Heartbeat high for girl,low for boy,do you think its a wives tale??

I'm just wondering If it was true for any of you mommies out there?? We just found out our insurance wont cover an ultrasound that isnt "needed" so we arent going to be able to find out what we are having. I've heard that this is a wives tale,I was just wondering what other people think about it? My daughters heartbeat was always in the 150's range,so it was pretty true for her,she was pretty close to the middle though. Just curiousity I guess...lol.