Has the gender been wrong early on

Hey guys,

went for my 12 week scan today and all measuring healthy, actually really long! Anyway we were having a chat about how partner wants a boy and I wouldn’t mind a girl and the ultrasound tech offered to check for us and give us a very early guess. She said boy- obviously it’s very early and we aren’t going to go buy any gender related stuff until our 20 week scan. But just wondering how accurate the early guesses are- we aren’t fussed either way just grateful for a healthy bub 😍