Non-Stress Test for Fetal Well-Being in Late Pregnancy

Toward the end of your pregnancy, your doctor may schedule regular non-stress tests (NST) to monitor the health of your baby. This common and non-invasive test is often performed between 38 weeks and 42 weeks gestation to ensure fetal well-being, but may be ordered earlier if the doctor deems it necessary.

Non-stress tests are typically performed in your doctor's office and take between 20 minutes and 40 minutes to complete. Since you will be hooked up to a machine for that time, be sure to use the lavatory beforehand.

Why You Should Do an NST

A simple and painless procedure, a non-stress test is often used in cases where the mother is going past her assigned due date or during a high-risk pregnancy. For example, mothers who have had previously problematic pregnancy or have pre-existing or gestational diabetes may undergo NSTs more frequently.

The test monitors accelerations and de-accelerations of the baby's heart rate, as well as any contractions you may be having. If you are concerned that your baby isn't moving as much, your doctor may order this test.

How an NST Is Done

The non-stress test is usually done in your practitioner's office. You will sit in a chair or lie on a table with fetal monitoring equipment hooked to your belly. The monitor will record your baby's heart rate in conjunction with any uterine activity. You may be asked to press a button when the baby moves so that the heart rate can be seen in relation to that movement.

When Is a Test Done?

This test is most frequently done between weeks 38 and 42, however, it can be used as early as the beginning of the third trimester. In many high-risk pregnancies, NSTs are done twice a week, but the test can be performed as often as needed—including daily. The frequency will depend on the reason it is ordered by your practitioner.

Results

Non-stress tests are rated as reactive and non-reactive. The test is reactive if the baby's heart beats faster when she moves. A non-reactive result means that the heart does not beat faster upon movement, or that the baby isn't moving much.

Sometimes little ones don't move during the testing, which may just mean your baby is asleep. If this is the case, the mother is offered a cold drink of water or something sweet to perk the baby up. If this doesn't cause the baby to move you may be asked to poke your baby or the technician will use a loud sound to startle the baby into moving.

Risks Involved

A non-stress test is not considered a risky test. It is non-invasive and does not require blood samples or invasive exams. The biggest risk is a misinterpretation of the data. If you have concerns, be sure to talk to your practitioner about them before undergoing the test. They can reassure you about how they are working to minimize the risks to you and your baby.

Alternatives

There are two alternatives to the non-stress test: Stress testing or biophysical profile. And keeping in mind that alternatives aren't always desirable, there is also the option of delaying the non-stress test or choosing not to have the non-stress test.

After an NST

If the baby is still not as responsive as they would like you may either go to a biophysical profile, a stress test, or even induction if you are close to or past your due date.

A Word From Verywell

How and why this test is done can also vary from practitioner to practitioner. If you have questions about the test, when it's done, how often it's done, or who does it, be sure to speak up. The goal of the test is to ultimately reassure you and your practitioners that everything is going well. If you are not feeling that reassurance, be sure to speak up and ask questions.