Fetal Heart Rate: Knowing what’s normal

What is the normal fetal heart rate? 

Generally, for women 15 to 28 weeks pregnant, it is safe to measure 3 times a day for 1 minute per session. For pregnant women after 28 weeks of gestation, the fetus is fully differentiated, by then the time and frequency of monitoring can be lengthened and increased.

For high-risk pregnant women after 35 weeks of pregnancy (pregnancy-induced hypertension, hyperthyroidism, etc.), they should be hospitalized to continuously monitor the fetal heart.

Fetal heart rate is a means to predict fetal safety, so every pregnant woman must make a record of their fetal heart rate. During this time, pregnant women must know the normal range of fetal heart rate:

1. The normal fetal heart rate is 120 ~ 160 times / min
2. Before 20 weeks of pregnancy, the average fetal heart rate is 162 beats per minute
3. The average of 147 times / min during 21 ~ 30 weeks of pregnancy
4. The average is 139 times per minute during the 31st to 40th week of pregnancy

Causes of abnormal fetal heart rate

The fetal heart rate of the pregnant woman will often exceed 160 beats per minute in the pregnant woman has hyperthyroidism and certain medicines, such as atorpine, can cause the mother and child’s heart rate to accelerate.

Slow fetal heart rate may be caused by fetal hypoxia, congenital heart disease  or certain medications, like propranolol, which acts on the fetus through the placenta, causing the fetal heart rate to slow down. 

In addition, after more than 40 weeks of pregnancy, due to the development of the fetal nervous system, the fetal heart rate may sometimes be less than 120 times. Therefore, when there is an abnormal fetal heart, please seek medical attention immediately for examination.

How to measure fetal heart rate

When listening to fetal heart sounds, the pregnant woman takes the supine position with her head slightly above her abdomen and her legs straight. 

The examiner stands on the right side of the pregnant woman, puts the stethoscope in the middle of the pregnant woman’s umbilicus, moves slightly to the left or right, and slowly moves back and forth.

In addition, expecting mothers can also pay attention and observe the doctor’s position & the placement of the stethoscope and listen to it again after returning home to determine the position of the fetal heart. 

Since fetal movement is usually the movement of the hands and feet of the fetus, when the right side feels frequent fetal movement, the fetal heart is generally on the left side; when the left side feels frequent fetal movement, the fetal heart is generally on the right side. 

The head position and breech position can also affect the position of the fetal heart. In the head position, the fetal heart is below the umbilicus, and in the buttock position, the fetal heart is above the umbilical.