Estimated due date (EDD) confusion

Dear all,

I had an ultrasound scan today on 28th Jan, 2016.

My last period starting date is 21st Nov, 2015. So, accordingly my EDD would be around 27-29 Aug, 2016.

In the scanning report today, the SCAM LMP is mentioned as 8th Nov 2016 and EDD as 15th Aug, 2016.

Can you please let me know if my actual LMP is 21st Nov, how come it is given as 8th Nov scanning report? Is this normal/usual or do I need to check it with another doctor?

With regards,

Ramya – to be mom

Dear ramyaphani,

There exist two ways of calculating your estimated due date (EDD): on the one hand, as you did, by calculating your last menstrual period (LMP) plus 40 weeks; on the other hand, as your doctor did, from the date of the first ultrasound scan onwards.

Women with irregular menstrual cycles are unable to know which is the exact date in which fertilization took place. In these cases, calculating your EDD according to the scanning report of your first trimester is more accurate, since it is estimated on the basis of fetus growth measurements.

To sum up, the results your doctor gave you are totally right: he/she has measured them according to the parameters shown through ultrasound scan, in which case the results are not always the same as those you obtain by calculating from the date of your LMP.

The following article may be of interest: Pregnancy due date calculator.

I hope I have clarified all your concerns,

Regards