Do Fetal Surveillance Tests Accurately Identify Babies at Risk?

by | Sep 1, 2026 | Pregnancy


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As you approach the end of pregnancy, it isn’t uncommon for your care providers to perform testing routinely to assess your baby’s well-being. The thinking behind this is that even in uncomplicated pregnancies, the baby may not be doing well. Tests can provide early warning of this, allowing delivery—usually by inducing labor—of a baby who appears to be at risk.

In this article, we’ll look at whether the evidence supports that rationale. We’ll look at four commonly used tests, what they measure, why they measure it, what the research concludes about whether they reduce newborn adverse outcomes, and whether there’s a downside to doing them. After that, as usual, I’ll wrap up with “Your Takeaway,” tips for making decisions and taking action based on what you’ve learned.

Fetal Surveillance Tests

The Nonstress Test, a.k.a. Antenatal Cardiotocography

A nonstress test involves monitoring the baby’s heart rate in response to pre-labor (Braxton-Hicks contractions) or the baby moving. A belt with two sensors is put around the belly. One is an ultrasound device like the one used during office visits to listen to the baby’s heart; the other is a pressure sensor that registers when the uterus tightens, or the baby moves. A baby whose heart rate doesn’t speed up may be in difficulty.

A systematic review (a study of studies on a topic) concluded:

We found no good evidence to support the use of traditional cardiotocography (CTG) or computerized CTG in pregnancy for improving fetal outcomes.8

Amniotic Fluid Volume Estimation

The amount of amniotic fluid is calculated during a sonogram. Reduced amniotic fluid volume (oligohydramnios) suggests there may be a problem.

A systematic review concluded:

To improve the accuracy of predicting future outcome risk for individuals, oligohydramnios … need[s] to be combined with other prognostic factors … It would seem prudent to limit its use to high-risk pregnancies.20

And a study added:

Active induction of labor in term low risk gestations with isolated oligohydramnios translated into higher labor induction, operative vaginal delivery and cesarean section rates. This led to increased maternal risk … with no differences in neonatal outcome.19

The Biophysical Profile

The biophysical profile combines a nonstress test, real-time ultrasonography to observe fetal breathing efforts and movements, and an amniotic fluid volume estimation.1 The thought is that combining tests will reduce results suggesting a problem when the baby is fine (false positives). A review concluded:

There is insufficient evidence … to support the biophysical profile (BPP) as a test of fetal wellbeing in high-risk pregnancies. … Combined data from the two high-quality trials suggest an increase in the risk of caesarean section in the BPP group. In addition, the increase in the rate of induction of labour … highlights the need for careful evaluation of the impact of the BPP.16

Fetal Movement Counting

With fetal movement counting, the pregnant woman or birthing person keeps track of the baby’s activity level. The rationale is that reduced movement could indicate a need to conserve energy. Reduced movement is reported to the care provider for further evaluation. A review concluded:

Women instructed on fetal movement counting had no difference in [stillbirths or newborn deaths] compared with those who did not receive instructions. The only … findings were marginally increased rates in preterm birth, induction of labor, and cesarean delivery.3

Does Fetal Surveillance Testing Prevent Stillbirths and Newborn Deaths?

We’ve seen that none of these tests achieve their goal. What’s more, the studies in the reviews of nonstress tests, amniotic fluid volume estimation, and fetal movement counting included high-risk pregnancies, and the review of the biophysical profile was exclusively of studies of high-risk pregnancies.3, 8, 16, 20 If tests screening for fetal well-being don’t reduce stillbirths or newborn deaths in populations including or restricted to high-risk pregnancies, they surely wouldn’t reduce them in low-risk pregnancies, in which babies would be much less likely to be in trouble.

Do Fetal Surveillance Tests Have Harms?

As these quotes make clear, fetal surveillance testing increases the probability of inductions and cesareans. Inductions and cesareans have potential harms and should only be used when their benefits outweigh their risks. However, as these quotes have also made clear, fetal surveillance tests don’t provide the promised benefit.

In Summary

Routine testing to evaluate fetal well-being fails to avert adverse outcomes while increasing inductions and cesareans and therefore the risk of experiencing their potential harms.

Your Takeaway

So, now you know that fetal surveillance tests don’t accurately identify babies at risk and that they lead to avoidable inductions and cesareans. In this section, I’ll offer tips depending on (1) you’re thinking of declining routine fetal surveillance testing, (2) you’re on the fence, or (3) you’ve undergone testing, and now your care providers are recommending inducing labor.

