A normal fetal heartbeat is one of the most reassuring sounds expectant parents will ever hear, as it normally indicates that all is well with a developing pregnancy. At different stages of a pregnancy, the fetal heartbeat can be seen on an ultrasound, heard using a doppler or heard using a regular stethoscope. Doctors often use the fetal heartbeat to determine if there is a problem with the growing fetus that needs further attention.
The fetal heartbeat starts beating during the embryonic stage of pregnancy at 22 days after conception, or what is considered the fifth week of pregnancy. However, it is much too small to be heard using a doppler at this stage, so doctors frequently use ultrasounds to confirm a pregnancy and measure the early fetal heartbeat. Beginning at 10 to 12 weeks of pregnancy, doctors are able to use fetal doppler instruments to hear the heartbeat, and they often continue to use the doppler to check the fetal heartbeat at all subsequent prenatal visits. Expecting parents often take comfort in "checking in" with their growing baby and hearing a normal fetal heartbeat at each appointment. A stethoscope placed on the mother's abdomen can also be used to hear the fetal heartbeat beginning at around 20 weeks of pregnancy.
Many expectant parents often have trouble distinguishing between the mother's heartbeat and the fetal heartbeat, while doctors and nurses seem to have no problem telling the two apart. The difference in the two heartbeats is apparent because the fetal heartbeat is much faster than a normal adult heartbeat. While the mother's heartbeat averages around 80 beats per minute (bpm), the fetal heartbeat averages between 120 and 160 bpm.
While the average normal fetal heartbeat ranges between 120 and 160 bpm, this number can vary somewhat in the early stages of pregnancy. Starting at day 22 post-conception, it is normal for the fetal heartbeat to be somewhat lower than 120 bpm, usually between 80 and 100 bpm. This rate continues to increase each week, topping out at 155 to 195 bpm at 9 weeks of pregnancy before settling down to the normal 120 to 160 bpm range at 12 weeks.
What makes seeing a normal fetal heartbeat on an ultrasound or hearing it on a doppler so comforting to parents is that the presence of a normal fetal heartbeat greatly reduces the chance of miscarriage. Miscarriage occurs in only 1 percent of pregnancies where a normal fetal heartbeat has been seen or heard, while it is estimated that miscarriages occur in 15 to 20 percent of all pregnancies. While not always the case, fetal heartbeats below the accepted normal range may indicate fetal demise and impending miscarriage.
There is a highly touted old wives' tale surrounding the fetal heartbeat and gender identification that many people believe to be true, but which is only a superstition grounded in no scientific evidence. The old wives' tale suggests that a fetal heartbeat of 140 bpm indicates that the baby is a girl, while fetal heartbeats below 140 bpm identify the baby as a boy. This hypothesis is based on the idea that females have higher metabolisms than males, but there is no evidence to support this.