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Ask A Childbirth Educator
Questions and Answer

Q. What is a stress test and what does it involve?

A. A stress test, or OCT (oxytocin challenge test), is a prenatal test done to check fetal well-being during a simulated "labor". It is largely been replaced with the non-stress test, or NST, nowadays. The OCT is usually performed during the last weeks of pregnancy. The mother goes in and is hooked up to the fetal monitor. An IV line is run, and she is given a small amount of pitocin until she has at least three contractions withint ten minutes. The monitor strip is assessed to decide how the baby might possibly handle labor. (Babies who show an abnormal heart rate during contractions are considered to be "stressed" and possibly should not go through labor.) Obviously there are some drawbacks to this test....one is that a woman may end up with an induction of labor by accident fromt he pitocin. Another is that there is a very high rate of false positives (25%), often due to the position of the mother during the test. She is often laying down flat on her back, where the uterus is compressing the major blood vessels, reducing blood flow to the baby which changes its heart rate. Also if the test is done too soon, (remember due dates can be off by two-three weeks) a premature baby going through the test will mostly likely "fail", so will be delivered by induction with the practitioner thinking the baby won't handle labor as it is "postmature", only to deliver a premature baby who wasn't YET ready to go through labor. These are certainly not-insignificant drawbacks.

That is why the OCT has been replaced with the NST (Non-stress test). The non- stress test, while similiar, is less interventive. Again the mother is hooked up to an electronic fetal monitor to record the fetal heart rate. She records any movements of the baby and it is compared to the fetal heart rate tracing. The theory is that if the baby's heart accelerates, or increases, during a contraction, then it is a healthy baby. Results are recorded as positive (meaning a reactive baby who is healthy) or negative (which often will lead to more testing). Some factors that will skew the results of this test is that the baby may be asleep (making the heart rate slower) or maternal low blood sugar. Often caregivers will then have the mother drink orange juice or make some loud noises near her belly to "wake the baby up," and then continue the test. The main risk with the NST is based on getting a false negative result and intervening where there is no need. There are other factors to take into consideration when determining fetal well-being besides the NST results, including amount of fluid, fetal breathing movements, how the placenta is working etc. As this test is most often performed when a woman is past her due date, it is important to remember that in the literature, the high majority of babies even up to 2 weeks past their due date are still perfectly fine. Well- nourished mothers tend to grow healthy placentas that can adequately nourish the baby past the due date with no ill-effects.

Karen Klimsak-Ungar, CCE has been a certified childbirth educator for Birth Works® since 1996. She is currently Managing Editor for the Birth Works newsletter, sits on the Birth Works Board of Directors, and serves on their National Trainee Review Committee. A happily married mother of two, she also continues to teach Birth Works classes as well as private classes.

Karen will answer your questions on fertility, pregnancy, birth, breastfeeding and babies. Her advice does not take the place of your practitioner. Personal answers will not always be possible.