EXPECTED DATE OF CONFINEMENT [EDC]
The EDC , or estimated date of delivery, cannot be precisely stated. It has become traditional to calculate the EDC from Nagele’s rule:
Add 7 days to the first day of the last menstrual period [LMP]; subtract 3 months; add one year. EDC = [LMP + 7 days]- 3 months + 1 year].
For example, if the first day of the LMP was June 4, 2008, the EDC will be: [date 4+7=11 ] [months 6-3 =3 ] [years 2008+1=2009] =
11 03 2009 or EDC is March 11 2009.
Nagele’s rule is based on a 28-days menstrual cycle, with the expectation that ovulation occurred on 14th day. The pregnancy in women lasts about 10 lunar months or 40 weeks or 280 days.
Only 4 % of patients will deliver on the EDC after a spontaneous labor. Almost pregnancies will deliver during the period extending from
2 weeks before through 2 weeks after the EDC.