Table of contents:
- Definition
- What is a contraction stress test?
- When should I have a contraction stress test?
- Precautions & warnings
- What should I know before undergoing a contraction stress test?
- Process
- What should I do before undergoing a contraction stress test?
- How is the contraction stress test process?
- What should I do after undergoing a contraction stress test?
- Explanation of the Test Results
- What do my test results mean?
- What affects the test results?
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Definition
What is a contraction stress test?
The contraction stress test serves to check whether the condition of the baby (fetus) remains healthy during the reduction of oxygen which usually occurs when contractions occur while you are working. This test monitors the fetal heart rate. This test is done when the gestational age is at week 34 or more.
During uterine contractions, a supply of blood and oxygen is provided to your baby for a short time. This is not a problem for most babies. However, some babies may have a decreased heart rate. This change in heart rate can be seen on an external fetal monitoring device.
During the contraction stress test, the hormone oxytocin is injected into you through a vein (intravenously, or IV) to trigger labor contractions. You may also be asked to massage your nipple area to release oxytocin. If your baby's heart rate decreases (decelerates) in a certain pattern instead of increasing (accelerating) after contractions, your baby may have problems with normal delivery.
A contraction stress test is usually done if you have an abnormal nonstress test or a biophysical profile. A biophysical profile using ultrasound during a nonstress test is performed to determine the characteristics of your baby. There may be more than one contraction when the test is performed.
When should I have a contraction stress test?
A contraction stress test is performed to check:
- whether your baby remains healthy during the reduction in oxygen that occurs while you are working
- whether the placenta is healthy and has a good effect on your baby
A contraction stress test may also be performed if the results of the nonstress test or the biophysical profile are abnormal.
Precautions & warnings
What should I know before undergoing a contraction stress test?
The contraction stress test may show a decrease when your baby has no problems. This result is called false-positive result (false positive result). For some reason, contraction stress tests are rarely used nowadays. In most cases, practitioners can review the baby more quickly and safely by performing a biophysical profile test while on a nonstress test, or both. Some doctors may perform a biophysical profile or double ultrasound test instead of a contraction stress test.
Process
What should I do before undergoing a contraction stress test?
You may be asked not to eat or drink anything for 4 to 8 hours before the test. Empty your bladder before the test. If you smoke, you should stop smoking 2 hours before the test, because smoking can cause activity and the baby's heart rate to decrease. You are asked to sign a file stating that you understand the risks that can occur and agree to the conditions.
Talk with your doctor about all things related to the test, such as the risks, how the test is performed, and the results of the test.
How is the contraction stress test process?
You will be asked not to eat or drink anything 6 to 8 hours before the test, as sometimes this test can lead to an emergency caesarean section (it's best to empty your bladder and urinate before the test). When the test is done, you are asked to lie on your left side. A technician will place two devices around your stomach: one to monitor the baby's heart rate; and another to record uterine contractions. The machine records the baby's contractions and heart rate on two different charts. The test is done until there are three contractions in 10 minutes, usually lasting 40 to 60 seconds. This test can last for 2 hours. You may not feel any contractions or you may just feel cramped like a period, not going to induce labor.
If no contractions occur during the first 15 minutes, the practitioner may try to give a small dose of synthetic oxytocin (pitocin) by IV to stimulate the nipple, releasing natural oxytocin.
What should I do after undergoing a contraction stress test?
After the test, you will usually be monitored until there are no more contractions or the contractions have decreased as they were before the test. This contraction stress test may last for 2 hours.
Explanation of the Test Results
What do my test results mean?
The test results describe your baby's health condition during the week. This test may have to be done more than once during pregnancy.
| Contraction stress test | |
| Normal: | A normal test result is called negative
Your baby's heart rate stays and gets weaker after the contractions. Note: There is a chance that your baby will experience decelerates (weakened heart rate), but this condition will not last long, so it is not a serious problem. If there are contractions for 10 minutes from stimulation of your nipples or oxytocin infusion and the deceleration does not appear late, it is hoped that the baby's heart rate can be controlled. |
| Abnormal | Abnormal test results are called positive.
The baby's heart rate gets weaker (decelerates) and remains weak after contractions occur. This occurs in the middle of the contraction. The slow contractions may mean that there is a problem with your baby. |
What affects the test results?
Some reasons why you may not be able to do this test, or the test results may not be accurate, include:
- problems in previous pregnancies, eg vertical incisions. This test also should not be done if you are carrying twins or more, or if you were prescribed sulfates during pregnancy
- ever had uterine surgery. The strong contractions can cause the uterus to tear
- if you smoke
- movements in the baby during the test because it is very difficult to record the baby's heart rate and contractions
