fetal surveillance.

When it comes to “fetal surveillance,” the primary objective is to prevent the death of the newborn. Fetal assessment most often takes place near the end of pregnancy, particularly when a woman goes beyond her due date.

Several techniques are used to assess fetal well-being, including:

• Non-stress testing

• Contraction stress testing

• Biophysical profiles

• Placental grading through ultrasound

• Fetal movement counting

Fetal heart rate testing has evolved over a period of more than 30 years, and debate about how to classify fetal heart rate patterns has continued throughout that time.

Studies of fetal heart rate monitoring—including both non-stress tests and contraction stress tests—have been conducted over a ten-year period. Overall, the chief value of fetal heart rate testing is its ability to identify the normal, healthy baby. These tests are less accurate when it comes to identifying a sick or compromised baby.¹

This raises an important question: Are these tests truly of clinical significance?

And what about the exposure of large numbers of healthy babies to repeated ultrasound examinations? Is it all necessary? Can it truly prevent tragic outcomes?

Pregnancy and birth offer no absolute guarantees. Clinical testing should not be administered so routinely without carefully considering both its effectiveness and its potential risks.

The Non-Stress Test

In a non-stress test (NST), the baby is monitored using ultrasound while fetal heart rate and movement patterns are recorded.

Unfortunately, this test has a fairly high rate of false positive results. One reason for this is that babies in the womb spend much of their time asleep.

Babies in utero cycle through several states:

• A quiet sleep state

• An active sleep state

• A state characterized primarily by eye movements

When the baby is awake and active, movement produces accelerations and variability in the fetal heart tracing. However, because babies are asleep approximately 70 percent of the time in utero, false non-reactive results frequently occur during non-stress testing.

If the baby is asleep, there are often few accelerations or changes in heart rate variability. This can lead to a false positive result, incorrectly suggesting that the baby’s well-being is compromised.²

Another concern is that the non-stress test requires prolonged exposure to ultrasound.

Acoustic Stimulation: A Simpler Alternative

One alternative to non-stress testing is the fetal acoustic stimulation test (AST).

This test involves placing a brief sound stimulus—lasting one to two seconds—on the lower abdomen. The sound stimulates the baby and often causes the baby to awaken, producing the expected accelerations and variability in heart rate.

If necessary, a second stimulus may be applied within ten minutes of the first.

Studies have shown that sound-induced accelerations in fetal heart rate are reliable predictors of fetal well-being.³

When non-stress testing was compared with acoustic stimulation, researchers concluded that AST offered several advantages, including:

• A lower rate of non-reactive results

• Shorter testing time⁴

The use of this simple technique could greatly reduce the need for contraction stress testing.

Contraction Stress Testing

The contraction stress test requires the baby to be monitored electronically while the mother receives an oxytocin infusion through an intravenous line in order to stimulate contractions.

This test is associated with a higher rate of medical intervention.⁵

If simpler methods such as acoustic stimulation are effective, the need for more invasive procedures like contraction stress testing could be significantly reduced.

The Biophysical Profile

Another common assessment tool is the biophysical profile (BPP), often used when pregnancies go beyond their due date.

The goal of managing post-term pregnancies medically is to avoid neonatal death or stillbirth. However, an important question remains: Is this truly possible, and at what cost to both mother and baby?

The biophysical profile evaluates five characteristics of the fetus:

• Fetal movement

• Fetal muscle tone

• Fetal breathing movements

• Heart rate reactivity

• Amniotic fluid volume

Ultrasound is used to assess fetal movement, tone, breathing, and amniotic fluid volume. Electronic monitoring is used to evaluate heart rate reactivity.

