Results 
Overall, 350 children were identified. Eighteen patients (5%) presented with a synchronous bilateral form at diagnosis. Surgery was performed by laparotomy (85%) and laparoscopy (15%). OSS and TO were performed in 59% and 41% of cases respectively. Perioperative tumor rupture occurred in 23 cases, independently of the surgical approach. Twenty-nine second events occurred (8.3%) in a median time of 30.5 months from diagnosis (ipsilateral: 8 cases including one malignant tumor, contralateral: 18 cases, both ovaries: 3 cases). A large palpable mass, bilateral forms at diagnosis and perioperative rupture had a statistical impact on the risk of second event, whereas type of surgery or approach did not.