With the development of fetal ultrasonography, detection of fetal ovarian cysts has been increased. Although ovarian cyst formation during the perinatal period is a self limiting process, there is still considerable controversy regarding the best treatment of the fetal ovarian cyst. The purpose of this study is to evaluate the natural history of fetal ovarian cysts and to analyze the result of treatment. From 1995 to 2004, 31 consecutive fetuses with ovarian cysts were followed by ultrasonography during the perinatal period. The fetal ovarian cyst was diagnosed by prenatal ultrasonography between 25weeks and 38 weeks and the mean size of the cysts was 5cm (ranged from 2 to 8cm). At birth, 3 cysts disappeared. In 2 cases, the diagnoses were changed to multicystic kidney disease and intestinal duplication. During following up of 26 cysts, 15 cysts have resolved completely. Seven cysts required oophorectomy because of cyst torsion (n=3), differentiation of tumorous condition (n=2), increased size of cyst (n=1), and large size (8cm) of cyst at birth (n=1). Fetal ovarian cyst should primarily be observed, and only in the limited cases, surgical treatment would be required for the risk of complications such as torsion and differentiation from benign to malignant pathology.

Among 60 children with teratoma, forty-three (71.7 percent) were girls and 17 (28.3 percent) boys. Primary sites were sacrococcygeal in 30 patients (50 percent), retroperitoneal in 12 (20 percent), ovarian in 11 (18.3 percent), testicular in 3 (5 percent), and one in each of nasopharyngeal, gastric, hepatic and pancreatic (1.6 percent, respectively). Fifty-five (91.7 percent) teratomas were benign and 5 (8.3 percent) malignant. Malignant teratomas were detected only at sacrococcygeal region (16.7 percent). Older than 2 months of age at diagnosis, presence of urinary and colonic obstructive symptoms, multiple masses and elevated serum alpha-fetoprotein were indicators of malignancy in sacrococcygeal region. Tumor size, presence of calcification, and gross appearance (cystic or solid) did not correlate with malignant nature. Thirteen (21.7 percent) cases were associated with other anomalies. For the immature teratoma, the operative resection without adjuvant chemotherapy was enough. Three malignant cases were survived, one with chemotheapy for 3 years and the others without chemotherapy for 5 and 10 years.