conception dates and ultrasounds

[sparklingreactions]

how accurate are early ultrasounds could an 8 week ultrasound have possibly been an 11 week ultrasound even if i had a period inbetween these 2 dates? i had another 2 scans following this scan an they all tied in to within 5 days can i trust this?

[sparklingreactions]

also due dates count back almost exactly 38 weeks to when i think i concieved

[littlemissm]

Ultrasounds are pretty good can be out up2 a week any more & i think they would know.Pregnancy is actually 38wks not 40 so you are right saying 38 wks from conception but they add on 2 weeks so if you take it from the 1st day of your period .When you find out you are pregnant ussually when you should be due on you are said to be 4 or five wks (in my case i always find out at 4 wks) but actually you are only 2/3 wks pregnant because when they take it frm the 1st day of your lmp you are not actually pregnant yoy dont usually concieve till about 2wks after this. So 2wks have been added on hope this make sense.