You can yourself predict the due date of your child's birth, if you remember the first date of your last menstrual period. Formula for calculating the expected date of delivery, i.e, EDD is based on the knowledge of the duration of pregnancy.
Duration Of Pregnancy
Duration of pregnancy calculated from the first day of the last menstrual period is known as the menstrual age or gestational age, which is equal to:
- 10 lunar months
- 9 calendar months and 7 days
- 280 days
- 40 weeks
Formula To Calculate The Due Date
Expected date of delivery, also called Expected date of confinement (EDC), can be calculated using the Nagele's rule or formula.
What is Nagele's Formula?
Using nagele's rule, expected date of delivery is calculated by subtracting 3 months from the month of the last menstrual period, and adding 7 days to the first day of the last menstrual period. Thus:
Month of EDD = Month of LMP - 3
Day of EDD = First day of LMP + 7
P.S. - EDD is the expected date of delivery and LMP is the last menstrual period.
For Example:
If your LMP = 12 June 2011
Using Nagele's rule
- Month of your EDD = 6 (June is the 6th month of the year) - 3
= 3 i.e. third month of the year, which is March
- Day of your EDD = 12 + 7 = 19
So, if 12 June 2011 is your first day of the last menstrual period-
Your Due Date = 19 March 2012
Accuracy of prediction of due date using Nagele's formula
About 50% women deliver in the range of EDD calculated with this method +/- 7 days.
