My scan took probably around 40 mins or so and as Sherie said, they do all the measurements...head, arm bones, leg bones etc...check the heart, kidneys, stomach...I remember the lady commenting on the stomach to me saying it was a nice little fat tummy and could see the baby had been swallowing which is good cos that's to do with kidney function and the baby peeing to making more amniotic fluid. She asked if we wanted to know gender and I asked if we got pics before she started and she said yes. Try to not be afraid, think of it as they are working for you and you have the right to ask things You will wonder what you were worried about when you come out. If DH is going with you, get him to ask...lol...that's what I do if I'm afraid it's an answer I won't like.