What is a nonstress test (NST)?

A nonstress test (NST or fetal nonstress test) is a pregnancy screening that measures fetal heart rate and reaction to movement. Your pregnancy care provider performs a nonstress test to make sure the fetus is healthy and getting enough oxygen. It’s safe and painless, and gets its name because it puts no stress (nonstress) on you or the fetus.

During an NST, your provider is watching for the fetus’ heart rate as it moves. Just as your heart rate increases when you run, its heart rate should increase when it moves or kicks.

If the fetus’ heart rate doesn’t react to movement or it isn’t moving at all, it doesn’t mean something is wrong. It could mean the fetus doesn’t have enough oxygen, but this isn’t always the case. Your pregnancy care provider uses the results of a nonstress test to decide if they need to order additional testing or if inducing labor is necessary.

Why do you need a nonstress test during pregnancy?

Not everyone needs a nonstress test. Your pregnancy care provider orders a nonstress test to check fetal health. Some reasons they may do this include:

You’re past your due date: You’re overdue once your pregnancy is past 40 weeks. Being past your due date can cause complications, even if your pregnancy is low-risk and healthy.

Your pregnancy is high-risk: Reasons for a high-risk pregnancy could include chronic medical conditions like diabetes or high blood pressure. It means your provider monitors you and the fetus more closely during pregnancy.

You don’t feel the fetus moving as much: If you feel a decrease in the amount the fetus moves, your provider may order an NST.