So naturally, something that I wondered about as soon as we had that first Doppler ultrasound read on the baby’s heartbeat was, how fast should my baby’s heart actually be beating? Here’s some research on what’s “normal!”
This is a great image to depict your baby’s heart growth through gestation.
Baby’s heart starts beating consistently around the 5-week mark. A typical heart rate between 5-6 weeks is about 110 BPM. It then increases to about 170 BPM by 9-10 weeks. This is typically when a Doppler will pick up the fetal heart rate at your doctors appointment. The heart rate then begins to decrease as the baby grows. By 14 weeks, the heart rate is usually around 150 BPM, by 20 weeks around 140 BPM, and by 40 weeks around 130 BPM. These heart rates can vary by 5-15 BPM and remain within normal limits. Also, baby’s heart rate will change depending on how active he or she is, just as yours does.
If you’re curious about heart rate and relation to miscarriages, here are 2 simple charts that give you an average rate of miscarriages based on fetal heart rate at 6 weeks and 2 days as well as between 6 weeks and 3 days to 7 weeks (seen on an ultrasound).
*Note that in this study, after 7 weeks, the fetal heart rate was at or above 120 BPM for all ongoing pregnancies*
Also, here’s a pretty neat graph that shows the fetal heart rates for about 600 pregnant women at 24, 30, 32 and 36 weeks.
Fetal Heart Rate and Variability. Monographs of the Society for Research in Child Development. September 2015; 80.