The heart rate is definitely just a myth. Your baby's heart rate will naturally fluctuate throughout the pregnancy- sometimes it will be faster, sometimes it will be slower. It is not any indication of gender. The only way for you to know now is to give birth. I would like to know where this doctor is located that has a policy not to tell parents the sex so that I never go there for treatment! That is the stupidest thing I've ever heard! Have you thought about getting a private ultrasound done somewhere else? You would have to pay out of pocket for it, but I can't imagine not knowing the sex of my baby. I would want to get stuff for the baby ahead of time, clothes, bottles, other baby accessories, and I want those things to be pink or blue! You don't have time after the baby is born.