It was correct with my first pregnancy. The heart rate was around 130 and we had a boy. My sister never found out the sex till she gave birth. I thought for sure she was having a girl cuz the babys heart rate was 168. She had a boy. Im now 15weeks with my second at the heart rate is 160 so Im so hoping for a girl.
It's a myth. I'm 14 weeks 2 days and was able to see that I am having a boy on a 3D ultrasound. My baby's heart beat is 155 and according to that im going to have a girl. It would be nice to know for sure without having to wait, but you may have to until you get your 20 week scan. But why not try it you have a 50/50 chance of being right.