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 a clotting disorder, a blood disorder, 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)
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 attached to belt. It’s an external fetal heart rate monitor. The provider puts it over the baby's heartbeat.
The baby's 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 baby's heart rate goes up 2 or more times in the testing period.
Nonreactive. There is no change in the baby's 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 you will get the results
Who to call after the test or procedure if you have questions or problems
How much you will have to pay for the test or procedure