Measuring 12w3d

Hello ladies,

So today I’m 12 weeks, 1 day according to my LMP and my due date is sept. 3rd. But when I looked at the ultrasound picture it shows 12 weeks, 3 days. Do you ladies know if the ultrasound pic goes based off their measurement when they do it there or if it from LMP? Also, they said the heart rate was 145bpm and I know It’s too soon to tell but I still asked if they could take a peek at the gender. She said it looks like a girl but it may be too soon. This is my 3rd child and I really want to find out lol!! Have any of you ever predicted the gender based off the heart rate? I know it’s a silly old wives tale but please share. 🙂