Old wives tale about a baby's heartbeat determining the sex

Jasmine • I'm a neonatal nurse. I have two little girls and an amazing hubby. My life couldn't be better!!!!
As the old wives' tale has it, if your unborn baby's heart rate is higher, above 140 beats per minute, that means you're carrying a girl. A lower heart rate below 140 bpm means you're having a boy.... Have any of you ladies proven this to be true?? Also, if you have any old wives tales you'd like to talk about, please post them!!!