Fetal Heart Monitoring
What is fetal heart monitoring?
Fetal heart monitoring measures the heart rate and rhythm of your baby (fetus). This lets your healthcare provider see how your baby is doing.
Your provider may do fetal heart monitoring during late pregnancy and labor. The average fetal heart rate is between 110 and 160 beats per minute. It can vary by 5 to 25 beats per minute. The fetal heart rate may change as your baby responds to conditions in your uterus. An abnormal fetal heart rate may mean that your baby isn't getting enough oxygen or that there are other problems.
There are two ways to do fetal heart monitoring, external and internal.
External fetal heart monitoring
This method uses a device to listen to and record your baby’s heartbeat through your belly (abdomen). One type of monitor is a Doppler ultrasound device. It’s often used during prenatal visits to count the baby’s heart rate. It may also be used to check the fetal heart rate during labor. The healthcare provider may also check your baby’s heart rate continuously during labor and birth. To do this, the ultrasound probe (transducer) is fastened to your belly. It sends the sounds of your baby’s heart to a computer. The rate and pattern of your baby’s heart rate are shown on a screen and may be printed on paper.
Internal fetal heart monitoring
This method uses a thin wire (electrode) put on your baby’s scalp. The wire runs from the baby through your cervix. It's connected to the monitor. This method gives better readings because things like movement don’t affect it. But it can only be done if the fluid-filled sac that surrounds the baby during pregnancy (amniotic sac) has broken and the cervix is opened. Your provider may use internal monitoring when external monitoring isn't giving a good reading. Or your provider may use this method to watch your baby more closely during labor.
During labor, your provider will watch your uterine contractions and your baby’s heart rate. Your provider will note how often you're having contractions and how long each lasts. Because the fetal heart rate and contractions are recorded at the same time, these results can be looked at together and compared.
Your provider may check the pressure inside your uterus while doing internal fetal heart monitoring. To do this, they will put a thin tube (catheter) through your cervix and into your uterus. The catheter will send uterine pressure readings to a monitor.
Why might I need fetal heart monitoring?
Fetal heart monitoring is especially helpful if you have a high-risk pregnancy. For example, your pregnancy is high risk if you have diabetes or high blood pressure. It's also high risk if your baby isn't developing or growing as it should.
Fetal heart monitoring may be used to check how preterm labor medicines are affecting your baby. These medicines are used to help keep labor from starting too early.
Fetal heart monitoring may be used in other tests, including:
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Nonstress test. This measures the fetal heart rate as your baby moves.
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Contraction stress test. This measures fetal heart rate along with uterine contractions. Contractions are started with medicine or other methods.
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Biophysical profile. This test combines a nonstress test with ultrasound.
Things that may affect the fetal heart rate during labor:
Your healthcare provider may have other reasons to use fetal heart monitoring.
What are the risks of fetal heart monitoring?
Radiation isn't used for this test. The transducer usually causes no discomfort.
You may find the elastic belts that hold the transducers in place slightly uncomfortable. These can be readjusted as needed.
You must lie still during some types of fetal heart rate monitoring. You may need to stay in bed during labor.
With internal monitoring, you may have some slight discomfort when the electrode is put in your uterus.
Risks of internal monitoring include infection and bruising of your baby’s scalp or other body part.
Note: You should not have internal fetal heart rate monitoring if you're HIV positive. This is because you may pass the infection on to your baby.
You may have other risks depending on your specific health condition. Be sure to talk with your provider about any concerns you have before the procedure.
Certain things may make the results of fetal heart monitoring less accurate. These include:
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Obesity of the mother
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Position of the baby or mother
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Too much amniotic fluid (polyhydramnios)
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Cervix isn't dilated or the amniotic sac isn't broken. Both of these need to happen to do internal monitoring
How do I get ready for fetal heart monitoring?
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Your healthcare provider will explain the procedure to you. Ask them any questions you have about the procedure.
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You may be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if anything is not clear.
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The consent form for fetal heart monitoring may be included as part of the general consent for labor and birth.
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Tell your healthcare provider if you are sensitive to or are allergic to any medicines, latex, tape, or anesthesia.
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If fetal heart rate monitoring is done along with another monitoring test, you may be asked to eat a meal before the test. This can help make your baby more active.
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The amniotic sac must be broken and your cervix must be dilated several centimeters before the internal device can be put in place.
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Follow any other instructions your healthcare provider gives you to get ready.
What happens during fetal heart monitoring?
You may have fetal heart monitoring in your healthcare provider's office or as part of a hospital stay. The way the test is done may vary depending on your condition and your provider's practices.
Generally, fetal heart monitoring follows this process:
External fetal heart monitoring
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Depending on the type of procedure, you may be asked to undress from the waist down. Or you may need to remove all of your clothes and wear a hospital gown.
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You'll lie on your back on an exam table.
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The provider will put a clear gel on your abdomen.
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The provider will press the transducer against your skin. The provider will move it around until they find the fetal heartbeat. You'll be able to hear the sound of the fetal heart rate with Doppler or an electronic monitor.
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During labor, the provider may check the fetal heart rate at intervals or nonstop, based on your condition and the condition of your baby.
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For continuous electronic monitoring, the provider will connect the transducer to the monitor with a cable. A wide elastic belt will be put around you to hold the transducer in place.
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The provider will record the fetal heart rate. With continuous monitoring, the fetal heart pattern will be displayed on a computer screen and can be printed on paper.
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You may not be able to get out of bed with nonstop external fetal heart rate monitoring.
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Once the procedure is done, the provider will wipe off the gel.
Internal fetal heart monitoring
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You'll be asked to remove your clothes and put on a hospital gown.
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You'll lie on a labor bed. Your feet and legs will be supported as for a pelvic exam.
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Your healthcare provider will do a vaginal exam with a gloved hand to see how far you're dilated. This may be slightly uncomfortable.
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If the amniotic sac is still intact, your provider may break open the membranes with a tool. You will feel warm fluid coming out of your vagina.
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Your provider will feel the part of the baby at the cervical opening with gloved fingers. This is usually the baby’s head.
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The provider will put a thin tube (catheter) into your vagina. They will put a small wire at the end of the catheter on the baby’s scalp. The provider will gently turn it on the baby’s skin.
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The provider will remove the catheter and leave the wire in place on the baby’s scalp.
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The provider will connect the wire to a monitor cable. They will keep it in place with a band around your thigh.
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You may not be able to get out of bed with nonstop internal fetal heart rate monitoring.
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Once the baby is born, the provider will remove the wire.
What happens after fetal heart monitoring?
You don't need any special care after external fetal heart monitoring. You may go back to your normal diet and activity unless your healthcare provider tells you otherwise.
After internal fetal heart monitoring, your provider will check your baby’s scalp for infection, bruising, or a cut. The provider will clean the site with an antiseptic.
Your provider may give you other instructions, based on your situation.
Next steps
Before you agree to the test or procedure make sure you know:
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The name of the test or procedure
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The reason you are having the test or procedure
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What results to expect and what they mean
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The risks and benefits of the test or procedure
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What the possible side effects or complications are
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When and where you are to have the test or procedure
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Who will do the test or procedure and what that person’s qualifications are
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What would happen if you did not have the test or procedure
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Any alternative tests or procedures to think about
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When and how you will get the results
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Who to call after the test or procedure if you have questions or problems
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How much you will have to pay for the test or procedure