EDC is the abbreviation often used to indicate the "estimated date of confinement" in pregnancy. This is the date when child birth is most likely to take place. Many tables and charts are available to obtain the EDC. Nagele's rule is a mathematical formula to obtain the EDC assuming a normal 28-day cycle of menstruation: to obtain the month of EDC, subtract 3 from the month of the last normal menstrual period to obtain the day of EDC, add 7 to the first day of the last normal menstrual period