3D ultrasounds?

Marilyn

when is the best time to do 3-4D ultrasounds? I hear different opinions. "third trimester, because you can see more of the profile" and "mid-late second trimester because they're more active and you can see more movement". I want to hear your opinion on when to go in for a 3D ultrasound. I am 21 weeks today, and thought of doing them in a few weeks.