This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Gynaecology & Obstetrics
[{'content': 'What is the clinical diagnosis when a pregnant woman presents with bloody vaginal discharge through a closed cervical os during the first 20 weeks? \nSelect and explain. \nA. Threatened aboion, B. Complete aboion, C. Incomplete aboion, D. Preterm labor', 'role': 'user'}, {'content': "Answer: A \nExplanation: The clinical diagnosis of threatened aboion is presumed when bloody vaginal discharge or bleeding appears through a closed cervical os during the first 20 weeks (Ref: William's Obstetrics; 25th edition)", 'role': 'assistant'}]