You Wish to Decline Fetal Surveillance Testing

Here are a couple of considerations if that is your choice:

  • Declining testing could put you at odds with your care providers. Your care providers are likely to believe that fetal surveillance tests are a vital tool for detecting babies in trouble. Saying “no” to them could have serious repercussions for your relationship. You’ll want to factor that into your decision.
  • Is this your first baby? If it is, and the test indicates a problem, inducing labor is much more likely to lead to a cesarean than when there has been a prior vaginal birth.2, 11, 13-15, 28 That may weigh in your evaluation of the pros and cons of declining testing as well.

You Aren’t Sure What You Want to Do

If you are on the fence but inclined to agree, my recommendation is to agree and be thoughtful about interpreting results. Yes, the research fails to find that fetal surveillance testing reduces mortality, but considered as part of an overall picture, it may still prove of use. Repeating a test if the result suggests there’s a problem reduces the probability of a false-positive result. And a single finding that slightly deviates from normal may not be concerning while finding an increasing trend in the wrong direction with serial testing or finding it in combination with other suboptimal maternal or fetal factors would be more worrisome.

If you’re agreeing to testing, here are some tips to minimize a false-positive diagnosis:

  • Non-stress test: The baby’s heart rate may not react to your uterus tightening or not be moving because the baby is asleep. Vibroacoustic stimulation can wake the baby up.1
  • Amniotic fluid volume estimation:
    • How the fluid volume is calculated matters. Ask whether it is estimated using the “maximum vertical pocket” technique or the “amniotic fluid index.” Be more skeptical of results if it is the amniotic fluid index. A systematic review of studies comparing the two techniques found that the vertical pocket technique was less likely to diagnose insufficient amniotic fluid compared with the amniotic fluid index (8% vs. 19%).25 Rates of poor condition at birth and admission to newborn intensive care nursery, however, were virtually identical, which means the additional diagnoses using the amniotic fluid index were false positives.
    • Hydration matters: Don’t go crazy, but make sure you’re well hydrated in the days before and the day of an amniotic fluid volume evaluation. Amniotic fluid volume is dynamic and is affected by your level of hydration.29

Your Care Provider Is Recommending an Induction

Finally, if inducing labor is recommended, here are some data-based strategies to discuss with your care providers that maximize the chances of an induction going smoothly and ending in a vaginal birth:

  • Especially if this is a first baby, in the absence of an acute medical problem, wait for a favorable cervix. Studies consistently find that compared with labor starting on its own, inducing first labors with an unfavorable cervix substantially increases the likelihood of cesarean despite use of cervical ripening agents.6, 7, 17, 18, 27 Once the cervix is ready for labor, cesarean rates are similar.
  • If the cervix is favorable, go straight to oxytocin. Cervical ripening agents aren’t necessary and omitting them avoids the possibility of experiencing their adverse effects.
  • Use an oxytocin protocol that “starts low and goes slow.” Equally high vaginal birth rates can be achieved with fewer adverse effects than with more aggressive regimens.5, 9 The Pitocin package insert includes a recommended regimen.
  • Refrain from rupturing membranes before active labor. If membranes are intact and the induction isn’t working, it can be stopped and tried another day. Once membranes are ruptured, that’s no longer an option, which means increased probability of cesarean for induction failure. Also, if there is concern about the baby’s ability to tolerate labor, the amniotic fluid cushions the umbilical cord and the baby from the pressure of contractions because you can’t compress a liquid. Release the fluid, and that protection is gone.22
  • Turn off the oxytocin drip once labor reaches active phase. In many cases, when the drip is turned off, labor will continue under its own steam. If it doesn’t, the drip can always be turned back on.24 Discontinuing oxytocin decreases likelihood of abnormal contractions and abnormal fetal heart rate and increases likelihood of vaginal birth.12
  • Have patience. Induced labors tend to take longer than labors that start on their own,4, 10, 21, 23, 26, 27 especially at first births, but longer labors don’t result in worse maternal or newborn outcomes.4, 26 

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References

  1. Antepartum Fetal Surveillance: ACOG Practice Bulletin, Number 229. Obstet Gynecol 2021;137(6):e116-e27.
  2. Baud D, Rouiller S, Hohlfeld P, et al. Adverse obstetrical and neonatal outcomes in elective and medically indicated inductions of labor at term. J Matern Fetal Neonatal Med 2013;26(16):1595-601.
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