fetal heartbeat question.

Hi I'm 15 weeks and my baby's heartbeat is measuring at 169bpm.

I've read that at this point the heartbeat should be 120-160bmp. Any mom's out there with a high fetal heartbeat at 15 weeks? I'm trying hard not to freak out bc my next ultrasound isn't for another month and it has already been well over a month since the last one.