Just lie down while the doctor do the scan. They'll measure everything and they can even check if the kid has cleft lips. If there is a hole in the heart. Quite cool. And they might be able to see what the baby is doing. But personally I lack imagination, so I couldn't figure out how they see that my baby girl is opening her mouth. -.- but yeah. Stuff like that. The entire procedure if baby cooperates would be quick but if you got an active kid (depends some move super early so as mommy you all will know. Average movement is once per hour) then the image might be difficult to focus I think. Lol. But it'll be fun. It'll give you a peace of mind thereafter.