Pregnancy Dating Scan Accuracy: Understanding Ultrasound Timing

Question
I was wondering can an early dating scan done at 9 weeks be 5 weeks wrong?
Also would u help me by answering this I have had 5 ultrasound scans done over different times in my pregnancy my 1st was at 9w+1d, my 2nd 12w, My 3rd 15w+2d, my 4th 20w,my 5th 21+3d and my EDD is 18-04-2010 could I have possibly conceieved in early June? Thank u

Answer
Hi Ashleigh,

An ultrasound at 9 weeks isn't likely to be 5 weeks off.  If the April 4 date is confirmed with the first two ultrasounds, it's a solid date, and will not be off by 5 weeks.

If the ultrasounds are showing a due date of April 4, then you conceived towards the end of July, not the beginning of June.

I hope that helps!

Dorothy H, LCCE