Which of the following is not true about expected date of delivery (EDD)?

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)