If you are a mother-to-be, you must be constantly worrying about your baby's health, right? It's normal to wonder if your baby is doing well in the womb, is he struggling, or is there something wrong with him. So, sometimes doctors may order a special test to find out exactly how your baby is doing. One such important test is the `Contraction Stress Test (CST). Let's talk about this in detail and very simply today, shall we?
What is this `Contraction Stress Test (CST)`?
Simply put, a Contraction Stress Test (CST) is a test that measures how well your baby can withstand the pressure of uterine contractions (the tightening of the uterus as you prepare to deliver your baby). During this test, your doctor will give you a hormone (usually called oxytocin) that causes your uterus to contract . The contractions are similar to those you experience during labor, but they usually don't start labor.
Now imagine, when the uterus contracts to deliver the baby, the amount of blood and oxygen that the baby receives is temporarily reduced . Most babies have no problem tolerating this temporary decrease. They are well adapted to it. However, some babies' heart rates may remain low even after the contractions have ended. That's what the CST is used to see if something like that happens. To be precise, this test is done to get a little idea in advance of how the baby will react to the actual contractions when the baby is born.
Who wants to do this `CST`?
This `CST` is not usually done for everyone. A doctor will only recommend this `CST` if the results of a `Nonstress Test (NST)` or `Biophysical Profile (BPP)` that you have previously had are somewhat abnormal.
- Nonstress Test (NST): This checks your baby's heart rate and oxygen supply. This NST is usually done after 28 weeks of pregnancy.
- `Biophysical Profile (BPP):` In this, an `NST` is done along with an `(ultrasound)` test of the baby. This allows us to see things like the baby's heart rate, breathing, muscles, and movements.
So, if these tests raise any doubts about the baby, the CST is useful for further investigation.
What is the difference between a `Nonstress Test` and a `Contraction Stress Test`?
There is a slight difference in the name of both of these.
In a `Nonstress Test (NST),` the doctor monitors your baby's heart rate without applying any external pressure to the baby . They simply monitor the heart rate as the baby lies still.
However, in the `Contraction Stress Test (CST), we look at how the baby's heart rate changes under the "stress" that occurs when the uterus contracts. That is, we artificially create a small amount of pressure and see how the baby copes with it.
When is a CST performed during pregnancy?
Usually, a doctor will decide to perform this `CST` when you are 34 weeks or more pregnant, because by then the baby is mostly fully developed.
How does this `Contraction Stress Test` work? It's very simple!
During a Contraction Stress Test, your doctor or medical team will give you a small amount of a hormone called Oxytocin. Oxytocin is a hormone that naturally helps the uterus contract during labor.
So, when you give this hormone, your uterus starts to contract. Then, the medical team carefully monitors your baby's heart rate during contractions and during the breaks between contractions. If the baby's heart rate remains low after a contraction , it means that the baby may have difficulty coping with the contractions that occur during actual labor.
How should I prepare for `CST`?
You will receive some special instructions from your doctor before a `CST`. It is very important to follow those instructions exactly.
- Typically, you will be asked not to eat or drink anything for four to eight hours before the test.
- If you are a smoker, your doctor will tell you to stop smoking at least two hours before the test. Smoking can slow down the baby's heart rate, which can affect the test results.
What should we expect when doing the `CST`? Can you explain a little bit?
A `Contraction Stress Test` is usually an outpatient test . This means you can go home the same day. Here's what happens during the test:
- You will be made to lie down on a bed, with your back slightly elevated.
- A nurse will come and tie two straps with sensors around your belly. One sensor measures the baby's heart rate. The other records your uterine contractions.
- The hormone ``(Oxytocin)'' is given to you through an ``(IV line)'', like saline given into a vein.
- Sometimes, your doctor may recommend massaging your nipples to help start uterine contractions, as this will naturally increase the production of oxytocin.
- The medical team will carefully record your baby's heart rate as contractions occur.
- When the test is finished, the nurse removes the IV. The contractions gradually decrease and stop.
After the test, the medical team will monitor you until your contractions have completely stopped . Sometimes, if the contractions don't stop, your doctor may give you medicine to stop them. The entire test can take about two hours .
Are there any risks with this `Contraction Stress Test`?
The `Contraction Stress Test` is generally a very safe test . There is nothing to be afraid of.
However, the biggest risk is that this test could cause you to go into premature labor . This means that you may experience labor pains before the baby is due. This is also very rare.
Are there people who don't want to do a `CST`?
Yes, this `CST` is not suitable for some people. For example:
- If you are expecting twins, triplets or more , it may not be appropriate to have a CST, as this test is more likely to induce labor at that time.
Therefore, it is your doctor who will decide whether this test is suitable for you or not.
What do the results of the `CST` say? Let's understand.
The results of the `CST` mainly tell you how your baby's heart rate responds to uterine contractions, that is, whether or not the heart rate slows down after the contractions.
- If the result is Normal / Negative: This is the best result! It means that your baby's heart rate has not slowed down after a contraction. It means that the baby is coping well with the pressure in the uterus. Doctors sometimes say that this is called ``late decelerations''.
- If the result is Abnormal / Positive: This means that your baby's heart rate has slowed down after the contractions have finished and remains at that low level for a while. This means that the baby may be having difficulty coping with the pressure of the contractions during labor.
What happens if the `CST` result is `Positive` (abnormal)?
If your CST test result is ``Positive`` (meaning abnormal), it means that your baby may not be able to withstand the stress of the contractions during labor. If so, your doctor may recommend some more tests. You may also be asked to do another CST in a week or two.
If the results continue to be ``positive,'' meaning that the baby is more likely to have complications during delivery, your doctor may recommend a cesarean section (C-section) for your and your baby's safety. All of these decisions are made to ensure the maximum safety and well-being of you and your baby.
How many times can a `CST` be done?
A CST measures how healthy your baby is at the time of the test . Therefore, you may have to have several CST tests during the last few weeks of your pregnancy.
In particular, if the results of a previous CST suggest that your baby may have difficulty coping with labor contractions, your doctor may recommend a weekly CST . This is to continue to closely monitor your baby's condition.
Things to remember in summary
Okay, so let's recap the most important points from what we've talked about.
A `Contraction Stress Test (CST)` is a test that measures your baby's heart rate during uterine contractions. During these contractions, the amount of oxygen and blood the baby receives is temporarily reduced. Most babies can tolerate this.
Most importantly, if the baby's heart rate remains low even after the contractions have ended, it means that the baby may be having difficulty coping with the pressure of the contractions during labor.
If your CST result is `Positive` (abnormal), don't panic. Your doctor will talk to you about any additional tests you may need, and if necessary, a cesarean section. Remember, this is all for your and your baby's safety. Talk to your doctor about this and ask any questions you may have. That's the best thing to do!
` Contraction Stress Test, pregnancy, baby's health, labor, oxytocin, heart rate, uterine contractions
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