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: Physiology
[{'content': 'The most common cause of the congenital heart defect is: \nSelect and explain. \nA. A viral infection in mother during first trimester, B. A bacterial infection in mother during first trimester, C. Consumption of NSAIDs by mother during first trimester, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Congenital heart disease is not uncommon, occurring in about 8 of every 1000 live births.\nOne of the most common causes of congenital heart defects is a viral infection in the mother during the first trimester of pregnancy, when the fetal heart is being formed.\nDefects are particularly prone to develop when the expectant mother contracts German measles; thus, obstetricians may advise termination of pregnancy, if German measles occurs in the first trimester.', 'role': 'assistant'}]