The Common Vein
Intrauterine Pulse Rates
The fetal begins beating at a rate near the maternal rate at rest, being about 75-80 beats per minute (bpm). By 7 weeks (LMP week 9) it accelerates to 165-185 bpm, an increase of 100 bpm in the first month. It then decelerates to about 150 bpm at week 13 (week 15 after the LMP), and by term it is about 145 bpm.
There is no difference in male and female heart rates before birth.
Modified from The Merck Veterinary Manual 6th Edition 1986