I was 7 weeks for my first u/s and they did on the belly and then vaginally to see better... should just be belly I would assume.
At 12 weeks you should pretty much have a small baby. And it sometimes depends on where the baby is sitting my first u/s was vaginally cause this baby is in my back and i was also only 6 weeks. With my son it was 8 weeks and they did it on my stomach...
I searched YouTube before my 12 wk scan there's lots of images and videos etc so it gave me a good understanding of what I should see and what to look for etc. I found it helpful it helped calm my nerves
I had my first ultrasound at 12 weeks and they did it on my stomach. I was surprised how it looked when she was in the fetal position she just kinda looked like a ball lol but then she stretched and looked amazing!! You could almost count all five toes lol she looked just like a real baby.....if that makes sense lol. Wish I could post a pick