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.
The fetus measures small for its gestational age: If your provider believes the fetus isn’t growing properly, they may order an NST earlier in your pregnancy.
You’re expecting multiples: If you’re having twins, triplets or more, your pregnancy is at risk for complications.
You’re Rh negative: If the fetus is Rh positive, your body will make antibodies against their blood. This can cause serious complications.
When in pregnancy are nonstress tests done?
A nonstress test typically happens after 28 weeks of pregnancy. This is when fetal heart rate starts reacting to movements. Your pregnancy care provider orders an NST when they feel it’s necessary to check on the fetus’ health.
What is the difference between a nonstress test and a stress test?
A nonstress test measures the fetus’ heart rate to see if it changes when it moves or during uterine contractions (when muscles in your uterus tighten). An NST places no extra stress on you or the fetus. You wear monitors around your belly and lay down for the test.
A stress test measures your heart rate, blood pressure and oxygen levels under stress. It usually involves walking on a treadmill or pedaling on a stationary bike with monitors attached to your chest. The test helps your provider determine how well your heart responds when it’s working hard or under stress.
Post time: Aug-28-2023
