LOADS of water. I felt like I was going to wet myself and they still said my bladder wasn’t full enough! I had mine at 15 +1 and it did take them a while to get an accurate idea of gender but they usually offer a rescan if they can’t determine it.
I’ve got mine tomorrow and I’ll be 17+5 days and I’ve been told to drink so much water
In the week leading up to it drink loads of water too
They had me doing a truffle shuffle to move that baby around 😂