They tried mine at the 20 week ultrasound but she wasn't cooperating. They tried again around 28weeks but again she was facing downward and away from us:/
I had a private one at 16 weeks so I could find out the gender sooner.
Got mine @ 28 weeks. And having another monday and im 33 weeks. the later In pregnancy, the better the ultrasound
I haven't had mine yet but 2 of my friends got theirs at 25 or 26 weeks!