A nonstress test is a type of test done during pregnancy. It measures the heart rate of the unborn baby (fetus) in response to its movements. In most cases, the heart rate of a healthy baby increases when the baby moves. The nonstress test is usually done in the last trimester of pregnancy.
Your healthcare provider may advise a nonstress test in any of these cases:
- Your pregnancy is high risk because you have thyroid, kidney, or heart disease, diabetes, or high blood pressure
- Your baby is moving less than usual, has slow growth, has too much or too little amniotic fluid, or is overdue
- You had a stillborn baby in the past
- Your blood is Rh negative
- You have a multiple pregnancy (twins or more) with a shared placenta
There are no risks to either the mother or baby during a nonstress test.
You don’t need to do any special preparation before the test.
The test may be done in a special prenatal testing area of the hospital. Or it may be done in your healthcare provider’s office.
The procedure may vary, but a typical nonstress test may go like this:
- You will lie in a comfortable position on an exam table. The provider puts gel on your belly. He or she puts a belt around your belly. A device called a transducer is on the belt. It’s an external fetal heart rate monitor. The provider puts it over the fetal heart beat.
- The fetal heart rate is recorded on a monitor and on a paper printout.
- You will be asked to push a button on the monitor each time you feel your baby move.
- This testing usually lasts for 20 to 40 minutes.
In some cases, the testing occurs during a baby’s sleep cycle, when there is little fetal movement. A special sound (acoustic) device may be used to awaken the baby. It is placed against the mother’s belly and makes a noise like a buzzer. This is not harmful to the baby. But it may help a sleepy baby become more active. Your baby may also awaken if you eat or drink.
The provider will remove the belt and transducer and wipe off the gel. You will be told the results of the test.
Test results of the nonstress test may be:
- Reactive (normal). The fetal heart rate goes up 2 or more times in the testing period.
- Nonreactive. There is no change in the fetal heart rate when the baby moves. This may mean you will need other tests.
A nonreactive nonstress test doesn’t always mean your baby has a problem. The baby may simply be asleep. Or it may be nonreactive because the baby is immature. It’s common for preterm babies to have nonreactive nonstress tests, especially before 28 weeks. Your healthcare provider will tell you if you need other prenatal testing.
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
- What results to expect and what they mean
- The risks and benefits of the test or procedure
- What the possible side effects or complications are
- When and where you are to have the test or procedure
- Who will do the test or procedure and what that person’s qualifications are
- What would happen if you did not have the test or procedure
- Any alternative tests or procedures to think about
- When and how will you get the results
- Who to call after the test or procedure if you have questions or problems
- How much will you have to pay for the test or procedure