First ultrasound. Heart rate question

Mrs.C
Was so nervous cause I had light spotting a couple days ago and barely have any symptoms besides sore breasts. Had my 6 week ultrasound today. I found out that I'm actually 6 weeks 3 days along. Baby's heart rate is at 152. As per the tech if the heart rate is above 140 there's a high chance that it's a girl. Has anyone else heard this before?