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Fetal Heart MonitoringControl externo e interno de la frecuencia cardíaca fetal

Fetal Heart Monitoring

What is fetal heart monitoring?

Fetal heart rate monitoring measures the fetus’ heart rate and rhythm. This lets your healthcare provider see how your fetus is doing.

Your healthcare 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 the fetus responds to conditions in the uterus. An abnormal fetal heart rate may mean that the fetus is not getting enough oxygen or that there are other problems.

There are 2 ways to do fetal heart monitoring, external and internal:

External fetal heart monitoring

This method uses a device to listen to and record the fetal heartbeat through your belly (abdomen). One type of monitor is a Doppler ultrasound device. It’s often used during prenatal visits to count the fetal heart rate. It may also be used to check the fetal heart rate during labor. The healthcare provider may also check the fetal heart rate continuously during labor and birth. To do this, the ultrasound transducer is fastened to your belly. It sends the sounds of the fetal heart to a computer. The rate and pattern of the fetal heart rate are shown on a screen and printed on paper.

Internal fetal heart monitoring

This method uses a transducer put on your fetus’ scalp. The wire runs from the fetus through  your cervix. It is connected to the monitor. This method gives better readings because things like movement do not affect it. But it can only be done if the fluid-filled sac that surrounds the fetus during pregnancy (amniotic sac) has broken and the cervix is opened. Your doctor may use internal monitoring when external monitoring is not giving a good reading. Or the provider may use this method to watch the fetus more closely during labor.

During labor, your healthcare provider will watch your uterine contractions and the fetal heart rate. Your provider will note how often you are 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, he or she will put a thin tube (catheter) through your cervix and into the uterus. The catheter will send uterine pressure readings to a monitor.

Why might I need fetal heart monitoring?

Fetal heart rate monitoring is used in nearly every pregnancy at prenatal visits. It is done to check on how the fetus is doing and to look for any problems. Fetal heart rate monitoring is especially helpful if you have a high-risk pregnancy. Your pregnancy is high risk if you have diabetes or high blood pressure. It is also high risk if your fetus is not developing or growing as it should.

Fetal heart rate monitoring may be used to check how preterm labor medicines are affecting the fetus. These are medicines are used to help keep labor from starting too early.

Fetal heart rate monitoring may be used in other tests, including:

  • Non-stress test. This measures the fetal heart rate as your fetus moves.
  • Contraction stress test. This measures fetal heart rate along with uterine contractions. Contractions are started with medicine or other methods.
  • A biophysical profile (BPP). This test combines a non-stress test with ultrasound.

Things that may affect the fetal heart rate during labor:

  • Uterine contractions
  • Pain medicines or anesthesia given to you during labor
  • Tests done during labor
  • Pushing during the second stage of labor

Your healthcare provider may have other reasons to use fetal heart rate monitoring.

What are the risks of fetal heart monitoring?

Radiation is not 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 fetus’ scalp or other body part.

You should not have internal fetal heart rate monitoring if you are HIV positive. This is because you may pass the infection on to the fetus.

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 rate monitoring less accurate. These include:

  • Obesity of the mother
  • Position of the fetus or mother
  • Too much amniotic fluid (polyhydramnios)
  • Cervix is not dilated or the amniotic sac is not broken. Both of these need to happen  to do internal monitoring

How do I get ready for fetal heart monitoring?

  • Your healthcare provider will explain the procedure to you. Ask him or her any questions you have about the procedure.
  • 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.
  • The consent form for fetal heart monitoring may be included as part of the general consent for labor and birth.
  • Tell your healthcare provider if you are sensitive to or are allergic to any medicines, latex, tape, or anesthesia.
  • 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 fetus more active.
  • The amniotic sac must be broken and your cervix must be dilated several centimeters before the internal device can be put in place.
  • Follow any other instructions your provider gives you to get ready.

What happens during fetal heart monitoring?

You may have fetal heart rate 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 health care provider's practices.

Generally, fetal heart rate monitoring follows this process:

External fetal heart monitoring

  1. 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.
  2. You will lie on your back on an exam table.
  3. The healthcare provider will put a clear gel on your abdomen.
  4. The provider will press the transducer against your skin. The provider will move it around until he or she finds the fetal heartbeat. You will be able to hear the sound of the fetal heart rate with Doppler or an electronic monitor.
  5. During labor, the provider may check the fetal heart rate at intervals or nonstop, based on your condition and the condition of your baby.
  6. 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.
  7. The provider will record the fetal heart rate.  With continuous monitoring, the fetal heart pattern will be displayed on a computer screen and printed on paper.
  8. You may not be able to get out of bed with nonstop external fetal heart rate monitoring.
  9. Once the procedure is done, the provider will wipe off the gel.

Internal fetal heart monitoring

  1. You will be asked to remove your clothes and put on a hospital gown.
  2. You will lie on a labor bed. Your feet and legs will be supported as for a pelvic exam.
  3. Your healthcare provider will do a vaginal exam with a gloved hand to see how far you are dilated. This may be slightly uncomfortable.
  4. If the amniotic sac is still intact, your healthcare provider may break open the membranes with a tool. You will feel warm fluid coming out of your vagina.
  5. Your healthcare provider will feel the part of the fetus at the cervical opening with gloved fingers. This is usually the fetus’ head.
  6. The provider will put a thin tube (catheter) into your vagina. He or she will put a small wire at the end of the catheter on the fetus’ scalp. He or she will gently turn it on the fetus’ skin.
  7. The provider will remove the catheter and leave the wire in place on the fetus’ scalp.
  8. The provider will connect the wire to a monitor cable. He or she will keep it in place with a band around your thigh.
  9. You may not be able to get out of bed with nonstop internal fetal heart rate monitoring.
  10. Once the baby is born, the provider will remove the wire.

What happens after fetal heart rate monitoring?

You do not 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 rate monitoring, your healthcare provider will check your baby’s scalp for infection, bruising, or a cut. The provider will clean the site with an antiseptic.

Your healthcare provider may give you other instructions, based on your situation.

Next steps

Before you agree to the test or the procedure make sure you know:

  • The name of the test or procedure
  • The reason you are having the test or procedure
  • The risks and benefits of the test or procedure
  • When and where you are to have the test or procedure and who will do it
  • When and how will you get the results
  • How much will you have to pay for the test or procedure

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