Fetal heart rate is a term that refers to a baby’s heartbeat while they’re in the uterus. It can provide lots of information about your baby’s health during pregnancy. Healthcare providers usually start listening for a baby’s heart rate at the 10- or 12-week prenatal visit.
From there, providers generally check it during each subsequent prenatal appointment and also monitor it during labor.
This article reviews normal fetal heart rate, how it is measured, who should monitor it, and what causes variations.
Normal Fetal Heart Rate
Healthcare providers measure fetal heart rate by the number of fetal (baby) heartbeats per minute (BPM) during pregnancy. This measurement helps healthcare providers determine the well-being of the fetus during prenatal visits or labor.
Monitoring fetal heart rate during pregnancy has been a focus for doctors and midwives since the 1800s. In 1822, a French obstetrician gave the first written detailed description of fetal heart sounds. Nearly 100 years later, they found that very low heart rate (bradycardia) indicated fetal distress.
The average fetal heart rate varies depending on the stage of pregnancy. Here’s generally what to expect:
- Beginning of pregnancy: A baby’s heart starts to develop around the fifth week of pregnancy. In this early stage, the heart rate starts slow and averages 110 BPM around the sixth week.
- Ninth week of pregnancy: Around the ninth week of pregnancy, the heart rate speeds up to an average of 140 to 170 BPM. By week 12, the rate slows down a bit. Throughout the rest of the pregnancy, the average is 110 to 160 BPM. However, it can vary from 5 to 25 beats per minute.
- Last 10 weeks of pregnancy: During the last trimester, the fetal heart rate continues to average 110 to 160 BPM. However, it drops slightly in the last 10 weeks. In general, it moves towards the lower end of this range the closer you get to your due date.
- Variations: Fetal heart rate varies throughout the day and night due to the baby’s activity level. It increases while they are moving around and decreases while they’re asleep. These changes are similar to what adults experience while exercising or at rest.
Hearing Is Believing
Weeks 10 to 12 of pregnancy are very exciting for expectant parents. It’s typically the first time they hear their baby’s heartbeat during a prenatal visit.
Abnormal Fetal Heart Rate
Sometimes a fetal heart rate is outside the normal range simply because the fetus is moving around. Other times, it indicates a health concern for the baby. When the healthcare team detects a possible problem, their first step will be to try to find the cause.
Depending on the stage of pregnancy, different tests will be used to clarify the problem. Sometimes, a fetal heart rate is abnormal because of something happening in the mother’s body. These are called maternal causes and may include:
- Blood sugar levels
- Low red blood cells (anemia)
- Maternal intake of medications, caffeine, or nicotine
- Thyroid problems
How to Monitor Fetal Heart Rate
The following methods are used to listen to a fetal heart rate:
- Stethoscope: A stethoscope can detect a fetal heartbeat around week 20 or 22 of pregnancy. To use a stethoscope yourself, lie down in a quiet area and place the chest piece on your belly while you listen through the earpiece. If you can feel where the baby is, place the chest piece in the area where you feel their back.
- Fetoscope: A fetoscope is a specific stethoscope used to listen to fetal heart rate.
- Pinard horn: A Pinard horn was previously called a fetoscope. It is a wood or metal trumpet-shaped device that transmits fetal heart sounds to the listener’s ear.
- Fetal Doppler: A fetal Doppler is a hand-held machine that uses non-invasive ultrasound (sound waves) to detect the baby’s blood circulation. This method involves the healthcare provider putting gel on the wand, placing it on your abdomen (belly), and moving it around to find the heartbeat. This is the most common way parents hear their baby’s heartbeat for the first time.
- Transvaginal ultrasound: Prior to weeks 10 to 12, it is difficult to detect a baby’s heartbeat with a Doppler. While it is not common to check for a fetal heart rate earlier in pregnancy, it can typically be detected through a transvaginal ultrasound by week six.
External monitoring means checking the fetal heart rate through the mother’s abdomen (belly). The Doppler machine is an example of external monitoring and can be used during prenatal visits or labor.
Healthcare providers may also use continuous external electronic monitoring during labor. They secure external sensors to the abdomen with an elastic belt or an electrode that resembles a round sticker. The fetal heart rate and contraction information appear on an attached computer screen. Healthcare providers monitor fetal heart rate during labor to watch how the baby responds to contractions, medications, tests, and pushing.
Internally monitoring involves a thin wire and electrode placed through the cervix and attached to the baby’s scalp. This technique is considered only after a mother’s water has broken and the cervix is dilated or open. It provides more precise readings that are not affected by the baby’s movement.
Who Should Monitor Fetal Heart Rate
A stethoscope or fetoscope can be used by anyone after 20 or 22 weeks of pregnancy. However, it can take some practice to hear the heartbeat using this method, especially if the baby is moving around. Additionally, you may have difficulty detecting the heart rate even when the baby is perfectly fine.
While handheld fetal Dopplers are available over the counter, it is best to consult your healthcare provider before using one. They really aren’t intended for home monitoring.
Occasional use of Dopplers by a healthcare provider is considered safe. However, extensive use at home could lead to unanticipated negative consequences. For example, if it is difficult to find the heartbeat using a Doppler before 16 weeks. This may cause unnecessary worry for parents. Conversely, hearing a fetal heart rate by home Doppler in certain situations may provide a false sense of security when medical attention is actually needed.
Monitoring Risk Factors
Monitoring the fetal heart rate more often can be helpful in high-risk pregnancies. Risk increases with factors such as:
- Maternal age (teens or women over age 35)
- Existing health conditions
- Hypertension (high blood pressure) or preeclampsia
- Maternal diabetes
- Maternal substance use
- Multiple babies (twins, triplets)
- A baby who is not growing properly
- A baby with health concerns or chromosomal abnormalities
A fetal heart rate gives you and your healthcare team information about your baby’s health during pregnancy. Healthcare providers usually start listening for a baby’s heart rate at the 10- to 12-week prenatal visit using a Doppler machine. They continue to monitor it during prenatal appointments and during labor.
Normal variations in fetal heart rate occur when the baby is moving or asleep. While it is not always a cause for concern, fetal heart rates outside the normal range may also indicate fetal distress. It provides your healthcare team with information so they can intervene, if necessary.
A Word From Verywell
Don’t be overly alarmed if you don’t hear your baby’s heartbeat by 10 or 11 weeks. The baby may need to grow for another week or two before you and your healthcare provider can hear it. Sometimes, you may not be as far along as you thought and it’s just too early to hear the heartbeat. Talk with your healthcare provider if you’re concerned about your baby’s heart rate or if your pregnancy is high-risk,
Frequently Asked Questions
What qualifies as a rapid fetal heart rate?
A fetal heart rate greater than 160 beats per minute (BPM) is considered fast. It
is called fetal tachycardia when it is greater than 180 BPM.
Will my heart rate directly affect my baby’s heart rate during pregnancy?
This depends on the source and duration of your increased heart rate. Mild to moderate heart rate changes in otherwise healthy women generally do not negatively affect the baby’s heart rate. However, prolonged anxiety, stress, and high blood pressure could negatively affect your baby’s health.
How can you tell if a fetus is in distress?
The fetal heart rate acts as a screening tool for the healthcare team. A prenatal non-stress test (NST) can be used to assess fetal heart rate and movement at around 26 to 28 weeks of gestation. If the heart rate is out of the normal range, the team can do an ultrasound or order blood work. During labor, they may give the mother oxygen or change her position to see if that helps the baby or if they need to intervene.