My first question to the doctor on knowing that I was expecting was "Doc, when is the expected date of delivery?" EDD as is known is calculated from the first day of your LMP (Last menstrual period). it works out to roughly 39 weeks + 9 days. Ofcourse, give and take a few days based on what your sonography reveals. The way my gynaecs calculate how old the foetus is has always made me think that docs are not good at math. While she maintained for the first 4 months that my EDD was 24th Dec, it suddenly changed to 27th Dec mid way. This article in Hindu titled Post-term pregnancy — a dilemma revealed their easy mathematical aptitude :)

The due date
The average length of pregnancy is 280 days, or 40 weeks from the first day of a woman's last menstrual period. It can be hard to predict the exact date of delivery. Only 5 per cent of babies are born on their due dates. Calculating the due date helps the obstetrician know which month of pregnancy you are in and to monitor the progress of the baby, particularly its growth.

Women with irregular periods may require an ultrasound in early pregnancy to establish the actual due date.

Even women with very regular periods may be asked to have an ultrasound scan in early pregnancy to confirm the age of a fetus and thereby, the due date.

The due date should be confirmed as early in pregnancy as possible. Later, it becomes harder to set the due date accurately.

Calculating the due date

The due date is based on the assumption that the conception occurred exactly 2 weeks after the first day of the last period. The method used by all obstetricians around the world, is to add 7 days and subtract 3 months from the date of the first day of the last menstrual period. For example, if the last menstrual period began on June 1, 2006, the due date is calculated as follows: June 1 + 7 days = June 8. June 8 minus 3 months = January 8. Therefore the estimated due date would be January 8, 2007.

Tags: , , ,