How accurate was an early gender prediction via ultrasound?

Lexy
So we had an ultrasound and I was measuring 13w5d and was told there was a high chance of it being a girl- believe he based it on nub theory... Said it was horizontal? I would have thought it was far too early and am not 100% sold given my I am craving more foods like I did when pregnant with my son, but am still sick/vomiting at 18weeks which I was very unwell with my daughter. My hubby and I also had a dream the same night we were having a boy...  Find out for sure May 6th but would love to hear other people's experiences  thanks! X