They won't write it down as they can't 100% be sure. I think they are more confident if it's a girl than a boy. I'd say a Private scan and blood test is probably your best bet if you want to do this
The only way you’re going to get this is by booking a private scan. They may not even tell you gender at the 20 week scan 😊
Personally I would write a declaration on a piece of paper, stating that "The Sonographer department and NHS personnel involved aren't responsible for the gender being 100% accurate, and can only go on expertise in that moment and what their see" Sign and date it with your name and signature, Then leave a space underneath, write "predicted gender" so they can put there for you in that space... See if they will write that down then? It takes responsibility away or whatever and they might bypass their rules for you.. Probably a silly idea but the only thing I can think of that they will accept in that moment? xx
They definitely don't write it down. Gender determination isn't the objective of the 20 week scan so they will just tell you verbally if indicators are there and you want to know. You would need to have a private scan if you want to do a reveal.