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a method for calculating the estimated (or expected) date of confinement (EDC) or of delivery (EDD): count back three months from the first day of the last menstrual period, and then add one year and seven days. An unavoidable error of plus or minus two weeks may occur.
Etymology: Franz K. Nägele, German obstetrician, 1778-1851; L, regula, model
a method for calculating the estimated date of delivery based on a mean length of gestation. Three months are subtracted from the first day of the last normal menstrual period, and 1 year plus 7 days are added to that date.