With my first baby mu one and only scan was at 18weeks.
With no two I had a dating scan due to me not knowing my dates we were not ttc and I was on contreception so I really didn't know.
With my last I had scans at 4.5, 5.5, 6weeks to see if she was in the right spot as I had an ectopic pregnancy and my only tube was damaged so high chance of a repeat. I had another scan at 10weeks, 11weeks and 12weeks for peace of mind (they took all of 30secs literally to see her and her heart beating and that was it)