Fetal Heart Rate Monitoring

Fetal heart rate (FHR) monitoring measures the speed and pattern of the fetal heartbeat, which are signs of health. It’s a common test that healthcare providers use during pregnancy and labor.

Times in which your provider may use FHR monitoring include:

• Prenatal visits: Your healthcare provider may check the FHR to make sure it’s in a healthy range.
• Labor and delivery: Monitoring shows how the FHR changes with contractions. Nearly 90% of pregnant women in the U.S. have external fetal monitoring during labor.
• High-risk pregnancies: These are pregnancies complicated by medical conditions like heart disease, preeclampsia, diabetes or intrauterine growth restriction.

FHR monitoring is a safe way to get real-time information about fetal health. You may have lots of questions about what the results mean. Your healthcare provider will be by your side to explain the results and whether they affect the next steps of your pregnancy or labor.

Why is it done?

With monitoring, your provider can tell if the fetal heart rate is too high, too low or changes too much. It’s a standard test because it’s noninvasive. And it’s a simple way to catch issues if they develop.

Irregularities in the heart rate could mean the fetus isn’t getting enough oxygen or has other problems. If your provider sees this, you may need other testing or emergency delivery.

What are the types of fetal heart rate monitoring?

Your healthcare provider can measure fetal heart rate (FHR) with several tools. These tools fall under two main categories: external and internal monitoring.

External monitoring

External monitoring happens on the outside of your belly. Types include:

• Handheld Doppler ultrasound: This tool uses sound waves to measure FHR. Providers often use it during prenatal visits. Your provider squeezes gel onto your belly and places the probe there. The device picks up the heart rate and displays the readout on a screen. If your labor is uncomplicated, a nurse or midwife may use this intermittently.
• Nonstress test (NST): This is a 20- to 30-minute test that measures fetal heart rate in response to movement. It checks for fetal well-being.
• Continuous electronic fetal monitoring (EFM): This tool is mainly for labor and delivery. Most will have some EFM during labor. It’s necessary when your labor is induced or augmented and when you have an epidural. You can often use special wireless monitors so you can still move freely in labor.

Handheld Doppler fetal heart rate monitors are widely sold for at-home use. Ask your provider about the risks and benefits of at-home tools to help you decide what’s best for you and your pregnancy.

Internal monitoring

Less often, your provider may want to directly monitor the fetus during labor. This is called internal monitoring. Your provider attaches a wire to the fetus’s head to continuously track the heart rate. They may also place a pressure catheter inside your uterus to better monitor the strength of your contractions.

Providers use this only after your water has broken. You may need it if external monitoring results are unreliable or you need more precise monitoring.

What are the benefits and risks of this test?

In general, fetal heart rate monitoring is safe. The main benefit is that it can detect fetal distress early. This means your healthcare team can act quickly to correct issues.

Continuous EFM can restrict your movement. This may prolong your labor. It also comes with a risk of false-positive results. This means it may appear to detect a problem that doesn’t exist. These results increase the risk of an unnecessary C-section or assisted vaginal delivery.

Internal monitoring can increase the risk of injury to your baby’s scalp and maternal infection.

Your healthcare team will go over the risks and benefits of each type of monitoring. Ask your care team lots of questions during your prenatal visits. This way, you can create a birth preferences sheet to review with your labor and delivery team when you’re admitted to the hospital.

When should I know the results of the test?

Your healthcare provider will let you know how the fetus is doing right away.

What type of results do you get and what do the results mean?

Depending on how far along you are in your pregnancy, your healthcare provider may measure the baseline fetal heart rate (FHR) and/or changes in heart rate.

Baseline FHR

In general, the possible results of the baseline fetal heart rate include:

• Normal: 110 to 160 beats per minute (bpm)
• Slow (bradycardia): Less than 110 bpm
• Fast (tachycardia): Over 180 bpm

These numbers may vary slightly depending on the stage of your pregnancy. Your provider will let you know what the results mean.

Accelerations

Accelerations are increases in FHR in response to fetal movement. In general, accelerations are a good sign that the fetus is getting enough oxygen. Providers mainly keep track of accelerations during nonstress tests.

Decelerations

During labor, providers pay close attention to decelerations. These are temporary decreases in the FHR due to uterine contractions. There are three types:

• Early deceleration: The fetal heart rate lowers during a contraction and returns to baseline. It lowers due to the squeezing of the fetal head. Early decelerations are common and expected.
• Late deceleration: There’s a drop in the fetal heart rate after a contraction. A decrease in blood flow in the placenta causes it. This could mean the fetus isn’t getting enough oxygen.
• Variable deceleration: The fetal heart rate drops quickly and stays low for longer than typical before returning to baseline. Umbilical cord compression causes variable decelerations.

What if fetal heart rate monitoring shows a problem?

An abnormal heart rate or deceleration doesn’t always mean the fetus is in danger. Your provider may continue monitoring and/or recommend therapies like:

• Changing the position you’re in
• Getting IV fluids
• Adding fluid to your uterus
• Reducing or stopping labor medications (like oxytocin, for example)

Significant changes in fetal heart rate, like bradycardia that lasts 10 minutes or more, are a serious concern. If this happens, your provider may consider an immediate C-section or a vaginal delivery using a vacuum or forceps.