Hello and thanks for the query.
The normal fetal heart rate usually varies somewhere between 110 and 160 beats per minute  throughout pregnancy, but in the early part of the first trimester, the baby's heart rate can be slower. A comparative data is being give below

2 mm embryo: 70 to 75 beats per minute
5 mm embryo: 95 to 100 beats minute
10 mm embryo: 115 to 120 beats per minute
15 mm embryo: 125 to 130 beats per minute
Although viable pregnancies can occasionally have initial heart rates lower than these norms, a slow heart rate in early pregnancy is associated with a higher risk of miscarriage. Doctors usually recommend followup ultrasounds for women whose babies have slow heart rates in order to determine whether or not the pregnancy is viable.
For any issue regarding the fetal heart rate,one must discuss this with the treating doctor.
I hope to have answered your query however you may revert to me for any further query.
Best of luck
Thanks

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