Ultrasound last Thurs at 13w6d showed a boy?

I had an ultrasound last week and as my hubby and I were discussing whether or not we wanted to find out the gender, the Tech chimed in that she had a pretty good idea of what it was already. I was shocked because I honestly did not think you could see this early. She pointed to the screen and what I saw indicated a boy and she said she was "pretty sure" that's what it was. I've also have been having some instincts that we are having a boy as well. I had a doc appt. after and asked her about it and she said that there is a marker this early that indicates a 85% chance of it being a boy. Do you think this may change based on how early the ultrsound was? I'll be going back at 18 weeks, so I'm sure I'll get more accurate prediction.