Most pregnancies last around 40 weeks (or 38 weeks from conception), so typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period (LMP). Another way to do it is to subtract three months from the first day of your last period and add seven days.

What is the formula for calculating EDD?

The rule estimates the expected date of delivery (EDD) by adding a year, subtracting three months, and adding seven days to the origin of gestational age. The result is approximately 280 days (40 weeks) from the start of the last menstrual period.

What is the best way to predict fetal weight?

The most established way to estimate fetal weight is the ultrasound method, as previously described [10,11,12] and most commonly performed with three measurements fitted into an algorithm designed by Hadlock et al. [10].