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
Which of the following type of ovarian tumor most frequently cause complications during pregnancy ? 
Select and explain. 
A. Teratoma, B. Mucinous cystadenoma, C. Serous cystadenocarcinoma, D. Brenner's tumor
A: Teratoma
Answer: A: Teratoma 
Explanation: 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.