Checking your baby's well being

Non-Stress Test

With movement, the fetus will increase its heart rate and should maintain this increase for several seconds. If the movement stresses the fetus, the heart rate will drop quickly. This test monitors the acceleration of heart rate and whether the fetus becomes stressed or not. The mother is asked to lay down for 20-40 minutes while the fetal heart rate is recorded with a disc-shaped Doppler ultrasound strapped around her abdomen, similar to the Doppler equipment used to listen to the fetal heart rate. The Doppler is attached to a monitor that graphs the fetal heart rate. She will report each time she feels the baby move by pressing a button that makes an arrow on the graph. A normal fetus will raise its heart rate at least 15 beats whenever it moves. If the baby shows two accelerations in heart rate lasting at least 15 seconds during the 20-minute test, it is read as normal or “reactive.”

A reactive non-stress test (NST) is a reassuring sign of fetal well being. It is important to note that the gestational age of the fetus can also affect the outcome of the NST. Only 50% of NSTs are reactive in weeks 24 –32 of pregnancy. If the heart rate does not accelerate with movement or another 20 minutes of observation fails to meet the criteria, and then the non-stress test is considered “non-reactive.” Often a Biophysical Profile (BPP) will be recommended to further evaluate the well being of the baby.