Fetal Monitoring Before Labor
The doctor will monitor you and your baby throughout your pregnancy. Various tests can show how the baby is doing inside your uterus. These tests may be done anytime during your pregnancy, especially if you have a high-risk condition, a medical condition, or have had complications with a previous pregnancy. Sometimes a test may be repeated at intervals to show the well-being of the baby over time. Finally, tests may be done if you have reached 41- 42 weeks or are considered "overdue."
Non-Stress Test (NST)
The purpose of the NST is to confirm that the baby is healthy. It is based on the principle that the baby will have an increased heart rate when it moves.
During a non-stress test, you will be hooked up to a fetal monitor just like the one you will have when you're in labor. You will NOT be given any medication to stimulate or cause movement of the baby or contractions of the uterus.
The baby may be moving spontaneously and the test will work without any further stimulation. It may be necessary for you to encourage the baby to move by rubbing your hand over your abdomen, or the clinician may make a loud noise with a special device above the abdomen. When the baby moves, a recording is made of its heart rate.
If the heart rate goes up each time there is movement, the test will likely be considered normal. If the baby doesn't move or the heart rate does not go up when it moves, further testing may be needed to make sure the baby is not in distress. The results are usually described as "reactive" (the baby moved and the heart rate increased appropriately) or "non-reactive" (the baby did not move or the heart rate did not increase enough when the baby moved).
Contraction Stress Test (CST)
The CST is often done if the non-stress test is abnormal. The purpose is to predict how well the baby will do during labor (which is a stressful process not just for you, but the baby as well). Every contraction momentarily deprives the baby of its usual blood and oxygen supply. For most babies this is not a problem, but some babies have a hard time. A CST shows whether the baby has an abnormal heart rate pattern during contraction stress.
Again, a fetal monitor is used. To cause contractions, you may be asked to stimulate your breasts by placing a warm compress on one of them or by rubbing your nipples. If this does not cause adequate contractions, you will be given an injection of oxytocin (Pitocin), which is secreted naturally by every woman in normal labor. The resulting contractions are similar to those you will have during labor. If the baby's heart rate slows down rather than speeding up after a contraction, the baby may be having a problem and may have more serious problems during labor.
This test is not 100% accurate and may be repeated to ensure its accuracy. Most women describe the test as slightly uncomfortable but not painful.
If the test is abnormal, you may be admitted into the hospital. If there is a problem with the baby, your doctor may want to deliver the baby early, by cesarean section.
Biophysical Profile (BPP)
A biophysical profile is a combination of a non-stress test and detailed ultrasound scanning. If the non-stress test is abnormal, then a biophysical profile may be done. The profile looks at fetal movement, fetal body tone, fetal breathing efforts, amniotic fluid volume, as well as the result of the non-stress test.
Each component is given a score of "2" if the result is normal, and "0" if the test is abnormal. A score of 8-10 is normal. A score of 6 is unclear and you may be required to repeat the test within 12-24 hours. A score of 0-4 is abnormal and often means the baby might be better off receiving care outside the uterus, and a cesarean section may be recommended.
Modified Biophysical Profile
In some cases, a modified biophysical profile is done. This combines the non-stress test with an ultrasound that just looks at the amniotic fluid volume. If both of these tests are normal, some doctors believe that this is as reassuring as the full biophysical profile. Furthermore, it is less time consuming. Your doctor will recommend the tests that are best for you and your baby.
If you are having a healthy pregnancy, these tests may never be done. If you are at high-risk or have gone a week or so past your due date, your doctor may decide that some of these tests are needed.
Review Date: June 29, 2001
Reviewed By: Peter Chen, M.D., Obstetrics and Gynecology, University of
Pennsylvania School of Medicine. Review provided by VeriMed Healthcare
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