FETAL MONITORING

SUMMARY: Electronic Fetal Monitoring (EFM) performs poorly but remains routinely used. Economic and defensive factors explain its continued usage. Interpretation of EFM tracings is still controversial and should rarely be central to litigation strategy.

Preventing birth asphyxia and obstetric brain damage is a major focus of obstetric care.

Predicting which fetuses are at risk during labour has always been, and remains, an inexact science.

EFM was developed in the 1950s to provide such surveillance, largely as a result of animal research.

The test was introduced into clinical practice in North America in the late 1960s and was rapidly and extensively adopted.

Efficacy

Electronic Fetal Monitoring (EFM) performs poorly but remains routinely used.

As a method of assessing fetal health during labour, Electronic Fetal Monitoring (EFM) has not fulfilled its early promise.

It is a poor screening test that became standard clinical practice before it was properly evaluated.

Current evaluation¹by Evidence Based Medicine's is that the only clinical benefit of routine EFM is a decrease in neonatal seizures.

This gain has been achieved at the expense of a considerable increase in rates of cesarian section and operative vaginal delivery.

Moreover, the benefit to the newborn infant's health was seen only when EFM was combined with Fetal Blood Sampling (FBS)² ^[] - checking scalp blood acidity. Since FBS can identify the minority of non-reassuring EFM recordings^2a that actually reflect fetal compromise^{2b
[]}, this procedure arguably represents the current Standard of Care.

If the decrease in neonatal seizures was reflected in materially less obstetric brain damage, the price might be worth paying.

However, the definitive results of that research are not yet available, and preliminary results suggest little if any advantage.

Specifically, no quality study has found a decrease in the occurrence of cerebral palsy following labours that were monitored electronically rather than intermittently by fetal stethoscope (auscultation).

A recent review paper³ ^[]concluded, "There is no evidence that caesarean section [based on EFM] can prevent cerebral palsy in term infants."

As early as 1979 there were official US recommendations⁴ to employ EFM only in conjunction with FBS and this was echoed in the UK⁵ in 1993 and, for clarification of abnormal EFM patterns, by a Canadian authority^5a in 1999 and Clinical Practice Guideline^5b in 2002.

Practice Point

Electronic Fetal Monitoring is no longer recommended for routine use, even for high-risk pregnancies

Expert panels in both the US⁶ and Canada⁷ have advised against the use of EFM in low-risk pregnancies and have found only weak evidence for or against routine use in high-risk pregnancies.

Why is it still used?

Yet Electronic Fetal Monitoring remains entrenched in routine management of labour and delivery.

Economic and defensive factors explain its continued usage.

Part of the explanation is that younger nurses and obstetricians lack the experience and skill in interpreting fetal heart sound patterns heard with the stethoscope.

Moreover, auscultation is considerably more time-consuming and therefore probably requires a ratio of one nurse for every labouring mother⁸.

A major factor is fear of successful medical malpractice litigation if there is no reassuring EFM tracing to justify the failure to intervene in a labour with an adverse outcome.

Of course, the irony is that EFM tracings that have arguably non-reassuring features are used to advance medical malpractice claims, despite the low predictive power of EFM.

EFM Interpretation

Interpretation of EFM tracings is still controversial and should rarely be central to litigation strategy.

Plaintiff and defence counsel need to be aware that interpretation of EFM tracings is not only subject to considerable disagreement between experts^9,10, but is also influenced¹¹ by hindsight bias.

Reviewers who were given identical EFM tracings and antenatal histories were more likely to disagree with the obstetrician's interpretation if they were told that the outcome was poor¹².

Practice Point

Interpretation by reviewers is susceptible to hindsight bias

Where difference in medical expert opinion is materially caused by disagreements about EFM interpretation, internationally-agreed criteria¹³ are available for arbitration.

In the absence of bradycardia - a fall in the baseline fetal heart-rate to below 110-120 beats per minute, the criteria for non-reassuring EFM patterns involve only variability and decelerations.

Variability refers to the change in amplitude of beat-to-beat complexes - jaggedness of the fetal tracing - and is designated absent, minimal (up to 5 beats per minute, bpm), moderate (6-25 bpm) or marked (more than 25 bpm).

A late deceleration of the fetal heart-rate is a gradual decrease in the baseline rate such that the nadir of the curve occurs after the peak of the uterine contraction.

A prolonged deceleration is a baseline decrease of at least 15 bpm lasting 2-10 minutes.

Practice Point

With rare exceptions, Electronic Fetal Monitoring patterns cannot predict birth asphyxia or obstetric brain-damage

Canadian researchers have proposed that the only patterns that are predictive of fetal asphyxia are at least 2 late or prolonged decelerations in the context of absent or minimal variability ¹⁴ ^[]. Lesser occurrences of these non-reassuring patterns are considered suspect.

Canadian medical defence frequently employs the senior author of this clinical research paper as medical expert witness on Causation in such circumstances.