What is a Nonstress Test & Why Is It Done?

What Is A Nonstress Test?

A nonstress test is a type of prenatal test that is carried out to check the baby’s health. The nonstress test is used to monitor the baby’s heart rate and also see how the heart rate responds to the baby’s movements. (1)

The test is ‘nonstress’ because there is nothing done to place any type of stress on the baby while the test is being performed.

During pregnancy, you typically start to feel the fetus move as early as 16 weeks. As the pregnancy progresses further, you will find the baby becoming more and more active inside. (2) With the increasing movement of the baby, the fetal heartbeat will also increase. Having a healthy and robust heartbeat indicates that the baby is healthy, and getting sufficient oxygen in the womb.

However, there are some cases where the baby does not move too much, or the movements are slowed down. This might be an indication that the baby is not getting sufficient oxygen and is at a higher risk of developing complications. The goal of any pregnancy is to, of course, maintain the health of the mother and the baby. If the baby is not getting sufficient oxygen, then you may need to have an early delivery, leading to a premature baby.

A nonstress test is typically recommended when the baby is believed to be at an increased risk of death, or when the mother has a complication such as preeclampsia or gestational diabetes. It can also be performed if the mother needs to undergo a procedure like an amniocentesis. (3)

If the mother is at risk of any such pregnancy complications, the nonstress test is performed to check the health of the baby. In fact, women who are a high risk end up undergoing several nonstress tests during the course of their pregnancy. The test is administered as often as once or twice a week.

There is no need to be afraid of such frequent nonstress tests because this test does not pose any risk to either the baby or to the mother.

What Is The Need For A Nonstress Test?

Even though the nonstress test is a standard part of all prenatal screening programs, not every pregnant woman needs to undergo this test. Doctors usually advise for this test under certain circumstances.

Women who have a high-risk pregnancy usually need to undergo the nonstress test. This might be due to a medical condition that is putting stress on the baby or the baby’s heart. These conditions may include:

You will also need to have a nonstress test if you have developed high blood pressure or diabetes during the pregnancy. Gestational diabetes and high blood pressure (or preeclampsia) both put you and the baby at high risk, and many types of tests are carried out to ensure that the baby and mother are healthy. (4, 5)

Doctors also recommend the nonstress test when a once active baby begins to show signs of slowed down movements or stops moving altogether.

As you get closer to the end of pregnancy and your due date, the baby’s movements should significantly increase instead of slowing down. So when the movement slows down or stops completely, it is a matter of concern. (6) This is why if you notice any change in the baby’s pattern of movement, you must immediately inform your doctor.

However, it is also essential to keep in mind that a growing fetus does not have any specified number of movements that should be happening every day. Since every baby is different, so are the movement patterns of each child. Nevertheless, less movement and activity can sometimes indicate a complication or problem, which is why a nonstress test is done to rule out any concerns.

Your doctor may also recommend a nonstress test in the following conditions:

  • If you are expecting twins or other higher-order multiples (7)
  • If you have a history of pregnancy complications
  • You have low amniotic fluid (8)
  • Your doctor suspects some problem with fetal growth
  • You are two weeks above your due date

When Is A Nonstress Test Administered?

A nonstress test cannot be administered until the beginning of the third trimester of your pregnancy. This typically begins at around 32 weeks, but in some high-risk pregnancies, it might be earlier.

There is no need to make any special preparations for this test. The test takes place in your doctor’s office itself.

How Is A Nonstress Test Performed?

A nonstress test is a short test that only lasts for about 20 to 30 minutes. It is performed by a nurse, and your doctor or midwife is also present for interpreting the results. (9)

Your blood pressure will be checked before the test, and also at different times during the testing. You will be made to lie down on the examination table, and the nurse will apply a special gel to your abdomen.

A transducer will then be attached around your stomach. The transducer functions as an external fetal heart rate monitor for checking the baby’s heartbeat. In some cases, a uterine monitor will also be applied to check for any uterine contractions.

You will be asked to push a button every time you feel the baby move. You will be given a buzzer or clicker in your hand to click at every movement you feel. Each buzz or click will send the information about the movement to the computer monitor.

If the baby is awake and actively making movements at the start of the test, then the nonstress test tends to last only for 20 minutes. However, if the baby is asleep or inactive, then the test can take longer. In case the baby is asleep, the nurse first makes an effort to wake up the baby by placing a noise-making device over your abdomen.

Additionally, eating or drinking can also wake up the baby and make them active.

What Do The Results of Nonstress Test Indicate?

