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Fetal Heart Monitoring

Test Overview

Electronic fetal heart monitoring is done during pregnancy, labour, and delivery. It keeps track of the heart rate of your baby (fetus). It also shows how long each contraction of your uterus lasts. 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 labour.

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.

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 labour. It can be done only after your cervix has dilated to at least 2 centimetres (cm). And your amniotic sac must have already ruptured. 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 contractions.
  • Check on your baby's health if your doctor thinks there may be problems.
  • Check your placenta to make sure that it is giving your baby enough oxygen.
  • Check your baby's health if your baby has not been growing normally. Monitoring may also be done if you have diabetes or high blood pressure or if you are more than 41 weeks pregnant.

Internal fetal heart monitoring

This type of monitoring is done to:

  • Find out if the stress of labour is putting your baby's health at risk.
  • Measure the strength and length of your labour 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 labour 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 how long each contraction lasts. The position of the heart rate monitor may be changed now and then as your baby moves.

Internal monitoring

For internal monitoring, you will most likely 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 caesarean 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.

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 labour 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 non-stress 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 labour.

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. 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.

Credits

Current as of: October 8, 2020

Author: Healthwise Staff
Medical Review:
Sarah Marshall MD - Family Medicine
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine
William Gilbert MD - Maternal and Fetal Medicine
Femi Olatunbosun MB, FRCSC - Obstetrics and Gynecology

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