THe earlier they are, the less accurate they are
I went through the same thing you went through. Wait till the u/s at 12 weeks
Thanks ladies for your answers I'm happy dont matter if baby comes late or early :)
I don't think they r accurate before 12 weeks. Because of previous m/c and bleeding I got a scan at 6wks which said I was 4+wks, a scan at 7wks that said 6wks, scan at 9wks that said 7wks and a scan at 10wks that said 8wks!!! Yet at my 13wk scan I dated exactly 13wks!! Then another scan at 20wks which was bang in my original dates. When I asked the Dr/midwife why for the 1st lot of scans I measured small and they told me it's because the baby is so tiny it's really hard to say a definite date so early
Ultrasounds done in the first trimester are the most accurate in dating the age of your baby, though it is not perfect not all babies are the exact same size or develop at the same rate, but this early on there is less variation between babies and supposedly should be accurate within 3-4 days. There is a small possibility they made an error, generally they determine the age by measuring the length from crown to rump or the size of the sac.
The ultrasound I had done at 8 and a half weeks was spot on for my twins, measuring them at 8wk, 3d and 8wks, 4d, which was percisely the length of time since my lmp.
From what I've been told ultrasounds before week 9 are extremely accurate :) Mine was able to go to the day baby was conceived at 8 weeks. I think it helped bc I knew when he ought oh'd :P best ought oh of my life :D
The first 13 weeks is the most accurate for dating by ultrasound. Most likely you ovulated later then you thought.
I believe the earlier on in first trimester , the more accurate the dating scan is .