Test Overview

Electronic fetal heart 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

You may have
external monitoring at different times during your pregnancy. Sometimes it’s done
during labor.

External monitoring can be done by listening to your
baby’s heartbeat with a special stethoscope. More often, it 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 into your uterus. The electrode is
then 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 in your uterus next to your
baby. The strength and timing of your contractions is often printed
out on a chart.

Internal monitoring is more exact than external
monitoring for keeping track of your baby’s heart rate and your
contractions.

Why It Is Done

External fetal heart 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 fetal heart 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
    placenta to make sure that it is giving your baby
    enough oxygen. If a stress test shows that your baby is not
    getting enough oxygen, your doctor can decide about the safest
    way to deliver. If the test shows that your baby may be in danger, 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 fetal heart 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

You may be asked to eat a meal shortly
before you have a nonstress test. When you digest food, it often causes a baby to move more.

If you smoke, you will be asked to stop smoking for 2
hours before external monitoring. Smoking causes a baby to be less active.

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 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 30 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 small tube is also put in your uterus. The tube connects to a device
that monitors your contractions.

A belt is placed around your
upper leg to keep the monitor in place. The electrode and the tube are attached
with wires to a recording device. It can show or print out a record of
your baby’s heart rate and the strength and length of your contractions.

How It Feels

Lying on your back (or side) may not be comfortable if you are having contractions. The belts that hold the monitors 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 some discomfort when the internal 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

Electronic fetal heart 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. The results are usually ready right away.

Electronic fetal monitoring
Normal:

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

Your baby’s heart rate increases when he
or she 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 he or she moves.

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.

What Affects the Test

You may not be able to have the test, or the results may not be helpful, if:

  • You smoke cigarettes or use other tobacco
    products.
  • You drink or eat large amounts of caffeine. (For example, you drink several
    cups of strong coffee.)
  • There are extra noises such as your heartbeat or your stomach
    rumbling.
  • Your baby is sleeping during a nonstress
    test.
  • There are problems with how an external monitoring
    device is placed. This can happen if:

    • Your baby moves a lot during the
      test.
    • You are pregnant with more than one baby.
    • You are overweight.

What To Think About

  • Not everyone feels the same about fetal
    monitoring.

    • Some mothers think that it is not needed and it gets in the way of the natural birthing process.
    • Other mothers think that it is calming.
      This may be true if they had problems with earlier pregnancies.
  • Monitoring throughout
    labor (continuous) is more likely to be useful for high-risk pregnancies. For low-risk pregnancies, monitoring from time to time during labor (intermittent) works just as well.
  • If your baby seems to be having problems,
    a blood sample may be taken from a small blood vessel (capillary) in the scalp. The blood sample can help the doctor see if your baby is getting
    enough oxygen.
  • Your baby may move more if you drink juice
    or eat before a nonstress test. This may make the test results more
    useful.
  • Sometimes other methods (such as ringing a bell near the
    uterus) are used to cause changes in your baby’s heart
    rate.
  • External fetal heart monitoring is used during other tests of
    a baby’s health. Examples include a nonstress test, a contraction stress test, and
    a biophysical profile.

Other Places To Get Help

Organization

American Congress of Obstetricians and Gynecologists
(ACOG)
www.acog.org

References

Citations

  1. American College of Obstetricians and Gynecologists (2009, reaffirmed 2015). Intrapartum fetal heart rate monitoring: Nomenclature, interpretation, and general management principles. ACOG Practice Bulletin No. 106. Obstetrics and Gynecology, 114(1): 192-202.

Other Works Consulted

  • American College of Obstetricians and Gynecologists (2010). Management of intrapartum fetal heart rate tracings. ACOG Practice Bulletin No. 116. Obstetrics and Gynecology, 116(5): 1232-1240.
  • Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.

Credits

ByHealthwise Staff
Primary Medical Reviewer Sarah Marshall, MD – Family Medicine
E. Gregory Thompson, MD – Internal Medicine
Kathleen Romito, MD – Family Medicine
Adam Husney, MD – Family Medicine
Specialist Medical Reviewer William Gilbert, MD – Maternal and Fetal Medicine
Femi Olatunbosun, MB, FRCSC – Obstetrics and Gynecology

Current as ofMarch 16, 2017