How accurate are early scans?

[Mailys]

I went for an early scan after having some bleeding. When I went, according to my dates I was six weeks & four days. The sonographer confirmed that baby had a heartbeat and everything was in the right place but said she thought I must be 5 weeks & six days. I'm just confused as I'm pretty sure of my dates and I took my pregnancy test a good two weeks before the scan so I must have only been 3 weeks. Surprised a test will pick up a postive that early?

I'm just wondering if anyone else has had similar but at the dating scan at 12 weeks it's been confirmed to be closer to their dates?

They date from the first day of your last period, not from the date you conceived.

Most accurate time is 11-13weeks, early ones can be easily out by a good few days. Don’t get bogged down in your dates as embryos develop at different rates, our cycles are all different

When it’s so early 1/2mm can make a big difference in dates. The presence of a heartbeat is a promising sign 😊

When I was 7+5 I had an early scan who said I was 6+6. I just continued to go off my original dates and when I went for 12 week scan at 12+6 I was 12+3. So chances are when you go for your 12 week scan they’ll move it again so don’t worry . Unless you have a 28 day cycle and ovulate day 14 then your dates going off LMP won’t be 100% 😊

Heartbeat is positive - I’m not sure why the dates matter? It’s an estimate from your last period, and at 12 week scan they can do more accurate measurements and dating

Thanks all for your replies. Will just wait now until the proper dating scan.