This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Obstetrics, Subject name: Social & Preventive Medicine
Which of the following is not true about expected date of delivery (EDD)? 
Select and explain. 
A. Less than 5% deliver on the expected date of delivery, B. 50% deliver within one week, C. 80% deliver within two weeks, D. Standard deviation around EDD is 3 weeks
D: Standard deviation around EDD is 3 weeks
Answer: D: Standard deviation around EDD is 3 weeks 
Explanation: Ans. d. Standard deviation around EDD is 3 weeks (Ref Dutta's (Jaypee) / 73)Expected Date of Delivery (EDD)Only 4% of births take place on EDDAbout 50% deliver within 1 week on either side of EDD80% deliver about 2 weeks before to 1 week after EDDStandard deviation is of 13 days(90% of babies will be born within three weeks of their EDD. and 21% will be born within three days of it)