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Electronic fetal heart monitoring is done during pregnancy, labor, and
delivery to keep track of the heart rate of your baby (fetus) and the
strength and duration of the contractions of your
uterus. Your baby's heart rate is a good way to tell
whether your baby is doing well or may have some problems.
types of monitoring—external and internal—can be done.
You may have
external monitoring at different times during your pregnancy, or it may be done
External monitoring can be done by listening to your
baby's heartbeat with a special stethoscope. More often, external monitoring is
done using two flat devices (sensors) 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 the duration of your contractions.
The sensors are connected to a machine that records the information. Your
baby's heartbeat may be heard as a beeping sound or printed out on a chart. The
frequency and duration of your uterine contractions are usually printed out on
External monitoring is used for a
nonstress test, which records your baby's heart rate
while your baby is moving and not moving. A nonstress test may be combined with
fetal ultrasound to evaluate the amount of your
External monitoring is also done for a
contraction stress test, which records changes in your
baby's heart rate when you have uterine 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
Sometimes external monitoring is done remotely
(called telemetry), without your needing to be connected by wires to a machine.
At some hospitals, the sensors can send the information about your baby's heart
rate and your uterine contractions to a remote monitor, usually at a nurse's
station. Remote monitoring allows you to walk around freely.
Internal monitoring can be
done only after your
cervix has dilated to at least 2 centimeters (cm) and
amniotic sac has ruptured. Once started, internal
monitoring is done continuously.
For internal monitoring, a sensor
is attached to your thigh with a strap. A thin wire (electrode) from the sensor
is inserted through your vagina and 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. Internal monitoring does not use
reflected sound waves (ultrasound) for monitoring.
A small tube
that measures uterine contractions may be placed in your uterus next to your
baby. The strength and timing of your uterine contractions is usually printed
out on a chart.
Internal monitoring is more accurate than external
monitoring for keeping track of your baby's heart rate and your
External fetal heart monitoring is done to:
Internal fetal heart monitoring is
You may be asked to eat a meal shortly
before having a nonstress test, because digesting food often increases the
movement of your baby.
If you smoke, you will be asked to stop smoking for 2
hours before the external monitoring test because smoking decreases your baby's
External monitoring can be done any
time after 20 weeks of pregnancy. Internal monitoring is used only when you are
in labor and your amniotic sac has broken. If internal monitoring is needed and
your amniotic sac has not broken, your doctor may break the sac to begin the
test. Sometimes a combination of internal and external monitoring is done by
measuring your baby's heart rate with an internal sensor and measuring your
contractions with an external sensor.
For external monitoring, you
will usually lie on a examination table or bed on your back or left side. Two belts with sensors
attached will be placed around your belly. One belt holds the sensor that keeps
track of your baby's heart rate, while the other measures the timing and
strength of your uterine contractions. 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 that can indicate or print out a record of
your baby's heart rate as well as the strength and duration of uterine
contractions. The position of the heart rate monitor may be changed
periodically to adjust to the movement of your baby.
nonstress test, the sensors are placed on your belly. 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 and compared to the record of movement or
your contractions. This test usually lasts about 30 minutes.
For internal monitoring, you
will usually lie on a bed on your back or left side. A thin wire (electrode)
will be guided through your vagina and cervix and attached to your baby's
scalp. A small tube is also inserted through your vagina to connect a device
that monitors the contractions inside your uterus. 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 that can show or print out a record of
your baby's heart rate as well as the strength and duration of your uterine
Lying on your back (or side) while you
are being monitored may be uncomfortable or painful if you are having labor
contractions. The belts holding the monitors in place may feel tight.
You may be able to change positions or move around more during internal
electronic fetal heart monitoring than during external monitoring.
Placing the internal monitor into your uterus may be mildly
Studies show that electronic fetal monitoring
may be linked to an increase in cesarean deliveries and in the use of a vacuum
or forceps during delivery.1
There is a
slight risk of infection for your baby when internal monitoring is done.
Electronic fetal heart monitoring is
done during pregnancy, labor, and delivery to keep track of the heart rate of
your baby (fetus) and the strength and duration of the
contractions of your
uterus. The results of electronic fetal heart
monitoring are usually available immediately.
Your baby's heart rate is 110 to 160 beats per
Your baby's heart rate increases (accelerates) when he
or she moves and when your uterus contracts.
Your baby's heart rate drops during a contraction but
rapidly returns to normal after the contraction is over.
Uterine contractions during labor are strong and
Your baby's heart rate is less than 110 beats per
Your baby's heart rate is more than 160 beats per
nonstress test, your baby's heart rate does not
increase by 15 beats per minute or drops far below its baseline rate
(deceleration) after he or she moves.
Uterine contractions are weak or irregular during
Reasons you may not be able to
have the test or why the results may not be helpful include:
American College of Obstetricians and Gynecologists
(2009). Intrapartum fetal heart rate monitoring: Nomenclature, Interpretation, and General Management Principles. ACOG Practice Bulletin No. 106.
Obstetrics and Gynecology, 114(1):
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 FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
Current as of:
June 4, 2014
Sarah Marshall, MD - Family Medicine & William Gilbert, MD - Maternal and Fetal Medicine
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