Accuracy of early dating scans and due dates?

[Sarahjane282828]

Hi,

So unexpected but very happy mamma here needing some advice. How early are transvaginal scans at dating at weeks 4,5,6??

basically I am (was) in an open relationship on contraception but found myself pregnant. At 32 I feel happy with this but want some further clarity for peace of mind :)

very early.. only 6 weeks now according to scans. Basically I had sex with a man on 17th July, came on period on 26th July. He did not do the deed inside me.

Period ended on 31th July and only slept with partner since. Had a negative pregnancy test on 16th Aug but then faint positive by 21st. I’ve had one scan a week since finding out (found out at 3w 4d) due to my health complications, all have dated me less than 6 weeks now. Only last week only a sac and yolk was seen, no embryo or heartbeat yet. Nothing was seen in my two earlier scans.

basically I want to know the accuracy of early dating scans, and that there is no way it’s the first guys? If it was it would put me at 7/8 weeks on my last scan when not much was seen more than yolk and sac. Thanks :)

Congratulations OP!

I can't speak for the general accuracy, but from experience our dating scan was just 1 day off.

We fell pregnant via IVF so know exact dates for egg collection, transfer etc

We had confirmation of a heartbeat at 6 weeks 5 days pregnant, so if it was the first guys, they'd be expecting to see a heartbeat by now I imagine.

If you had a period after you slept with first guy, it's unlikely he'd be the father.

Sounds like it's not the first guy. You'd expect a sac by 7-8 weeks. Would have also expected positive test by 16th august as technically you'd be 6 weeks then if tracking back to last period (assuming ovulation 2 weeks after that)