Heartbeat to determine gender

For anyone who doesn't know your baby's sex yet and enjoys checking out the various silly wives tales I found a website that goes along with the heartbeat test (>140 girl, <140 boy) but it also takes into account gestational age since heartrate goes up then down. Www.babybpm.com :) my baby's heartbeat yesterday at 13w2days was 154 so according to the wives tale it should be girl but according to the website it's boy! Can't wait til my next ultrasound to find out but fun to guess for now!