Health & Pregnancy

Why It Is Done

External fetal heart monitoring is done to:

• Keep track of your baby's heart rate.
• Measure how often you have a contraction and how long your contractions last during labor and delivery.
• Find out whether you are having preterm labor.
• Check on your baby's health if problems are suspected. External fetal heart monitoring will be done during a nonstress test to check your baby's heart rate while at rest and while moving. If your baby does not move during this test, more testing will be needed.
• Check on your placenta to make sure that it is giving your baby enough oxygen. A contraction stress test that shows that your baby is not getting enough oxygen helps your doctor make decisions about the safest delivery method. If the test shows that your baby may be in danger, your doctor may recommend starting (inducing) labor early or may talk to you about doing a cesarean section (C-section).
• Check your baby's health if your baby has not been growing normally (delayed fetal growth) or if you have diabetes, high blood pressure (hypertension), or are over 41 weeks pregnant.

Internal fetal heart monitoring is done to:

• Find out if the stress of labor is threatening your baby's health.
• Measure the strength and duration of your labor contractions.

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.

External monitoring

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.