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Objectives: To describe ultrasound features of fetal ovarian cysts as reported by the original ultrasound examiner, to apply International Ovarian Tumor Analysis (IOTA) terminology after retrospective analysis of the images and to describe patient management and evolution of fetal cysts during pregnancy and after delivery. Methods: This retrospective observational study included pregnant women diagnosed on ultrasound examination with a fetal ovarian cyst at the Prenatal Diagnosis Division of the Bambino Gesù Children's Hospital, in Rome, between March 2011 and May 2020. Cysts were classified by the original ultrasound examiner as 'simple' (unilocular anechoic cyst) or 'complex' (cyst with other morphology). In addition, three ultrasound examiners, experienced in gynecologic ultrasound, classified retrospectively the fetal ovarian cysts according to IOTA terminology, by reviewing stored ultrasound images. The evolution of these fetal ovarian cysts during pregnancy and after birth was recorded. Results: Included were 51 ovarian cysts in 48 fetuses. Of the 51 cysts, 29 (56.9%) had been classified by the original ultrasound examiner as 'simple', and 22 (43.1%) as 'complex'. Of the simple cysts, the majority (20/29 (69.0%)) resolved spontaneously after delivery, 2/29 (6.9%) resolved following intrauterine aspiration, 2/29 (6.9%) resolved after postnatal aspiration and 5/29 (17.2%) underwent surgery due to persistence after delivery; in all five, normal ovarian parenchyma without signs of necrosis was observed at histology. Of the complex cysts, 7/22 (31.8%) resolved spontaneously. The other 15/22 (68.2%) were removed surgically and, at histology, necrosis was observed in most (12/15 (80.0%)), while a benign epithelial cyst with normal ovarian parenchyma was observed in 3/15 (20%). After reviewing the ultrasound images and applying IOTA terminology, all 51 (100%) fetal cysts were described as unilocular; 29/51 (56.9%) cysts showed anechoic content (described as simple cysts by the original ultrasound examiner), and 10/51 (19.6%) had low‐level, 1/51 (2.0%) had ground‐glass, 9/51 (17.6%) had hemorrhagic, 1/51 (2.0%) had mixed and 1/51 (2.0%) had undefined content (all described as complex by the original ultrasound examiner). Among the 29 anechoic ovarian cysts, resolution was observed in most (24/29, 82.8%) cases. Similarly, resolution was observed in 7/10 (70.0%) cysts with low‐level content. Resolution was not observed in any of the other 12 cysts and all of these cases underwent surgery, with evidence of necrosis being observed in 11 (91.7%). Conclusions: Applying IOTA terminology provided a more detailed and accurate description of fetal ovarian cysts compared with the original classification into 'simple' and 'complex' categories. Anechoic cysts (described as simple cysts by the original ultrasound examiner) and cysts with low‐level content (described as complex by the original ultrasound examiner) frequently resolved spontaneously. Cysts with ground‐glass, hemorrhagic, mixed or undefined content were frequently associated with necrosis at histology following surgery. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]