PLE-5950

A 42-year-old woman, gravida 2, para 2, comes to the physician because of a 3-month history of swelling of her legs and mild abdominal pain and bloating. Abdominal examination shows no abnormalities. Rectovaginal examination shows fullness in the right adnexa. Transvaginal ultrasonography shows an irregular mass in the right ovary with some solid components to a predominantly cystic lesion. Her serum CA 125 level is 120 U/mL (N<35). What treatment is most likely to have prevented this patient's symptoms?