So I had my first sonogram today and my baby’s heart rate was 142 ...I’ve heard the old wive tales of it being a boy if it’s a low rate and a girl if it’s a high rate

This is baby number 2 for us . We already have a boy and his heart rate was always in the 150s range when we’d get sonograms for him and id say that was pretty low so that was true for us I just don’t know if it’s right every time !? Or have any of y’all had a low rate and it be a girl ??