This is not a routine test. A doctor will use this any time after 26-28 weeks for high-risk pregnancies to ensure that the baby is getting enough oxygen and is not in any kind of distress. This test is simple and non invasive. It is called “non stress” because no/minimal stress is placed on the baby.
A doctor may also use this also for low-risk pregnancies, if the mothers report lack of foetal movement, or if they are overdue.
The NST can help a doctor make sure that the baby is receiving enough oxygen and is responding to stimulation. Usually a healthy baby moves a lot. Even if the baby does not respond as expected, it does not confirm that the baby is in danger. In those cases, further testing like the Biophysical Profile (BPP) is conducted.
Here is how the NST is conducted
- The doctor will measure the response of the baby’s heart rate to each movement the baby makes as reported by the mother or observed by the doctor on an ultrasound screen.
- If the baby doesn't move during the test, the doctor may wake the baby by a buzzer or you might be asked to drink a sweet drink to stimulate the baby.
- If the baby does not move, it signals to the doctor that something might be wrong and further testing is required.
Sometimes, a biophysical profile (BPP) is done to determine problems with the baby. In this the doctor combines inputs from many other sources as well. The sources for a BPP include:
- Ultrasound to determine the amniotic fluid and the growth of the fetus
- Physical examination of baby’s breathing, baby’s heart rate response to movement
- Mother provides information about the baby’s movement and kicks