I was 16 and confirmed with my doctor at 19 that they was little boy parts
Most elective places will have you reschedule if they can't tell you when you go. They don't just keep the money and you leave with nothing.
I want one but the babys father has told me no so many times because if they are wrong he will flip lol he wants to keep the image in his head that its a girl until told otherwise.
I was 14 weeks when I went and it was a perfect shot of girl parts! Our second little girl!!
Are you paying out of pocket for it? They can not "guarantee" anything lol. The genitals are barely even developed at 14 weeks and tons of OBs get it wrong at that time. Also, baby could be in a position that doesn't allow them to even get a look. Legs crossed, turned away, etc. I'd just wait for the anatomy scan if I were you, especially if you have to pay for this one.
Can you have it at any hospital?
I got one at 17 weeks. The day I went, another girl was only 14 weeks. They told her if was a girl. It was accurate for me.