There are a number of third trimester tests that can be performed to assess the health of an unborn baby. These tests carry no risk to the baby. These tests include the non-stress test (NST), the biophysical profile, and Doppler evaluation of blood circulation in the umbilical cord and baby.
This test involves sitting in an easy chair and having belts put around the abdomen that secure monitors for fetal heart rate and contraction monitoring. The heart rate is then evaluated for variability in the baseline (fetal heart rate should vary over time and should not be constant) and for accelerations in the fetal heart rate with movement. Presence of variability and accelerations are signs that the baby is healthy. Absence of these factors does not mean that there is a problem, but further evaluation, usually with a biophysical profile, is indicated. The test is called a non-stress test because in the past prior to ultrasound, the other test to assess the health of the baby was called a contraction stress test. This test involved causing contractions with medication and seeing how the baby responded to the stress of the contractions. This test currently is rarely used since better, less invasive testing is available with ultrasound.
This test combines the non-stress test with four other tests of fetal health assessed with ultrasound. These tests include fetal breathing motions, fetal body movement, fetal muscle tone and amniotic fluid volume. This test may take 30 minutes or longer to perform. A score of 0 or 2 is given for each of the five parameters and a total score of 8 or 10 is consistent with a healthy baby. A score of 6 is usually considered equivocal. A score of 4 or less is usually concerning but can also be seen in healthy babies who are in a prolonged sleep cycle or have exposure to certain medications like narcotics.
Doppler evaluation of fetal circulation
With state-of-the-art ultrasound equipment, blood flow in the umbilical cord, fetal brain, fetal liver, and other fetal blood vessels can be assessed. This type of testing is especially useful in evaluating babies with intrauterine growth restriction (poor growth of the baby) and those at risk for being anemic. Different patterns of blood flow are seen when the baby is doing well compared to when the baby is compensating for less than optimal amounts of oxygen and nutrients. Also signs of decompensation for lack of adequate oxygen and nutrients can be detected with Doppler studies.
There are many indications for antepartum testing of the baby’s health. Common indications include poor growth of the baby, maternal medical problems such as high blood pressure or diabetes, and pregnancy complications such as preeclampsia, twins or going past the due date. Frequency of testing is usually once or twice a week, depending upon indication.
All tests described above are available at Adventist Maternal Fetal Medicine Center. The physicians at Adventist Maternal Fetal Medicine Center have received additional, specialized training in performing and interpreting tests used to assess fetal health and well-being.