This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': "Which of the following type of ovarian tumor most frequently cause complications during pregnancy ? \nSelect and explain. \nA. Teratoma, B. Mucinous cystadenoma, C. Serous cystadenocarcinoma, D. Brenner's tumor", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Complications associated with mature cystic teratoma are torsion, rupture, infection, hemolytic anemia and development of malignancy. Torsion and rupture of teratoma are more likely to occur during pregnancy.', 'role': 'assistant'}]