I have been asked this question by many of my patients. After each scan, the couple are excited to know what is the expected delivery date. Mentioned as EDD in the scan report. This is because of the misconception that the delivery date changes with each scan. This is not correct.

To understand why is not correct. There are some basic things that you need to understand.

1. Baby (I am referring to the fetus) takes 9 months and 7 days to grow inside the womb before it matures. This is equal to 280 days or 40 weeks.
2. Expected delivery date is calculated based on the last menstrual periods (written as LMP on your scan or medical records).
3. To summarise, add 280 days to your Last Menstrual period (LMP); you get your Expected delivery date (EDD).

Only exception is when the periods are not regular. This means to say that the gap between the 2 periods is less than 21 days or more than 35 days. In this scenario, we will  give the expected delivery date based on the early pregnancy scan (done between 6-10 weeks). This will be recorded in the scan as Corrected- EDD or CEDD. Any correction of EDD should be done only before 13 weeks of gestation (that is during dating scan or NT scan.)

Now, that we know the baby needs 40 weeks to mature. The next question that comes to the mind of anyone is “So the delivery always takes place at 40 weeks?”.

The answer is a simple NO.

Then why are the stressing so much on EDD; Corrected EDD and so on. Fun fact is that only 4% of the pregnant women delivery exactly at 40 weeks of their pregnancy.

When we meant the baby matures at 40 weeks. It does refer to all the organ system of the body. But what is the most important thing is for the baby’s lungs to mature. A matured-developed lungs will ensure that the baby can sustain its life outside the womb. Between 37 weeks to 40 weeks, the baby’s lungs are matured enough to sustain life independently.

Ensuring a proper EDD, will help the doctors to identify the pregnant women who are delivering earlier than 37 weeks. These babies will require additional treatment and need to be kept under close supervision.

Additionally, dating the pregnancy will help in planning specialized scan such as NT scan, anomaly scan and a proper fetal growth monitoring. Also, there are other medications, that need to be given within a specific time period.

Disclaimer:- This information is for awareness and education purpose only. Always, discuss the reports with your doctor after the scan.

Have a bright day.