Talk to me about dates

[HarkAtYou]

I'm a bit unsure of how far along I am and hoped that someone might be able to advise.
My last period was on 2nd or 3rd July which would make me 9+4 I think, however I've had two early scans. The first on 16th August showed no heartbeat so I went back on 27th August and saw a heartbeat and was told I was measuring 7+3 on one image and 6+4 on another.
My midwife says that ultrasounds can be a week out but it this likely since the heartbeat developed between the two?
I know that they'll date me at my 12 week scan but is it still inaccurate then?
Has anyone had a similar experience?
TIA

I'd make you just under 10 weeks as well.

With DS2, I had a scan at (my dates) 6+2, 8+2, and around 13.

First scan was no heartbeat, aprox 5 weeks. 2 weeks later they put me at 6+1. I questioned 1 weeks development in 2 weeks.
At my dating scan, I was given an edd where I though it was around, and he arrived on his edd.

When they are that little, a fraction of a mm out makes a big difference - and remember they are measuring through all your skin and muscle (and in my case fat)

A heart beat is a fab marker - the rate of miscarriage following a visible hb is much reduced.

Remember the date from your dating scan is just an estimated, and you can reasonably be 2 weeks either way without anyone worrying about it.

Congrats on your pregnancy.

Oh thank you for your reply, that's good to know about being 2 weeks out.
I really hope I'm more like 10 and I'll take just 2 more weeks of sickness if you please?!