CCM ~ Technical Bulletin 2-A: Background Information on Episodic & Continuous EFM & IA

by faithgibson on August 20, 2018

Draft ~ California College of Midwives

Principles and ‘Best Practices’ associated
with Physiological Childbirth Services

Technical Bulletin 2-A

Episodic & Continuous Electronic Fetal Monitoring (EFM) and how this information informs the use & interpretation of Intermittent Auscultation (IA)

Background Information and Principles of EFM

The Verbs and Nouns of Fetal Monitoring

Before addressing the technical questions of EFM, it must noted that fetal “monitoring” is first and foremost a VERB – that is, an activity done by professional labor and birth attendants to gather information on the rate and pattern of the fetal heart rate (i.e. pulse). The nouns associated with the activity of fetal monitoring include simple and inexpensive as well as very complex and expensive machines.

This can be done simply, directly and without the need for any equipment (either manual or electronic) by placing the practitioner ear directly on the mother’s pregnant abdomen and using a wristwatch or clock to count the rate and pattern of an unborn baby’s pulse. Other simple manual equipment incudes a wooden Pineard “horn” (looks like an ‘ear trumpet’) and a specially designed stethoscope called as a ‘fetoscope’. Non-continuous electronic monitoring can also be done with handheld electronic Doppler.

Under such circumstances, the birth attendant would first palpate the pregnant woman’s abdomen to identified the baby’s position in the uterus — fetal lie (head up or head down), and fetal position relative to the mother’s pelvis and which side of the mother’s abdomen one would expect the baby’s chest to be on, which is where the birth attendant would begin listening for fetal heart tones.

In the 1970s, an electronic machine was developed that continuously count the number of fetal heart pulses (heartrate) and to electronically graphic both the rate and pattern of the fetus’s pulse on a moving graph paper, as well as a constantly renewed electronic digital display on the face of the machine.

Primary Sources of Information 

The primary source for educational material in this section comes from a book entitled “Fetal Monitoring In Practice” by Doctors David Gibbs & S. Arulkumaran. These two obstetricians, one from London, England and the other from Singapore, are consultants for a major public hospital in Singapore that has 26,000 births per year and enjoys a “shared maternity care” system — that is, a healthcare system in which midwifery is normative.

These authors are specifically supportive of midwifery care for hospitalized patients of all risk levels (in collaboration with physicians) and they adhere to the WHO guidelines for promoting safe motherhood, which are:

  • To optimize the health of the mother,
  • To optimize the health of the offspring
  • To optimize the emotional satisfaction of the mother and her family.

These obstetricians go on to say that:

Excessive technology should not be applied to those who are manifestly at low-risk. It may confer no benefit, can generate both non-medical and medical anxiety and through subtle effects may cause significant harm. Such unthinking application is counter- productive.

A relationship of trust and professionalism should bear fruit. It is acknowledged that the introduction of EFM has contributed to an increase in the number of cesarean birth. This is largely due to failure to understand the principles of the technique, but may also be attributed to a fear of litigation. Both can be effectively countered.”

Referring to the nature of maternity care and status of childbearing women they say:

“… are unique in that they are not sick. On the contrary, they are experiencing one of the most important events of their lives with enormous emotional impact. The intimacy of this experience should not be compromised except in the genuine interest of safety for mother and child. This information should help us recognize the ‘genuine interest’. Without this we will not earn the approbation of those who have entrusted their care to us. ” Dr. David Gibbs & S. Arulkumaran, MD

In spite of caring for more than 26,000 laboring women every year, these physicians had only two EFM machines available. Since it was impossible to use continuous electronic monitoring on every labor patient, obstetricians had to develop methods for determining who needed or would most benefit from continuous electronic monitoring and who were better served by intermittent auscultation (IA).

As a result, they developed an excellent good understanding and practical guidelines for IA and episodic EFM, which are fully explored in these two technical bulletins on the principles and practice of EFM within the midwifery model of care and community-based childbirth services.

A New Way of Thinking and its New Vocabulary

Doctor Gibbs and Arulkumaran believe the expression ‘fetal distress’ should be reconsidered and a different vocabulary developed.

An EFM trace that is not normal may be the result of physiological, iatrogenic or pathological causes, meaning that the so-called distress of the fetus may be a healthy stress response — i.e. not an indication of pathological distress.

So-called ‘fetal distress’ may be provoked either by improper care or may indicate a problem originating within the fetus. The clinical situation and the dynamic evolution of clinical features being displayed on the EFM trace will clarify the situation with time. The underlying principle is to detect fetal compromise using the concept of fetal distress very critically. Carefully consideration of the overall clinical picture will, in the vast majority of situations, provide the clues to whether fetal compromise is present, and, if appropriate, allow caregivers to rectify situations of their own making (iatrogenic factors arising from medical interventions, administration of drugs, etc).

