My hospital would not tell you unless they were 90% or more certain of the sex. For boys it is easier apparently but they said for girls they have to see the labia before they can say for certain. If they are unsure, they will not tell you.
When I had my 20 week scan, I was told a girl and could see what they were looking at. However, I played ignorant and asked at the end once again how they could tell it was a girl and the sonographer went back and showed me exactly
Let's hope it's right as I've gone for the pinks and we've named her already. We have NO names for a boy

Mind you, I'm sure a little boy won't mind pink to start with

LOL