heart rate theories?

Parp
I had an ultra sound at 9 weeks 5 days, and the baby was measuring that same size. The heartbeat was 188. I've heard girls have higher heart rates, however so do Down syndrome babies? Does anyone have further knowledge? 
Edit: thank you for your responses! I really appreciate each one. Helps me to chill out and just wait til my blood panorama to find out if it's a girl/boy &/or chromosomal abnormalities. 

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