You don’t need to wait for a couple of days to get the results of this test. You will get to know the results of a nonstress test at that time itself before leaving the doctor’s office.

The results of a nonstress test are either nonreactive or reactive. A reactive report means that the baby’s heart rate and pattern of movement are both normal, and the baby is healthy. It also indicates that the baby is not under any type of stress, and the heart rate is normally increasing with movement as it should be.

Nonreactive test results indicate that the baby does not meet the minimum number of movements that the test specifies as normal for that fetal age. It may also mean that there was no change observed in the baby’s heart rate with the movement pattern.

There is no need to get afraid of a nonreactive result. This may also mean that the baby was still asleep, and it might have been uncooperative during the test. Maternal position may also play a role. (10) Some experts also believe that the gestational age of the fetus may also have a link with a nonreactive test result. (11) Doctors will repeat the test again if the first result is nonreactive.

What Happens After The Nonstress Test?

If the results of your nonstress test is nonreactive, then your doctor is going to recommend that you repeat the test again, perhaps with more extended monitoring.

Sometimes the test might be repeated on the same day, or your doctor may call you back again the next day. Your doctor may also prescribe certain other diagnostic tests, such as a biophysical profile. This test helps monitor the baby’s breathing, amniotic fluid level, and also the baby’s body movements.

Depending on the results of your second nonstress test and/or any other tests your doctor recommends, your doctor will then determine if your baby is really under stress.

At this point, your doctor will let you know whether there is a need to go in for further testing or whether, looking at the gestational age, the doctor will discuss about inducing labor.

If you are expecting more than one baby or if you have a high-risk pregnancy, you are likely to undergo multiple nonstress tests during your pregnancy, even if the previous test results have been reactive. This is one of the conventional methods of monitoring the baby’s health during high-risk pregnancies.

Conclusion

A nonstress test is a non-invasive test for your baby that helps ensure that the baby is in good health, and it is moving normally as per its gestational age. While the test is usually done on most pregnant women, it is especially important in women who have a high-risk pregnancy or who have had complications in their previous pregnancies.

The results of the test may cause you some concern, but instead of worrying, work with your doctor to find the best solution to keep you and your baby healthy.

References:

  1. Nochimson, D.J., Turbeville, J.S., Terry, J.E., Petrie, R.H. and Lundy, L.E., 1978. The nonstress test. Obstetrics and gynecology, 51(4), pp.419-421.
  2. Mangesi, L., Hofmeyr, G.J., Smith, V. and Smyth, R.M., 2015. Fetal movement counting for assessment of fetal wellbeing. Cochrane Database of Systematic Reviews, (10).
  3. Stanfordchildrens.org. (2020). default – Stanford Children’s Health. [online] Available at: https://www.stanfordchildrens.org/en/topic/default?id=amniocentesis-procedure-92-P07762 [Accessed 1 Mar. 2020].
  4. Karumanchi, S.A. and Granger, J.P., 2016. Preeclampsia and pregnancy-related hypertensive disorders. Hypertension, 67(2), pp.238-242.
  5. Bryson, C.L., Ioannou, G.N., Rulyak, S.J. and Critchlow, C., 2003. Association between gestational diabetes and pregnancy-induced hypertension. American journal of epidemiology, 158(12), pp.1148-1153.
  6. Pregnancybirthbaby.org.au. (2020). {{meta.og.title}}. [online] Available at: https://www.pregnancybirthbaby.org.au/baby-movements-during-pregnancy [Accessed 1 Mar. 2020].
  7. Urmc.rochester.edu. (2020). Complications of Multiple Pregnancy – Health Encyclopedia – University of Rochester Medical Center. [online] Available at: https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=85&ContentID=P08021 [Accessed 1 Mar. 2020].
  8. intermountainhealthcare.org. (2020). What Does Low Amniotic Fluid Really Mean. [online] Available at: https://intermountainhealthcare.org/blogs/topics/intermountain-moms/2018/05/what-does-having-low-amniotic-fluid-really-mean/ [Accessed 1 Mar. 2020].
  9. Brown, R. and Patrick, J., 1981. The nonstress test: how long is enough?. American Journal of Obstetrics and Gynecology, 141(5), pp.646-651.
  10. Abitbol, M.M., Monheit, A.G., Poje, J.O.A.N.N.E. and Baker, M.A., 1986. Nonstress test and maternal position. Obstetrics and gynecology, 68(3), pp.310-316.
  11. Druzin, M.L., Fox, A., Kogut, E. and Carlson, C., 1985. The relationship of the nonstress test to gestational age. American journal of obstetrics and gynecology, 153(4), pp.386-389.

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