A (hopefully) expectant father here!

[Rhiandell]

That's great news Harvey! And as MrsB said, this early the measurements can be way off, the reason the dating scan is done between 12 and 14 weeks is because that's the most accurate time to date the baby with a scan, outside that window it's typically not very reliable. That being said, it's usually a few days from conception to implantation, and conception can happen up to a few days after doing the deed, as both sperm and eggs can survive "floating around" for quite a while.
And I agree that if you are worried, do call the EPU. That's what they're there for.

Sent from my SM-G850F using Tapatalk