Prenatal Testing Basics: Non-Stress Test

What it is, who has it, when, why, and what it tells you.

By the editors of Parents magazine

When is the test taken?

The non-stress test is usually taken during the third trimester, typically within one month of the expectant mother's due date.

Who needs to take the test, and why?

The non-stress test is often used when a pregnancy is considered high risk or has lasted past the due date, or when an ultrasound shows that uterine conditions may not be optimal. The test allows your healthcare provider to evaluate your baby's well-being by measuring changes in his heart rate.

What's involved?

During the test, you'll be asked to rest quietly for about twenty minutes on an examining table or in a reclining chair. A belt equipped with ultrasound transducers will be strapped around your abdomen. Through it, the baby's heart rate will be measured as a response to its own movements (the heartbeat usually speeds up when the baby moves). If the baby isn't moving much, it may be asleep and will be wakened by a gentle nudge through the abdomen or with a buzzer. The test is painless for mother and baby.

When are test results available, and how are they interpreted?

Non-stress test results are available immediately. Results are considered normal, or "reactive," if the fetal heart rate accelerates normally in response to movement. A "non-reactive" test means that the heart rate does not respond as expected. If that's the case, you may be asked to take follow-up tests, such as a contraction stress test. This needn't be cause for alarm -- perfectly healthy babies sometimes have non-reactive tests. If your practitioner feels that uterine conditions for your baby aren't what they should be, you may be advised to deliver early by inducing labor.