The association of an ovarian cyst with pregnancy is relatively rare; it may result in serious maternal and fetal complications and its treatment is still controversial. We present a case in which the rarity is given by the association of an 11cm--serous right ovarian cyst (with signs of torsion) with a monofetal 6 gestation week--pregnancy, by the initial conservative management and by the subsequent laparotomy and cystectomy at 16 gestational weeks, required by the acute abdominal pain caused by the torted cyst. The approach was initially conservative followed by laparotomy and cystectomy at 16 gestation weeks, required by the acute abdominal pain caused by the torsive cyst. Pregnancy was, afterwards, uneventful and the patient delivered vaginally, at term, a 3200 g healthy girl. Management options of such a case are discussed.