Electronic Fetal Heart Monitoring
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.
Two 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 during labor.
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 a chart.
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 a fetal ultrasound to evaluate the amount of your amniotic fluid.
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 vaginal delivery.
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.
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 contractions.
Why It Is Done
External fetal heart monitoring is done to:
Internal fetal heart monitoring is done to:
How To Prepare
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 are having a contraction stress test, you may be asked to not eat or drink for 4 to 8 hours before the test.
If you smoke, you will be asked to stop smoking for two hours before the external monitoring test because smoking decreases your baby's activity.
How It Is Done
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 table 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.
For a 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 a contraction stress test, the sensors are placed on your belly. After about 20 minutes of monitoring, uterine contractions are started (induced). To start contractions, you may be instructed to stimulate your nipples or you may be given a medication called oxytocin (such as Pitocin) in a vein (intravenous, or IV). If oxytocin is given, it will be increased gradually until you have 3 contractions in 10 minutes. Changes in your baby's heart rate in response to your contractions are measured.
For internal monitoring, you will usually lie on a table 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 indicate or print out a record of your baby's heart rate as well as the strength and duration of your uterine contractions.
How It Feels
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 uncomfortable.
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.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
What To Think About
Other Places To Get Help
eMedicineHealth Medical Reference from Healthwise
To learn more visit Healthwise.org
© 1995-2012 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
Find out what women really need.