotexture. US examinations were repeated every 2 weeks from the time of diagnosis to treatment.Results: A total of 37 cases were included in the study. 32.4% of the cases regressed spontaneously in the prenatal period and 32.4% did so in the infantile period. Prenatal resolution occurred more frequently with small cysts than with large cysts (p = 0.03). Neonates with complex cysts required surgical treatment more often than neonates with simple cysts (p = 0.009). 27.0% of the cases underwent surgery due to ovarian torsion. The torsion rate of fetal ovarian cysts that progressed in the prenatal period was significantly higher than in the case of stable cysts (p = 0.001). Conclusion:The size of the fetal ovarian cysts, their US appearance and the progression of the cysts during follow-up are the main determinants of the neonatal outcome.