What are the Common Causes of a Low Fetal Heart Rate?

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  • Written By: Autumn Rivers
  • Edited By: Andrew Jones
  • Last Modified Date: 16 October 2019
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Low fetal heart rate, also called bradycardia, is the term used when an unborn baby's heart displays fewer than 110 beats per minute. In most cases, it is a temporary situation, though the cause usually needs to be determined in order for the issue to be treated. One of the most common causes is medication taken by the mother, such as narcotics, an epidural, or synthetic oxytocin. Hypotension in the mother can also result in a reduced fetal heart rate, whether for just a few minutes or long-term. Finally, a prolapse or compression of the umbilical cord may also lead to bradycardia in an unborn baby.

This issue often happens during labor due to the number of drugs that many women receive. For instance, synthetic oxytocin is often given to stimulate labor, but in some cases, it can produce hyperstimulation of the uterus. The result is sometimes fetal hypoxia, which is a lack of oxygen that is made obvious by a heart rate that is suddenly lower than average. Women who take narcotics during the pregnancy may also end up slowing down their unborn baby's heart rate, as this type of drug can reduce the chances of the fetal heart accepting adrenaline, which is a hormone that speeds up the heart. Additionally, many women are given an epidural to stop the pain of labor, but this too can sometimes cause temporary hypotension in the mother.


Some women experience hypotension on their own, without having any medications to cause it. One of the most common causes of maternal hypotension is lying flat on the back, as this position can put pressure on the vena cava. The result is less oxygen to the baby, which ultimately leads to low fetal heart rate. For this reason, women are advised to avoid lying flat on their back after about 16 weeks of pregnancy, though it should be noted that most pregnant women feel the effects of this position before any harm is caused to the baby. For example, pregnant women are likely to feel lightheaded after just a few minutes of lying down flat.

In other cases, the umbilical cord can become compressed, or even prolapse. Either way, the fetus does not get enough oxygen when this occurs, thereby causing a low fetal heart rate over time. This is considered an emergency, as it can be fatal to the unborn baby if not fixed quickly. This may occur during a long labor, resulting in a need for an emergency c-section. It is possible, however, for an umbilical cord prolapse to occur at any time, which is why women are advised to see their doctor quickly if they notice a reduction in fetal movement since this often signals low fetal heart rate.


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Post 4

My first fetal heartbeat was recorded at 50 per minute. I'm seven weeks pregnant, but my doctor is still positive she has given me some medicines like Susten 400 twice a day and one more for intestine bacterial clearance. She has advised me to come after 10 days again for an ultrasound. I am really worried about this low heart rate. Can it get better over time?

Post 3

@feruze-- Are you sleeping on your side? My little one had a low fetal heart rate for a part of my pregnancy because I slept on my back. As soon as I started sleeping on my side, everything returned to normal.

Post 2

@feruze-- It may or may not be normal. If it's temporary, then it's probably normal. If it's constant, I'm sure your doctor will do further tests to figure out why.

I have heard that in the first trimester, fetal heart rate can be slower than normal and that it will pick up soon after. It might have to do with the fact that the heart starts beating in the first trimester. My baby's heartbeat was also a little lower than the normal fetal heart rate in the beginning, it was around 100 at six and a half weeks. Then, a few weeks later, it went up to 140 and stayed constant.

Don't worry about it right now. Go for your check up and hopefully your baby's heart rate is in the normal range this time.

Post 1

Is it normal for an unborn baby to have a low fetal heart rate early in the pregnancy?

I just had my first fetal heartbeat check and it was 95 per minute and I'm at six weeks. Should I be worried? My doctor didn't seem worried but asked me to return for a check up in a few days to check the heart rate again.

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