Many intrapartum EFM tracings that are concerning to professional care providers are generated by a healthy fetus demonstrating a healthy ability to respond to normal biological stresses encountered during an otherwise normal labor, or introduced by medical treatments or intervention (i.e., iatrogenic in origin).

Cesarean surgery should not be used to treat caregiver distress resulting from a misunderstanding of EFM principles or to reduce caregiver anxiety over a EFM tracing that is not reassuring. The purpose of monitoring (of all kinds) is to guard the baby’s well-being — not primarily to protect professional caregivers from possible criticism by others or litigation at a later time.

Pattern Recognition & Documentation

EFM takes advantage of the fact that human being are better at and much happier with pattern recognition that they are computing. EFM does the math and prints out the pattern, which is one of the reasons that it is so popular in the medical community.

The next step in dealing intelligently with EFM information is to systemize the information provided by episodic EFM (baseline and presence or absence of acceleration and decelerations by charting this data on a graph flow sheet,

For midwives using IA, this same concept is employed by charting the FHR and associated patterns detected by intermittent auscultation (IA), which transfers the audible variability heard and counted by the labor and birth attendant into visual pattern with a numerically-defined bandwidth*.

(*See Intermittent Auscultation Long-term Variability form on the back of the Intrapartum flow sheet and Technical Bulletin No. 1).

Technical aspects of Electronic Fetal Monitoring

The numbers generated by EFM compute the rate (or pulse) of the unborn baby based on averaged intervals between beats extrapolated to what the rate would be if the beat intervals remained constant for an entire minute. In other words, a read out of 60 or spikes to 180 bpm does not actually represent a heart rate of 60 or 180 bpm unless this rate stays constantly up or down for one full minute or longer.

Most up-to-date monitors re-compute the rate every 2 seconds. Autonomic nerve impulses of the fetus immediately and constantly take effect, changing the beat intervals and immediately altering the heart rate. This is how baseline variability is generated and it indicates the integrity of the autonomic nervous system. Baseline variability is actually seen on the tracing (or heard with IA).

Mechanical or electrical interference / artifacts: Old EFM machines without auto-correction may give the appearance of false baseline variability by having a lots of up and down spikes that reflect maternal motion — not fetal heart action. Old fetal monitors are not reliable for determining variability as they can erroneously create the appearance of variability where none exists.

Another form of mechanical interference is cause by poor contact between the baby and a scalp electrode. This creates a “picket fence” pattern — constant sharp ascending and descending vertical lines that tract the baseline. It also will sometimes half the rate or give an irregular rate. Newer monitors are more reliable with external system that the older scalp electrodes. The newest versions still give unreliable information in the internal monitoring mode if they are not making good contact between the fetus, the scalp electrode and the mother’s body.

Other Electrical Interference / TENS: Extraneous electrical influence can produce artifacts in the baseline variability (BLV). If the electrical disturbance exceeds the frequency of signals obtained from the FHR using a scalp electrode it can completely confuse the FHR signal resulting in no FHR tracing. The use of transcutaneous electrical nerve stimulation — a TENS stimulator — of the obstetrical pulsar used for pain relief can produce this problem. TENS external ultrasound monitoring is preferred.

False baseline because of characteristics of EFM technology which erroneously doubles the true cardiac rate: In normal circumstances the atrium and ventricle chamber of the fetal heart beat almost simultaneously followed by the next complete cardiac movement of these chambers. This describes the healthy action of the heart and is the mechanism upon which the ultrasound depends for calculating a baseline fetal heart rate. The reflected ultrasound from these two chambers or even from one of the walls (atrium, ventricle or the valves) is used by the machine to compute the FHR.

When the FHR is slow (70-80 bpm) there is a longer time interval between the atrial and ventricle contraction. The machine recognizes each of the reflected sound (one from the ventricle and the other from the atrium) as two separate beats and computes the rate, which may mimic a normal FHR, as it will be in the expected range for a normal baseline. For most observers the sound generated will also give an impression that the FHR is within the normal range (WNR) because the heart sounds from the machine are always the same for every baby — they are electronic noise (a canned sound built into the circuitry and triggered by each pulse of ultrasound).

During the false counting or ‘doubling’ of the FHR episode, listening with a fetal stethoscope or Doppler will reveal the true situation. The suspicion that something is amiss will be aroused by the FHR tracing, which may show a stretch of baseline reading, for example of 140 bpm, but at other times will record a rate half that (70bpm).

Because it is a double counting phenomenon the upper rate on the recording paper will be exactly double that of the lower rate and can be easily checked by auscultation. Such a trace can also be due to the machine recognizing an atrial rate of 140 bpm and a ventricular rate of 70 bpm at different times in a case with complete heart block. The mother in these instances may have an autoimmune disorder. These circumstances would be an indication for use of fetal electrode.

Continue to Technical Bulletin 2-B