Nonstress Test

What is a nonstress test?

A nonstress test uses fetal monitoring to check the health of an unborn baby. An external fetal monitor is attached with belts to the mother’s abdomen (belly) and records the baby's heart rate. Your healthcare provider will watch how the baby’s heart rate changes when the baby moves. Normally, when a healthy baby moves, the baby's heart rate goes up.

When is it used?

You may have this test if:

• You have a high-risk condition, such as high blood pressure or a baby that is not growing properly.
• You had problems in a previous pregnancy, such as a baby who died at birth.
• You have noticed that your baby is not moving as much as he or she used to.
• You are past your due date.
• You have a disease, such as diabetes.
• You are pregnant with more than 1 baby (for example, twins or triplets).
• You have too little or too much amniotic fluid.

The test is most reliable when it is done:

• In the last 6 to 8 weeks of pregnancy.
• At the time of day when the baby is most active (1 to 2 hours after you eat a meal).

You may need to have several nonstress tests to show the baby's well-being over time.

How do I prepare for this test?

• Pregnant women should not smoke, but if you do smoke, do not smoke for at least 4 hours before the test. Smoking can decrease your baby’s movements.
• Eat a full breakfast or lunch before the test unless you get different instructions from your provider.

What happens during the test?

An external fetal monitor is strapped to your abdomen. The monitor will record the baby's heart rate. You may be given a button to push when you feel the baby move.

The results of the test are classified as follows:

• Reactive: The baby moves 2 or more times in 20 minutes. During at least 2 of these movements, the baby’s heart rate increases by 15 beats a minute and stays increased for at least 15 seconds. Reactive results of this test are a sign that the baby is probably doing well.
• Nonreactive: Either the baby does not move or the heart rate does not rise enough during movements.

Often a test is nonreactive because the baby is not moving enough to get good readings. The test might be done again when the baby is more active. Sometimes drinking a glass of juice, such as cranberry or orange juice, will help the baby become more active. A device that makes a noise like a buzzer may be placed against your abdomen to try to make the baby move.

If second test is nonreactive, an ultrasound test called a biophysical profile may be done. If the well-being of the baby is still not clear, a contraction stress test may be done for certain reasons.

What happens after the procedure?

You may need to repeat the test 3 to 7 days later. You may need to have the test several times.

Your healthcare provider may recommend other tests, such as a contraction stress test or biophysical profile.

In some cases your provider may decide that the baby should be delivered early.

What are the benefits of this test?

• If the test result is normal (reactive), it can reassure you and your healthcare provider that the baby is probably doing well.
• If the test result is abnormal (nonreactive), it helps you and your provider know that the baby may have problems. As a result of this and other tests, your provider may decide it is best to deliver the baby before labor starts.

What are the risks of this test?

The test does not pose any risks to you or the baby.