A contraction stress test uses devices placed on your belly (an external fetal monitor) to record your baby’s heart rate after you are given medicine to cause contractions. The test records your baby’s heart rate and your contractions.
Most contractions decrease the flow of blood and oxygen to your baby for a short time. Normally, this does not change a healthy babyâ€™s heart rate. By seeing how your baby’s heart rate reacts to contractions, your healthcare provider can tell if your baby will be able to handle the stress of labor.
This test is also called an oxytocin challenge test.
When is it used?
One or more contraction stress tests may be done after 26 weeks of pregnancy. Your healthcare provider may recommend a contraction stress test if:
Your pregnancy is high risk because you are pregnant with more than 1 baby, you are older than 35, or you have high blood pressure.
Your baby’s heart rate did not change as expected in other tests.
Your baby does not seem to be growing normally.
You had problems in a previous pregnancy, such as a baby who died at birth.
How do I prepare for this test?
Your healthcare provider will tell you when to stop eating and drinking before the procedure. This helps to keep you from vomiting during the procedure.
You may or may not need to take your regular medicines the day of the procedure. Some medicines (like aspirin) may increase your risk of bleeding during or after the procedure. Tell your healthcare provider about all medicines and supplements that you take. Ask your provider if you need to avoid taking any medicine or supplements before the procedure.
Pregnant women should not smoke, but if do you smoke, do not smoke for at least 4 hours before the test. Smoking can decrease your babyâ€™s movements.
Tell your healthcare provider if you have any food or medicine allergies.
Follow any other instructions your healthcare provider gives you.
Ask any questions you have before the procedure. You should understand what your healthcare provider is going to do. You have the right to make decisions about your healthcare and to give permission for any tests or procedures.
What happens during the test?
You will need to have contractions strong enough to measure during the test. If you are not having contractions, or they are not strong enough, you will be given medicine called oxytocin. The oxytocin may be given until you have 3 contractions, each lasting 40 seconds, in 10 minutes.
You will lie on your left side during the test. The instruments used for are attached to your belly with 2 elastic belts. One belt has a small ultrasound device to record your baby’s heart rate. The other belt has a gauge to record your contractions during labor. The results are viewed as graphs on a TV screen.
If your babyâ€™s heart rate is not normal your healthcare provider may admit you to the hospital for monitoring.
What are the risks of this test?
Every procedure or treatment has risks. A possible risk of this procedure is:
The stress test could cause too many contractions and you may go into labor.
Ask your healthcare provider how the risks apply to you. Be sure to discuss any other questions or concerns that you may have.
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Adult Advisor 2015.1 published by RelayHealth. Last modified: 2014-09-22 Last reviewed: 2014-09-22
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Contraction Stress Test: References
ACOG Practice Bulletin: Management of Intrapartum Fetal Heart Rate Tracings. Number 116, November 2010.
Cunningham, F. et al. Williams Obstetrics. 22nd ed. The Mcgraw Hill Companies, Inc. 2008. Accessed February 1, 2009 from http://www.accessmedicine.com.
Gibbs, R., et al. Danforthâ€™s Obstetrics and Gynecology. 9th ed. Lippincott Williams and Wilkins, 2008. Accessed on February 1, 2009 from http://www.ovidsp.tx.ovid.com.
Lockwood, C. Guidelines for Perinatal Care. 7th ed. AAP and ACOG. October 2012.