This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abnormal labor, Subject name: Anatomy
[{'content': 'In a patient with history of previous still bih, optimum time of delivery is : \nSelect and explain. \nA. 37 weeks, B. 38 weeks, C. 39 weeks, D. 40 weeks', 'role': 'user'}, {'content': 'Answer: C \nExplanation: All the females who have previous H/o still bih, the optimum time of delivery is 39 weeks and the mode of delivery is vaginal delivery. Ref: Williams Obs 25e pg 649.', 'role': 'assistant'}]