Gender at 13 weeks?

Hannah
Ok, so I had a misunderstanding at my OB office with the initial ultrasound. I never really got one. I had two that were crazy fast (less than 4 minutes combined). So they called me yesterday and said they had set up on for next Monday. At that point, I will be 12+6. So almost 13 weeks. If they see the baby's gender, how accurate is it likely to be? I'm just curious. This is my third, I have a girl and a boy and would love another of each. Lol!