If your ob gyn recommends you have a non stress test during pregnancy, you might find your stress levels rising.
But rest assured, a nonstress test (NST) won’t stress out your baby.
An NST is a very common, non invasive prenatal method of reassuring you all is well with you and your baby.
A big bonus is you get to hear the reassuring sound of your baby’s heartbeat while recording all the kicks, rolls and punches!
Let’s take a look at these 11 facts about nonstress tests during pregnancy.
#1:What is a nonstress test during pregnancy?
The nonstress test checks on the well being of your baby during pregnancy. The nonstress part means that nothing is actually done to place stress on your baby during the test.
The test checks your baby’s heart rate and monitors your baby’s movements. It also monitors any contractions you might have and how your baby reacts to them.
You might also hear it referred to as a stress test or a contraction stress test. It’s also sometimes called a cardiotocography (CTG) which refers to the monitor used, which is called a cardiotocogram.
#2: How is a nonstress test done?
Having an NST is easily done at your doctor’s rooms or in the hospital antenatal clinic. You will be asked to lie on your left side on a bed or reclining chair. You will usually have your blood pressure checked before and after the procedure.
Two transducers are positioned over your belly and secured with elasticated belts:
- The doppler transducer is positioned to monitor your baby’s heart rate. This will be recorded on a graph
- The pressure transducer is positioned near the top of your bump to monitor any uterine contractions; this is why it’s called a contraction stress test by some health professionals.
You will be given a hand held button to press each time your baby moves and the movements will be recorded on the graph.
#3: How long does a nonstress test take during pregnancy?
The NST will normally take about 20 minutes. If your baby is asleep or isn’t very active, then it can take a little longer. You might have a break and then try again.
#4: What do they look for during NST?
The testing looks at the following things to give either a reactive or non reactive result:
- Your baby’s heart rate; the baseline or resting rate is between 110 and 160 beats per minute
- The presence of, or lack of variability in, the baseline heart rate
- Accelerations or short-term rises in your baby’s heart rate of at least 15 beats per minute, lasting at least 15 seconds. This means your baby’s heart beats faster than normally, for short periods
- Decelerations – temporary drops in the fetal heart rate. Normal nonstress test results show no significant decelerations below the established baseline or resting rate.
#5: Nonstress test pregnancy results
Once your test is complete, your care provider will look at all the information and give either a reactive or nonreactive result.
If your baby’s movement was normal for him, and he had a normal heart rate, he’s classed as healthy and not under any stress.
According to the American College of Obstetrics and Gynecologist, a normal or reactive stress test has:
- Two or more accelerations peaking at 15 bpm or more above baseline
- Each lasting 15 seconds or more
- All occurring within 20 minutes of beginning the test.
If your baby didn’t make the minimum number of expected movements during the timeframe of the test, or his heart didn’t accelerate as much as expected when moving, then the result is non reactive.
This result means your doctor might want to try it for longer.
#6: Can you fail a nonstress test?
It’s important to remember a non reactive result isn’t always ominous and could just mean your baby is sleeping.
The nurse might give you a sweet drink or snack to wake your baby up, and continue to monitor for a further 20 minutes.
Remember, the test is meant to offer reassurance about your baby’s health. It can sometimes cause anxiety for parents too.
It’s not unusual for a NST to suggest there’s a problem when in fact there’s none; this can lead to further testing to rule out risk factors.
Another test you might have is a biophysical profile, which combines the NST and ultrasound.
#7: Is a nonstress test painful?
The NST tests are completely painless and most mothers love to be able to hear their baby’s heartbeat on the monitors and see the movement reflected on the device.
#8: Should I eat before a NST?
It’s always advisable to have a snack or a meal before the test. I’m sure you have noticed how active your baby gets after meals?
If you haven’t eaten, the test might show up as non reactive. Your care provider might suggest a snack or sugary drink to wake the baby and continue the test for a further 20 minutes until it becomes reactive.
#9: How early can you do a nonstress test?
The NST tests are usually done only in the third trimester, from 32 weeks of pregnancy.
They aren’t usually done before 28 weeks gestation, as the baby isn’t developed enough to respond to the testing. This means results could be non reactive even though there’s no reason for that result.
Between 24 and 28 weeks, up to 50% of NSTs will be non reactive. Between 28 and 32 weeks, 15% of NSTs are non reactive.
#10: Does a nonstress test show contractions?
If you aren’t in labor when doing the test, the pressure transducer will be attached and will detect any mild contractions.
If you’re in labor, the pressure transducer is more important, as it shows how your baby responds to contractions.
During a contraction, the blood supply and oxygen supply to your baby changes as the muscles of your uterus tighten. The nonstress test can indicate to your health care provider whether your baby is getting enough oxygen.
#11: How often should a nonstress test be performed?
The frequency depends on why you’re having the test done and what your risk factors are for certain complications.
Here are some reasons why you might have a nonstress test, with suggested articles for further information:
- Suspected growth restriction (Does A Mother’s Diet Affect Baby’s Growth – 6 Things You Need To Know)
- Gestational diabetes (Gestational Diabetes – Diet and Symptoms)
- High blood pressure (Preeclampsia – Symptoms, Signs and Causes)
- Not feeling your baby move (Baby Kicking – 9 Important Facts You Need To Know)
- Past your due date (When Am I Overdue – What Pregnant Women Need to Know)
- Multiple/twin pregnancy (Pregnant With Twins – 8 Interesting Facts About Twins)
- Before labor induction (Natural Labor vs Induced Labor – 6 Main Differences)
- High risk pregnancy (What Is A High Risk Pregnancy And How Can I Best Avoid One?)
- Oligohydramnios (Low Amniotic Fluid Oligohydramnios).
In a healthy, low risk pregnancy your ob gyn might recommend a nonstress test between weeks 38 and 42. Some women don’t have any NSTs if there’s no medical indication to do one before labor started.
Your midwife might do one in early labor, to check on your contractions and monitor your baby’s heartbeat.
If you have a high risk pregnancy, your health care provider might recommend weekly nonstress testing after 28 weeks.
If you’re admitted to the hospital for observation during pregnancy, you might have a daily nonstress test for the duration of your stay.