We encountered a case of Stage Ic ovarian serous borderline malignancy in the first trimester of pregnancy. At laparotomy, spontaneous rupture of the capsule and a small amount of serous ascites was observed. Because of the laparotomy during pregnancy, correct staging of the tumor might not be performed. This case presented a major problem in deciding the treatment strategy, which are reported here together with some discussion of the literature on the preservation of fertility in borderline ovarian malignancy.