Women's Health

Electronic Fetal Monitoring

Test Overview

Electronic fetal monitoring is done during pregnancy, labor, and delivery. It keeps track of the heart rate of your baby (fetus). It also checks the duration of the contractions of your uterus. Your baby's heart rate is a good way to tell if your baby is doing well or may have some problems.

Two types of monitoring can be done: external and internal.

External monitoring

External monitoring is done during labor. And you may have it done at other times during your pregnancy also.

External monitoring is done using two flat devices (sensors). They are held in place with elastic belts on your belly. One sensor uses reflected sound waves (ultrasound) to keep track of your baby's heart rate. The other sensor measures how long your contractions last. The sensors are connected to a machine that records the details. Your baby's heartbeat may be heard as a beeping sound or printed out on a chart. How often you have contractions and how long they last may be printed on a chart.

External monitoring is used for a nonstress test. This test records your baby's heart rate while your baby is moving and not moving. A nonstress test may be done with a fetal ultrasound to check the amount of amniotic fluid.

External monitoring is also done for a contraction stress test. This test records changes in your baby's heart rate when you have contractions. It may be done to check on your baby's health if your baby does not move enough during a nonstress test. It may help predict whether your baby can handle the stress of labor and vaginal delivery.

Sometimes external monitoring is done remotely. This is called telemetry. It allows you to be checked without being hooked up to a machine. At some hospitals, the sensors can send the details about your baby's heart rate and your contractions to a remote monitor. This monitor is usually at a nurse's station. Using a remote monitor allows you to walk around freely.

Internal monitoring

Internal monitoring is done during labor. It can be done only after your cervix has dilated to at least 2 centimeters (cm). Your amniotic sac must have ruptured as well. After it is started, it is continued until delivery.

For internal monitoring, a sensor is strapped to your thigh. A thin wire (electrode) from the sensor is put through your cervix and attached to your baby's scalp. Your baby's heartbeat may be heard as a beeping sound or printed out on a chart.

A small tube that measures contractions may be placed through your cervix and into your uterus. The strength and timing of your contractions is often printed out on a chart.

Internal monitoring may be used if it is difficult to clearly record your contractions or the baby's heart rate with the external monitor.

Why It Is Done

External monitoring

This type of monitoring is done to:

  • Keep track of your baby's heart rate.
  • Measure how often you have contractions and how long they last.
  • Find out if you are having preterm labor.
  • Check on your baby's health if your doctor thinks there may be problems. External electronic fetal monitoring will be done during a nonstress test to check your baby's heart rate while at rest and while moving. If your baby does not move during this test, more tests will be needed.
  • Check your baby's health if your doctor thinks the baby is not getting enough oxygen because of problems with the placenta. If a stress test shows that your baby is not getting enough oxygen, your doctor may suggest starting (inducing) labor early. Or your doctor may talk to you about a cesarean section (C-section).
  • Check your baby's health if your baby has not been growing normally. (This is called delayed fetal growth.) Monitoring may also be done if you have diabetes or high blood pressure or if you are over 41 weeks pregnant.

Internal monitoring

This type of monitoring is done to:

  • Find out if the stress of labor is putting your baby's health at risk.
  • Measure the strength and length of your labor contractions.

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

External monitoring can be done at any time after 20 weeks of pregnancy. Internal monitoring is used only when you are in labor and your amniotic sac has broken. If it is needed and your amniotic sac has not broken, your doctor may break the sac to start the test.

Sometimes both types of monitoring will be done at the same time. Your baby's heart rate may be checked with an internal sensor, and your contractions may be checked with an external or internal sensor.

External monitoring

For external monitoring, you may lie on your back or left side. Two belts with sensors attached will be placed around your belly. Gel may be applied to provide good contact between the heart rate sensors and your skin. The sensors are attached with wires to a recording device. This device can show or print out a record of your baby's heart rate and the duration of contractions. The position of the heart rate monitor may be changed now and then as your baby moves.

For a nonstress test, you may be asked to push a button on the machine every time your baby moves or you have a contraction. Your baby's heart rate is recorded. Then it's compared to the record of movement or your contractions. This test usually lasts about 20 to 40 minutes.

Internal monitoring

For internal monitoring, you will usually lie on your back or left side. A thin wire (electrode) will be put through your cervix and attached to your baby's scalp. A band is placed around your upper leg to keep the monitor in place. The electrode is attached with wires to a recording device that can show or print out a record of your baby's heart rate.

In some cases a small tube that measures contractions may also be placed through your cervix and into your uterus. The tube connects to the recording device, which shows or prints the strength and length of your contractions.

How It Feels

You may have some discomfort if you are having contractions. And the belts that hold the sensors in place may feel tight.

You may be able to change position or move around more during internal monitoring than during external monitoring.

You may have discomfort if an internal contraction monitor is put into your uterus.

Risks

Electronic fetal monitoring may be linked to an increase in cesarean deliveries. It may also be linked to the use of a vacuum or forceps during delivery.footnote 1

There is a slight risk of infection for your baby when internal monitoring is done.

Results

The results are usually ready right away. Here are some examples of normal and abnormal results.

Electronic fetal monitoring

Normal:

Your baby's heart rate is 110 to 160 beats per minute.

Your baby's heart rate increases when the baby moves and when your uterus contracts.

Your baby's heart rate drops during a contraction but quickly goes back to normal after the contraction is over.

Uterine contractions during labor are strong and regular.

Abnormal:

Your baby's heart rate is less than 110 beats per minute.

Your baby's heart rate is more than 160 beats per minute.

During a nonstress test, your baby's heart rate does not increase by 15 beats per minute or it drops far below its baseline rate after the baby moves.

Your baby's heart rate gets slower and stays slow after a contraction.

Uterine contractions are weak or irregular during labor.

Fetal monitoring can't find every type of problem, such as birth defects. A normal result does not guarantee that your baby is healthy.

References

Citations

  1. Alfirevic Z, et al. (2017). Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour. Cochrane Database of Systematic Reviews, 2(2): CD006066. DOI: 10.1002/14651858.CD006066.pub3.

Credits

Current as of: July 11, 2023

Author: Healthwise Staff
Clinical Review Board: All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.