What Is A Contraction Stress Test During Pregnancy & Why It Is Done?

Contraction Stress Test

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Are you pregnant and going through a litany of tests that your doctor has recommended? Do you worry that you are never sure about what the tests are for and whether or not they can lead to any side effects in your unborn baby? Would you like to know more about some of the tests that your doctor has recommended in the near future? Has your doctor asked you to do something known as a contraction stress test and you have no idea what it is?

If you are looking for more information about a contraction stress test during pregnancy, scroll down and read all about it here.

What Is A Contraction Stress Test?

A contraction stress test or the stress test or the Oxytocin challenge test usually occurs while you are pregnant. The doctor asks you to take the test to measure your baby’s heart rate while you have uterine contractions. The test helps your doctor and his medical team check your unborn baby’s response and health when you experience a decrease in your oxygen levels at the time of your labor contractions. In most cases, your doctor will ask you to take the test when you are at least 34 weeks into your pregnancy or more. It includes external fetal heart rate monitoring as well.

When you have a uterine contraction, your body will experience a decrease of blood and oxygen that your unborn baby receives. In most cases, it does not cause any problems in your baby. Sometimes, though, it can cause a decrease in the heart rate of some babies. To measure the change, your doctor and medical team will monitor your unborn baby’s heart rate using the external fetal monitoring device.

[ Read: Types Of Contractions During Pregnancy ]

Why Is The Contraction Stress Test Done?

It is possible that your doctor asks you to go for more than one contraction stress test while you are pregnant. Your doctor may ask you to go for a contraction stress test to check for the following situations:

  • To see if your unborn baby will be able to stay healthy when there is a drop in the oxygen levels at the time of contractions that you will experience during labor.
  • To see if your placenta is healthy and whether or not it will be able to support your baby properly.

In some cases, if you have already undergone a non-stress test or a biophysical profile, your doctor may ask you to go for a contraction stress test procedure. In a biophysical profile test, the doctor or technician will use an ultrasound during a non-stress test. It will help measure the various physical characteristics of your baby.

The reason for this will most likely be the fact that your results from the other two tests were not conclusive enough, and the contraction stress test will help your doctor get a clearer picture.

[ Read: Essential Tests To Take During Pregnancy ]

How Should You Get Prepared For The Contraction Stress Test?

Once your doctor tells you that you have to go for the contraction stress test, here are a few ways you can get yourself ready for the same:

  • Check with your doctor or medical team whether you have to stop eating for a few hours before the test. Usually, you will have to eat or drink anything for about four to eight hours before your test happens. You may also be asked to empty your bladder before you can begin the test.
  • The medical team will ask you to sign a consent form that will say that you understand any risks that are associated with the test, and you do agree to go ahead with it.

If you are worried about the test and what it entails, make sure to speak to your doctor before you go for the same.

How Is The Contraction Stress Test Done?

A contraction stress test will usually be done in your doctor’s office or in the hospital that you visit. Sometimes, it can also be done by an obstetrician or a trained laboratory technician or even a trained nurse. In most cases and unless absolutely required, you do not have to stay at the facility for the night. Depending on how you and your unborn baby react to the test, the contraction stress test can take about two hours to complete.

Here is a look at what happens during a contraction stress test:

  • You will first have to lie down comfortably on a bed and slightly raise your back. Your doctor, nurse or the staff will gently help you tilt a little towards your left side. It will help avoid any pressure on the blood vessels that lie on your belly.
  • Once you are comfortable, the staff or doctor will place two belts around your belly. The belts will be fitted with sensors that will help the doctors to check the reading. One belt will have a sensor to record the heart rate of your baby while the sensor in the other belt will help to measure your uterine contractions.
  • The doctor may choose to use gel on your skin while using the sensor that monitors your baby’s heart rate.
  • Once you are set, the staff will hook the sensors to a recording device. If your baby changes his position, the doctors may change the position of the heart rate monitor as well.
  • The doctor and team will record your baby’s heart rate and your contractions for at least ten minutes. During this time, other important data like your blood pressure and your vital signs will also be recorded.
  • Your doctor will administer you a dose of the hormone oxytocin. Initially, your doctor will give you a low dose, but will gradually increase the dosage till you get at least three contractions within a span of ten minutes.
  • As your contractions progress, each contraction will last longer by the previous one by 45 seconds.
  • In case the contractions do not take place, your doctor will ask you to massage only one nipple by using your hand. If you still do not have a contraction within the next two minutes of your first contraction, your doctor will ask you to massage your nipple again. In case you do not get a contraction even in the next 15 minutes, your doctor will ask you to massage both your nipples.
  • Once your test is over, and the doctor is happy with the way it has progressed, the medical team will keep you under watch until the time your contractions slow down or go away completely. Your contractions will have to get down to what they were before you began the test before you can leave (1).

