This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Without breastfeeding the first menstrual flow usually begins --- weeks after delivery? \nSelect and explain. \nA. 2-4 weeks, B. 4-6 weeks, C. 6-8 weeks, D. 8-10 weeks', 'role': 'user'}, {'content': 'Answer: C \nExplanation: This is variable and depends upon whether the woman is lactating. Nonlactating mothers have an early resumption of menses by about 6-8 weeks. In nursing mothers, approximately 70% are amenorrheic until 4-6 months (refer pgno:424 Sheila 2 nd edition)', 'role': 'assistant'}]