is this heart rate normal?

Catherine
I'm at the Dr right now and I'll be 13 weeks tomorrow. They found the baby's hr on a Doppler and it's 121. Is this normal? I feel like it's low... 
4 weeks ago it was around 145-156
And at week 6 it was 138
Opinions? I'm just worried 

Glow Resources

Let’s Glow

Glow is here for you on your path to pregnancy

Glow helps you navigate your fertility journey with smart tools, personalized insights, and guidance from medical experts who understand what matters most.

25+ million

Users

4.8 stars

200k+ app ratings

20+

Medical advisors