Does The Contraction Stress Test Feel Uncomfortable Or Painful?

The contraction stress test helps your doctor and medical team assess the risk factor for your unborn baby when you experience your labor contractions. Even though it may feel uncomfortable for some time, the discomfort will soon be over.

Here are a few situations that may make you feel uncomfortable during the test:

  • During the test, you will need to lie down on your left side. Sometimes, the position could be a little difficult or uncomfortable for you, especially during your last trimester or final weeks of the pregnancy. Lying down on your left side can also feel uncomfortable if you start having your labor contractions.
  • Sometimes, having the belts around your stomach can also be quite uncomfortable. The belts have sensors that will help monitor your baby’s response to your labor contractions. While most women do feel that the belt and the sensor devices feel uncomfortable, there are usually no complaints about any pain or other side effects.

Are There Any Risks Of The Contraction Stress Test During Pregnancy?

While most doctors feel the contraction stress test is safe during pregnancy, there can be certain risks or side effects. Here is a look at some side effects of the test that you can keep in mind:

  • During the contraction stress test, the doctors will check for the fetal heart rate monitoring. In some cases, the fetal heart monitoring tends to indicate that your unborn baby is having some difficulty. However, in reality, it could be possible that your unborn baby is fine and is not going through any discomfort. It is one drawback of the fetal heart rate monitoring process that is done as part of the contraction stress test during pregnancy.
  • Another drawback of the fetal heart monitoring process is that it is not able to pick up any issues, such as birth defects, that your unborn baby may have. It means that while it can only check the heart rate of your unborn baby, it does nothing to detect any other health or related issues your unborn baby could be going through.
  • While you go through the contraction stress test during your pregnancy, you are given a shot of oxytocin to help you get into the labor contractions that are required as part of the test. In some cases, it can be a cause of concern because it can initiate your labor to start earlier than your due date.
  • The oxytocin that you administer during the contraction stress test helps start the labor contractions that will help your doctor and medical team check your unborn baby’s response. Sometimes, the oxytocin can prolong the contractions that you have during the test, and cause difficulties for your unborn baby. In some cases, it can also lead to problems for your unborn baby. In most cases, the labor contractions stop when the oxytocin shots stop. Sometimes, if your labor contractions go on longer than it was intended to, your doctor may give you some counter medication that will help to stop the contraction. In a rare case, if nothing helps and the labor contractions that you experience do not stop, your doctor may have to go in for an emergency delivery to help take your baby out (2).

[ Read: What Is The Rh Factor Test ]

Are There Any Instances When The Contraction Stress Test Is Not Recommended?

As a pregnancy stress test can sometimes lead to prolonged contractions that may require immediate birth, your doctor may instead ask you to go for the biophysical profile.

  • A biophysical test will check your baby’s health while still inside the womb. It is mostly done by using electronic fetal heart monitoring and a fetal ultrasound. The biophysical test, or BPP, will measure your unborn baby’s heart rate, your baby’s muscle tone, breathing, movement as well as the amount of amniotic fluid that is present in your baby.
  • A biophysical test will most likely occur during the last trimester of your pregnancy. In case your doctor confirms that you have a high risk pregnancy, where your baby can have some complications during pregnancy, the BPP test will occur by the 32nd or the 34th week. In some cases, it may happen earlier. If you are at an extremely high risk case of a high-risk pregnancy, your doctor may ask you to get a BPP test done at least once every week and at least twice every week during the third trimester.

The BPP test is carried out with the help of a non-stress test as well as with the help of fetal ultrasound. Here is how both the tests are carried out as part of the BPP test:

[ Read: Is Ultrasound Safe During Pregnancy ]

1. The Non-Stress Test:

In the non-stress test, a fetal heart monitoring system will record your unborn baby’s data while your baby is moving in the womb, and while your baby is not moving.

