Both my babies have hated having the u/s done, this time around I actually have declined a few chances at having ones done because I didn't think they were necessary. I have had 3 done and probably would have been happy with just 1 at the 18-20 weeks. I read some information similar to what Alan has posted & decided it wasn't something I would do more of if I had a choice, obviously if there were complications I would go for it.