How to Read an NST

By Catherine Chase
An NST is a non-invasive test that does not harm the baby.
An NST is a non-invasive test that does not harm the baby.

Your doctor may recommend a non-stress test during the last trimester of your pregnancy. This test may be helpful for babies who are overdue, smaller or less active than usual, or if you have other conditions such as gestational diabetes. This painless test measures your baby's heartbeats and movements. It typically takes about 30 minutes to complete. In addition to reading the test results, rely on your doctor for a definitive interpretation of the NST results.

Ask the doctor for the paper strip from the monitor, which records your baby's heartbeats. Look for areas of accelerated heartbeats.

Count the number of accelerated heartbeats in one area and compare it to the time the acceleration occurred. If your baby's heartbeat accelerated at least 15 beats per minute above his baseline heartbeat for at least 15 seconds, this indicates a reactive non-stress test result.

Calculate the number of times this acceleration occurred. A typical reactive NST indicates at least two areas of accelerated heartbeats that last for at least 15 seconds each time.

Interpret the NST results as non-reactive if your baby's heartbeat rarely accelerated. In some cases, the heartbeat may not change at all, or it may change very little.

Ask the doctor to run the test again if the results indicate a non-reactive NST. This is optional; a non-reactive NST does not necessarily mean that your baby has a medical problem. If he was asleep for the test, the doctor may use a harmless buzzer sound to wake him up before running the test again. Otherwise, your doctor may recommend an ultrasound, a contraction stress test or a biophysical profile. These tests assess the well-being of your baby, such as his ability to move his chest muscles and the amount of amniotic fluid surrounding him.

Tip

A reactive non-stress test indicates that your baby receives sufficient nutrition, moves around well and is generally healthy. A non-reactive test result does not necessarily indicate poor health; it means that the baby's heartbeat did not increase.

About the Author

Catherine Chase is a professional writer specializing in history and health topics. Chase also covers finance, home improvement and gardening topics. She holds a Bachelor of Arts in American studies from Skidmore College.