Fetal Non-Stress Test (NST)
The fetal non stress test is also known as fetal heart rate monitoring. It is a simple prenatal and non invasive test that is performed in pregnancies over 28 weeks gestation. It is used to check your baby’s health. During the test, you baby’s heart rate is monitored to see how he does during movement.
Why would an NST be performed ?
This test may be performed if you :
- are experiencing decreased fetal movement
- have pregnancy that is overdue
- have a history of pregnancy loss
- are carrying multiples and having complications
- have too much amniotic fluid (polyhydramnios) or low amniotic fluid (oligohydramnios)
- have an underlying medical condition such as high blood pressure, blood disorder, heart disease, kidney disease or thyroid disease
How is an NST performed ?
During this test, one belt is attached to the mother’s abdomen to monitor fetal heart rate and another belt is used to measure contraction. For about 20 to 30 minutes , movement , heart rate and “reactivity” of heart rate to movement is measured . If the baby does not move during this period, he could just be asleep. They may wake the baby up with a small buzzer for the remainder of the test.
Are there any risks ?
This test is non invasive and therefore poses no risk to baby and mother.
What does an NST test look for ?
The main goal of this test is to measure the heart rate of the baby in response to movement. In healthy babies, the heart rate will increase during movement and decrease during rest. The concept behind this test is that sufficient oxygen is need for fetal activity and heart rate to be within normal ranges. In cases of low oxygen level, the fetus may not respond normally. Low levels of oxygen could be caused by placenta and umbilical cord problems.
What do the results mean ?
A reactive non stress test means blood flow and oxygen to fetus is sufficient. A non reactive result may require further testing to find out if the results is really due to poor oxygenation or other reasons such as certain maternal prescription or nonprescription drugs or sleep pattern.
Monitor your baby before labor. National Library of Medicine. MedlinePlus. http://www.nlm.nih.gov/medlineplus/ency/patientinstructions/000485.htm. Accessed January 2, 2015
Non stress test. Mayo Foundation. http://www.mayoclinic.org/tests-procedures/nonstress-test/basics/definition/prc-20012971.Accessed January 2, 2015