Sometimes, we need to test the health of your unborn baby. The Prenatal Diagnosis Center offers the following tests:
We use a machine known as a fetal monitor to do a non-stress test. A non-stress test (NST) looks at your baby's heart rate over time (usually 20 to 30 minutes, but sometimes up to an hour). The monitor has two sensors that are placed on your belly with two belts that go around your waist. One sensor detects any contractions you may be having, even those you might not even feel. The other sensor tracks your baby's heart rate, which you can hear. The information is displayed on graph on paper or on a computer screen. During the test, you'll be comfortable in a reclining chair.
One of our nurses will watch the heart rate during the test to see how your baby is doing and make sure the heart rate increases when your baby moves.
- A NST is considered reassuring if the fetal heart rate increases at least 15 beats per minute over the baseline (between 120 and 160 beats per minute), lasting at least 15 seconds, within a 20-minute timeframe. This is called a "reactive NST."
- If these accelerations do not occur, the test is said to be "nonreactive." Although a reactive NST is a good sign, a nonreactive NST does not mean there is something wrong with your baby. The baby might be sleeping or a more in-depth NST or a biophysical profile might be needed.
Biophysical profile and amniotic fluid index
A biophysical profile (BPP) is an ultrasound exam that monitors the movement, body tone and breathing efforts of your baby. Each of these four measurements is given a score of zero or two points, and the scores added up. If the BPP is used with a NST and the NST was "reactive," another two points is added.
- A high score of 8 to 10 means your baby is in good condition inside the womb.
- A low score of 0 to 4 usually means that your baby needs to be delivered.
- A score of 6 usually requires a repeat test within 24 hours.
The amniotic fluid index (AFI) is an ultrasound exam that measures the amount of amniotic fluid around your baby.
We may need to measure the pockets of amniotic fluid for several reasons. Perhaps you are past your due date or you have a history of water breaking too early in a pregnancy.
The BPP and AFI testing takes approximately one hour and is not uncomfortable.