Mucinous cystadenomas of the ovary are benign epithelial neoplasms that can grow rapidly during pregnancy. They may cause ovarian torsion, virilization, inferior vena cava syndrome, and even preterm labor and fetal growth restriction. Various theories exist regarding the pathogenesis of these tumors. One hypothesis suggests that they may arise from teratomas. Our case report describes synchronous mucinous cystadenomas and ovarian teratomas, as well as metachronous mucinous cystadenomas in patients with a history of ovarian teratoma. There has been no report of metachronous ipsilateral teratoma after previous mucinous cystadenoma. We present a 22-year-old female with a history of bilateral ovarian tumors in a prior pregnancy noted to have a recurrent ovarian mass on her left ovary at the time of cesarean section of a subsequent pregnancy. She had two prior cystectomies for metachronous mucinous cystadenomas of her left ovary, and a right salpingo-oophorectomy for the ovarian torsion in her previous pregnancy. On her current pregnancy, she developed a mature cystic teratoma of the remaining left ovary. The rapid growth and recurrence rate of these tumors highlights the importance of close surveillance of ovarian masses during pregnancy, even those that seem benign. In this case, a history of unilateral salpingo-oophorectomy with multiple contralateral cystectomies did not appear to affect her fertility. Her future ovarian reserve is unknown, pointing to the need for adequate pre-operative counseling in similar cases of ovarian masses in pregnancy.