Gender? Heart rate

I've always heard gender can be determined by the heart rate higher it is more likely to be a girl and under 140 is more likely to be a boy. I'm just wondering has it been right for the majority. My first was 174 and a girl, my 2nd is 178 at 8 and 10 weeks but my husband is praying it's a boy but I joke with him saying it's a girl but I really don't know. So has anyone had a higher rate and it be a boy?