Overall fetal well-being is then judged based on multiple variables, including:

• The size of the baby

• The amount of amniotic fluid

• Non-stress test results

• The complete biophysical profile

However, the predictive accuracy of these tests is limited. The biophysical profile has only 18 percent sensitivity for predicting poor outcomes, while the non-stress test has about 14 percent sensitivity.⁶

When biophysical profiles are used, there is also a small risk of iatrogenic prematurity—premature birth caused by medical intervention—occurring in approximately 1.5 percent of cases due to false positive results.⁷

Amniotic Fluid Measurement

Assessing amniotic fluid volume is commonly used to evaluate fetal well-being. However, problems arise when even major obstetric textbooks define “normal” amniotic fluid levels differently.⁸

The uterus itself varies greatly in shape and size between women, which makes precise measurement difficult.

Three ultrasound techniques are typically used:

• Maximum vertical pocket measurement

• Subjective assessment

• Amniotic fluid index (AFI)

Despite their widespread use, amniotic fluid measurements have been shown to be unreliable predictors of fetal well-being or neonatal illness.⁹

Studies have demonstrated that ultrasound assessments such as the amniotic fluid index and two-dimensional pocket measurements do not accurately reflect the true volume of amniotic fluid.¹⁰

Furthermore, measuring amniotic fluid late in pregnancy using these techniques has been shown to be a poor predictor of adverse newborn outcomes.¹¹

Reference ranges for the amniotic fluid index may also overestimate the number of abnormal results in pregnancies that extend beyond the due date.

When a test is accurate only 50 percent of the time in identifying low amniotic fluid levels, it should not be the sole reason for inducing labor when a pregnancy extends past the due date.¹²

Such findings are likely to increase the number of invasive obstetric interventions.¹³

The Cascade of Intervention

Women are often told that they have “too little” amniotic fluid, even though reliable testing methods may not support this conclusion.

Interventions such as induction with medications like Pitocin or Cytotec frequently follow. These inductions can lead to additional procedures, including:

• Forceps delivery

• Vacuum extraction

• Cesarean section

Ironically, these interventions may create complications rather than prevent them.

The high rate of inaccurate findings combined with the risks of intervention may outweigh the benefits of routine testing.

Women who receive abnormal biophysical profile scores are four times more likely to deliver by cesarean section.¹⁴

Research has also shown that 60 percent of babies delivered because of abnormal antepartum testing results were actually healthy at birth, showing no evidence of fetal compromise.¹⁵

These findings suggest that such tests cannot be considered conclusive indicators of fetal distress.

As recently as the year 2000, there was still insufficient evidence to fully evaluate the usefulness of the biophysical profile as a predictor of fetal well-being.¹⁶

Even after 42 weeks of pregnancy, the biophysical profile has not been shown to improve pregnancy outcomes.¹⁷ Yet its use continues and remains widely accepted in modern obstetrics.

Placental Grading

Placental grading is another term commonly heard by women nearing their due date. Physicians often use ultrasound to assess the “maturity” of the placenta and determine whether it can continue to support the baby.

Placental grades are typically classified as:

• Grade 0 – least mature

• Grade I

• Grade II

• Grade III – considered post-mature

However, when 654 pregnant women were evaluated using placental grading, fetal outcomes were not associated with these classifications. A Grade III placenta did not predict adverse outcomes.¹⁸

As a result, the usefulness of placental grading in monitoring post-term pregnancies has been questioned.¹⁹

Another study involving 85 pregnant women found that Grade II and Grade III placentas occurred with similar frequency. Researchers concluded that placental grading cannot reliably predict post-maturity.²⁰

A Simpler Indicator: Fetal Movement

Despite the complexity of modern fetal surveillance techniques, a simple method may provide valuable reassurance.

A mother can gauge her baby’s well-being by counting fetal movements.

When babies move and kick in the womb, mothers are reassured that all is well. Conversely, the absence of fetal movement is strongly associated with fetal demise.

One commonly used movement-counting method involves selecting a time each day to record how long it takes to feel ten fetal movements.²²

A woman should contact her care provider if:

• Fewer than ten movements are felt within ten hours

• No movement is felt during a ten-hour period

In reality, most women can feel ten movements much sooner—often within ten minutes.

Fetal movement counting allows women to remain closely connected to their babies while also providing meaningful reassurance about the baby’s well-being.