Hearing your baby’s heartbeats can be an exciting experience for you. Take a look at the chart presented in this article to know how the heart rate of the fetus changes during pregnancy…
The normal resting heart rate (RHR) of a woman can be anywhere between 60-100 bpm. During pregnancy, a woman may experience an increase of 10-20 beats in her RHR, depending upon various factors like age, weight, overall health, etc. The heartbeat of a baby in the womb is known as fetal heart rate or fetal heart tone (FHT). The unit of measurement is beats per minute. It is measured with the help of a fetal ultrasound doppler. It keeps on changing during the stages of pregnancy.
FHT Chart by Week
|Age or Size of the Fetus||Normal Fetal Heart Rate|
|2 mm embryo and gestational sac diameter of 20 mm||75 bpm|
|5 mm embryo and gestational sac diameter of 30 mm||100 bpm|
|10 mm embryo||120 bpm|
|15 mm embryo||130 bpm|
|5th Week (Beginning)||80-85 bpm|
|5th Week (End)||103 bpm|
|6th Week (Beginning)||103 bpm|
|6th Week (End)||126 bpm|
|7th Week (Beginning)||126 bpm|
|7th Week (End)||149 bpm|
|8th Week (Beginning)||149 bpm|
|8th Week (End)||172 bpm|
|9th Week (Beginning)||155 bpm|
|9th Week (End)||195 bpm (average 175 bpm)|
|12th Week||120-180 bpm (average150 bpm)|
The average FHT varies from fetus to fetus, depending upon several conditions. It keeps on increasing and decreasing during the pregnancy. It can be as high as 180 bpm or as low as 100 bpm. Even 90-110 bpm can be considered as normal heart rate for a 6 weeks old fetus, depending upon the situation. At 9 weeks, 140-170 bpm can be considered as normal heartbeat.
Hearing Fetal Heart Beats
As you know, 40-42 weeks period of pregnancy is divided into three trimesters. Though the heart of the fetus starts beating at around 5th week, the beats are usually audible from 18th week onwards. Don’t panic if you are not able to hear the heartbeats in the 18th week. It will depend upon your own weight, position of the baby, location of the placenta, etc. You may be able to hear the beats in the next week or in the 20th week. It’s quite normal. You can hear the beats with the help of a stethoscope or fetoscope.
Heart Rate and the Age of the Fetus
You must have noticed that in the 5th week, the FHT and the mother’s heart rate (80-85 bpm) are almost the same. But then the FHT increases with an amazing speed, at about 3.3 beats per day for one whole month! After 9th week, it lowers down, and comes to about 150 bpm (average) in the 12th week. The normal FHT range after 12th week is 120-160 bpm. This fixed pattern of change in the FHT helps estimate the age of the fetus.
During the second and third trimester, no major changes in the FHT are noticed. The FHT lowers slightly during the last ten weeks, in the last trimester. But it is still quite higher than the heart rate of an adult (about twice). A range of 100-160 bpm is considered as normal range of FHT.
Absence of heartbeats for a week or more is a sign of impending miscarriage. Placental or umbilical cord problems, psychological or emotional stress on the pregnant woman, excessive physical exertion by the pregnant woman, or any other health complications can lead to abnormally low or high FHT. Very low heart rate at 5-8 weeks (less than 90 bpm) is referred to as fetal bradycardia, and it indicates high risk of miscarriage.
The modern ultrasound technology has made it possible to hear the fetal heartbeats as early as in the 8th week. The heart rate of the fetus may change during physical activities performed by the mother, and during sleep. The rate can be quite different at different periods of time during the same day. Measurement of fetal heart rate helps assess the health of the fetus.
Disclaimer: This HerHaleness article is for informative purposes only, and should not be used as a replacement for expert medical advice.