So what is the myth exactly, girls HR are higher and boys lower....but what are the approx numbers? This bub seems to be in between...maybe its a hermaphrodyte....LOL. It's heart rates have been 146bpm @ 7wks, 157 @ 18wks and 159 @ 29wks. Though 18wk U/S said boy, I still have it in my head that there's a chance it's a girl! Maybe just wishful thinking!