I've also heard it. But there has been a study to determine the crediblity of this theory and it has been proven wrong. There is no significance to it. I read the study somewhere on the net. I can't remember the site, but I might do a search for it to see what I can find. I know that with Emily it was alway in the middle range. When I had my u/s with this one the heart rate was 164.

Tanya