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
Uterus is receptive for implantation for how many days after feilization - 
Select and explain. 
A. 6 days, B. 12 days, C. 6 weeks, D. 12 weeks
D: 12 weeks
Answer: D: 12 weeks 
Explanation: Superfetation is the feilization of two ova released in two different menstrual cycles. The nidation and development of one fetus over another fetus is theoretically possible until the decidual space is obliterated by 12 weeks of pregnancy. Ref : Dutta book of obstetrics 8th Ed