  • A non-stress test will most likely occur just before you go in for a fetal ultrasound.
  • For the external monitoring, two sensors will be attached to elastic belts that will be placed around your stomach.
  • One sensor will use reflected sound waves to check your baby’s heart rate. The other sensor will measure how long your contractions lasted.
  • Sometimes, your baby’s heartbeat will sound like a beep while at other times it could simply be noted as a graph on a printed page.

[ Read: Non Stress Test During Pregnancy ]

2. The Fetal Ultrasound:

For a fetal ultrasound, you will have to perform the prenatal stress test while your bladder is full.

  • You will have to lie down on your back, and the technician will put some gel on your stomach. Your doctor will use a small device called the transducer to move across your stomach and watch your baby on the screen.

How To Read The Results Of A Contraction Stress Test During Pregnancy?

The main aim of a contraction stress test is to see the way your unborn baby will react at the time when your real labor contractions start. The test will help your doctor and your medical team to check whether or not your baby will be alright when there is a drop in the oxygen and blood flow at the time of labor contractions.

The contraction stress test results will only give your doctors the result of your baby’s health for about a week. Your doctor may want to perform the test again and even multiple times during the pregnancy.

Here is how you can read the results of the contraction stress test during your pregnancy, both in case of a normal or an abnormal reading:

1. Normal Test Result:

When a contraction stress test result comes out as normal, it is known as a negative contraction stress test result.

  • In this part of the result, it is seen that your baby’s heart rate will not become slower or decelerate, nor will it stay slow after the contractions are over.
  • During the tests, there may be a few times when your baby does show a decline in the heart rate. It will soon get back to its normal rhythm and will not cause any problem.

2. Abnormal Test Result:

When a contraction stress test result comes out as abnormal, it is known as a positive contraction stress test result.

  • In this part of the result, it is seen that your baby’s heart rate will become slower or decelerate, and it will stay slow after the contractions are over. The same will be true for more than half of the labor contractions that you will experience during the test.
  • During the tests, when your baby goes through a late deceleration, it means that your baby will also have difficulty and will face problems at the time of the normal labor (3).

[ Read: Genetic Testing During Pregnancy ]

Can Something Affect The Results Of The Contraction Stress Test?

While it is not always the case, there may be situations that could prevent you from having the test, or where the results of the test may not be of any help. Here are a few situations you can expect:

  • If you have had problems in your earlier pregnancy, it could affect your test result. Some problems in an earlier pregnancy that affect the test result include a cesarean section birth with a midline (vertical) incision, a placenta abruptio or a placenta previa.
  • In case you are carrying twins or multiple babies in this pregnancy, doctors will not recommend the contraction stress test. It could have a negative impact on your unborn babies and make the results inconclusive.
  • Your doctor will ask you to avoid the contraction stress test if you have been administered magnesium sulfate while you were pregnant, or if your doctor feels that you have an incompetent cervix.
  • If you have had a uterine surgery in the past, there is a risk that the contraction stress test could cause a uterine rupture. Your doctor will not recommend a contraction stress test in this case.
  • If you have smoked during your pregnancy, your doctor will recommend you to stay off the contraction stress test.
  • If your baby moves too much during the contraction stress test, it will be difficult for the sensors in the belt to record your baby’s correct heart rate as well as the information related to contractions. In such a case, even though you may be doing the test until the end, the results can come out incorrect or inconclusive.
  • If you are overweight, it could have an incorrect reading in your contraction stress test results.

[ Read: Cardiotocography During Pregnancy ]

A Few To Keep In Mind About The Contraction Stress Test:

Going through a contraction stress test can be an important thing while you are pregnant, especially as it will tell you how your unborn baby will cope when you have those real labor contractions. While you may be tense during the test and worry more after the results are out, it is important to remember a few things about the test. Here are a few points you should keep in mind about the test and its result:

  • A contraction stress test can sometimes give the result of a deceleration in your unborn baby’s heart rate, even when your baby is comfortable and not in any distress. When this happens, it is known as a false positive result.
  • In some cases, the doctors will only recommend you to be given oxytocin instead of going for the nipple stimulation process. It is done as a precautionary measure, as sometimes, stimulating your nipples could lead to longer contractions that can soon become uncontrolled and cause harm to your unborn baby.

Make sure to check with your doctor about any queries or concerns you have before you go for the tests. The tests are not a hard and fast rule as every pregnancy is different. However, if your doctor recommends you for a contraction stress test or oxytocin challenge test during gestation, you should go for one.

Did you have a contraction stress test during pregnancy? How was the experience? Tell us below.

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