Gender Ultrasound Monday!

I had my monthly doctors appointment this morning. Got to hear the heartbeat which was at a solid 156. We scheduled our gender Ultrasound on Monday so we can find out what we're having. I'm 18 weeks & the doctor said the baby is big enough. I did some research and I read that with a heartbeat of 156, it could be a girl based on the fact that girls have higher metabolism. The research isn't solid but my husband and I are hoping for a girl!