Abnormality early pregnancy

I had a scan at 7 weeks my babies heart beat was normal. I’m now 12 weeks and I just received a letter from my GP saying there was an abnormality in the scan and that I need to make a non urgent appointment. It’s non urgent but what could be an abnormality? I can’t go to the doctors until Tuesday because they’re closed until then. I had blood tests at 10 weeks and everything was normal and my HCG levels were high and my doctor just said it just means I’m over 10 weeks.

Please help!!!!! Has anyone had this???????