Electronic Fetal Monitoring: What is it and Why is it Important to the Safety of Your Baby?

One of the most devastating injuries that your baby can suffer in the uterus is called neonatal encephalopathy. Neonatal encephalopathy is usually caused by hypoxic ischemic encephalopathy (HIE).

HIE happens when your baby’s brain does not receive enough oxygen. This can be caused by:

  • Ischemia: when there has been a restriction of blood flow to the brain (for example when the umbilical cord becomes crimped); or
  • Hypoxia: when there isn’t enough oxygen in the bloodstream from any cause (for example problems like a detached placenta).

The most important tool that doctors and nurses use to measure your baby’s oxygenation during labour and delivery is the Electronic Fetal Heart Monitor (EFM).

What does the EFM do?
The Society of Obstetricians and Gynecologists of Canada point out that the purpose of fetal heart monitoring is to:

“detect potential fetal decompensation and to allow timely and effective intervention to prevent perinatal/neonatal morbidity (this means injury) or mortality (death).”

Your baby’s heart rate reacts to the presence or absence of oxygen in the body. There are certain patterns that are reassuring and indicate a healthy baby. There are other patterns that may or may not be concerning depending on the clinical circumstances.

Finally, there are some patterns that are obvious signs of risk or danger to the baby. Doctors and nurses use electronic fetal monitoring to determine when your baby may be at risk and may require an expedited delivery by caesarean section or operative vaginal delivery.

How does the EFM work?
The EFM monitor has two devices that detect pressure called transducers. The transducers are placed on your abdomen and held in place with straps. From time to time it may be necessary for the nurses to adjust or move the transducer’s in order to achieve an adequate signal to produce a clear and continuous heart rate on the recording strip.

The EFM has a screen or monitor that shows the fetal heart rate. The EFM also produces a printed strip of paper that is covered in grids showing time segments and heart rate. Data from the EFM monitor is plotted on the strips and looks like two wavy or spiky lines A properly trained professional can tell a great deal about the wellbeing of your baby during labour by looking at the lines on the EFM strips.

The top line of the EFM strip represents the fetal heart rate. The line spikes up (peaks) or dips down to reflect changes in your baby’s heart rate.

The bottom line of the strip shows the mother’s (your) uterine contractions. The line spikes up (peaks) when you are having a contraction.

When these two lines are looked at in conjunction with one another, properly trained nurses and doctors can learn a great deal about the health and well-being of your baby.

EFM monitors also produce sounds that are related to the fetal heart rate. The machines also have alarms that are supposed sound when the fetal heart rate gets too fast or too slow.

Understanding EFM Data
It is important that the nurse and physicians that are treating you are properly trained in the use and interpretation of EFM data. There are a number of different factors that the EFM monitor will record that are critical to evaluating your baby’s health and well-being.

Contractions: One of the transducers measures the pressure produced when you have contractions during labour. The EFM will detect the duration of your contraction (how long it lasts) and the frequency of your contraction (how many times you’re having contractions in a ten minuet period). The nurses or doctors that are monitoring your labour will measure the intensity of the contractions by palpating (feeling) your belly.

During normal labour the duration of your contractions should be about 40-60 seconds. Contractions that last longer than two minutes are abnormal and are referred to as “hypertonus”.

The frequency of your contractions should be about two to three minutes apart. When you have contractions that come more frequently than one every two minutes it is called tacysystole. The risk of tacysystole increases when your physicians use certain drugs like oxytocin to try to induce or assist your labour.

Fetal Heart Rate Patterns
The EFM tracks a great deal of information that your health care providers will consider and use in making a determination about whether your baby is doing well during the labour (reassuring patterns) or if your baby is struggling (non-reassuring patterns).

The Society of Obstetricians and Gynecologists of Canada has established guidelines defining the important data collected by the EFM.

Baseline Heart Rate:

The baseline is, essentially, the average of how fast your baby’s heart is beating over a period of 10 minutes. When figuring out the average, your healthcare professional will exclude accelerations (spikes in your baby’s heart rate) and decelerations (dips in your baby’s heart rate) to come up with a baseline rate.

  • The normal baseline for a healthy fetus is between 110 to 160 beats per minute.
  • If you baby’s heart rate goes above 160 beats per minute for extended periods of time (more than 10 minutes) this is a condition known as tachycardia. Tachycardia can be a sign of fetal distress because when a baby’s heart is beating too quickly, blood is not being circulated as efficiently which can lead to oxygen deprivation.
  • When the heart rate drops below 110 beats per minute this is called bradycardia. Bradycardia is also a sign of fetal distress. It usually means your baby is not getting enough oxygen.

