What Is a Nonstress Test? A nonstress test monitors an unborn baby's heart rate for 20 to 30 minutes to see if it changes as the fetus moves and during contractions. It is called "nonstress" because doing it places no stress on the fetus. Why Are Nonstress Tests Done? A nonstress test (NST) is usually done when a health care provider wants to check on the health of the fetus, such as in a high-risk pregnancy or when the due date has passed. The test checks to see if the baby responds normally to stimulation and is getting enough oxygen. A baby that doesn't respond isn't necessarily in danger, though more testing might be needed. Sometimes, a biophysical profile (BPP) is done, which includes an ultrasound and an NST. A BPP examines a baby's breathing, movement, amount of amniotic fluid, and tone, in addition to the heart rate response. Should I Have a Nonstress Test? Your health care provider may recommend this if you have a high-risk pregnancy, if there are concerns during your pregnancy, or if you have a low-risk pregnancy but are past your due date. What Happens During a Nonstress Test? You'll wear two monitors (one tracks the baby's heartbeat and movement, and the other records contractions) while lying on your left side. A technician monitors the fetal heart rate during each movement on a screen while your contractions are recorded on paper. If there's no movement during the test, the baby may be asleep and the technician may use a buzzer to wake the baby. You also may be asked to drink or eat to try to stimulate the baby more. When Are Nonstress Tests Done? A nonstress test is done any time after 26 to 28 weeks, depending on why it's needed. This is the age when a baby's heart rate can respond to movements by speeding up or slowing down. When Are the Results Available? Results of a nonstress test are ready immediately. Back to Articles Related Articles Prenatal Tests: First Trimester Find out what tests may be offered to you during the first trimester of pregnancy. Read More Prenatal Tests: Second Trimester Find out what tests may be offered to you during weeks 13 through 26 of pregnancy. Read More Prenatal Tests: Third Trimester Find out what tests may be offered to you during weeks 27 through 40 of pregnancy. Read More Prenatal Genetic Counseling Genetic counselors work with people who are either planning to have a baby or are pregnant to determine whether they carry the genes for certain inherited disorders. Find out more. Read More Prenatal Tests: FAQs Every parent-to-be hopes for a healthy baby, but it can be hard not to worry. Find out what tests can keep you informed of your health — and your baby's — throughout pregnancy. Read More Medical Care During Pregnancy The sooner in pregnancy good care begins, the better for the health of both moms and their babies. Here's what to expect. Read More What if My Baby Isn't Born by My Due Date? Find out what the experts have to say. Read More A Week-by-Week Pregnancy Calendar Our week-by-week illustrated pregnancy calendar is a detailed guide to all the changes taking place in your baby - and in you! Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.