Heart Rate Variability

Verifiability refers to the spikes above the baseline and dips below the baseline. A healthy baby’s heart rate usually fluctuates over time so it is normal and reassuring to see variation in the heart rate over time.

  • If the spikes or dips in the heart rate are greater than 25 beats per minute the variation is classified as marked.
  • Variability that ranges between 6-25 beats per minute is classified as moderate.
  • Variation of less than 5 beats per minute is classified as minimal.
  • When the baby’s heart rate is traced essentially as a flat line the variability is classified as absent.

A healthy fetus will normally produce a heart rate with moderate variability. Any significant reduction in variability can be a cause for concern.

There are some conditions that can cause reduced or absent variability that aren’t life threatening. For example, if the mother has been given pain medication that may decrease the fetal heart rate variability. Sometimes the fetus will fall asleep during labour and this will also result in a pattern of reduced variability.

The health care professionals that are monitoring your labour will need to consider all the clinical circumstances and medical evidence to determine whether reduced variability is something that is normal and not of any concern or whether the reduced variability is a non-reassuring sign of potential fetal distress.

  • Accelerations: Sometimes the EFM monitor will show abrupt spikes in the heart rate. Any abrupt increase in the heart rate of more than 15 beats per minute is referred to as an acceleration. Accelerations are a normal reassuring sign that your baby is doing well.
  • Decelerations: A dip in the heart rate below the baseline is referred to as a deceleration. There are a number of different patterns of decelerations some of which are normal and others which can be signs of fetal distress.
  • Early decelerations are a gradual decrease in the fetal heart rate that typically mirrors the mother’s contractions. The decrease in heart rate is caused by head compression from the contraction and they are usually considered to be normal.
  • Variable decelerations are an abrupt drop in the fetal heart rate of more than 15 beats per minute lasting anywhere from 15 seconds to two minutes. Variable decelerations are commonly seen during labour and are thought to be caused by decreased oxygenation from cord compression. Variable decelerations are categorized as either uncomplicated or complicated.
    • Uncomplicated variable decelerations show an initial spike (acceleration) then a dip (deceleration) followed by another spike (acceleration) before the heart rate returns to the normal baseline. Uncomplicated variable decelerations are generally not concerning unless they start to happen repeatedly. Then they may be a sign of fetal distress.
    • Complicated variable decelerations may have loss of variability in the baseline or it may be a deceleration in two phases or it may be a deceleration that takes a long time to return to the baseline. Complicated variable decelerations are unusual and can be a sign of fetal distress.

Finally, a late deceleration is one where the bottom of the deceleration is after the peak (or tip) of the contraction tracing. Late decelerations are generally accepted by medical professionals to reflect some degree of hypoxia (oxygen deprivation) in the fetus.

EFM Classification
When your nurse or doctor looks at the EFM strip they have to consider all of the circumstances and all of the data on the monitor in order to classify the strip.

It used to be that EFM strips were categorized as either reassuring (the information on the monitor showed that the baby was doing well) or non-reassuring (the information on the monitor suggests the baby may not be doing well). Unfortunately this easy to understand classification system has been abandoned by the medical profession.

In recent years the Society of Obstetricians and Gynecologists of Canada have created new guidelines to categorize EFM strips as normal, a-typical or abnormal.

Normal EFM strips are considered to represent a well oxygenated fetus and are generally what used to be referred to as a reassuring strip. In other words, the baby is likely to be happy and healthy.

Abnormal strips contain data that strongly suggest that there are problems with fetal oxygenation and that the baby may be at risk of injury. Abnormal tracings usually require immediate action either to try to address the cause of the abnormal tracing or to expedite delivery of the baby by C-section or operative vaginal delivery.

Unfortunately, most EFM tracings fall into the a-typical category. These types of tracings suggest that there may or may not be a problem fetal well-being and the baby may or may not require expedited delivery. What the appropriate action is when faced with an a-typical tracing depends on a consideration of all of the clinical circumstances and is usually the subject of much debate in obstetric medical malpractice claims.

Expert Evidence
One of the first things that your obstetric medical malpractice lawyer will do will be to hire an expert to assess the fetal heart monitor tracings to determine whether there was any evidence of fetal distress and to determine whether your health care professionals’ reactions were appropriate.

Experienced obstetric malpractice lawyers are usually able to read or interpret EFM tracings to determine whether there are potential grounds for concern and whether it is appropriate for further investigation by hiring a medical expert.

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