EFM - Electronic Fetal Monitoring Fetal Heart Rate Variability Questions and Answers — Questions and Answers
Question 1: A nurse is evaluating an electronic fetal monitoring (EFM) strip and notes the variability is consistently greater than 25 beats per minute (bpm) from the baseline. According to NICHD guidelines, how should this fetal heart rate variability be classified?
- Moderate
- Minimal
- Marked (Correct answer)
- Absent
Correct answer: Marked
According to the National Institute of Child Health and Human Development (NICHD) guidelines, fetal heart rate variability is classified as marked when the amplitude range from peak to trough is greater than 25 bpm. Moderate variability is 6-25 bpm, minimal is detectable but ≤5 bpm, and absent is an undetectable amplitude range.
Question 2: An EFM tracing shows a baseline fetal heart rate of 140 bpm with an amplitude range of 2-3 bpm for the past 40 minutes. The patient denies receiving any recent medications. Which of the following is the most likely cause for this pattern?
- Maternal fever
- Fetal sleep cycle (Correct answer)
- Umbilical cord compression
- Uteroplacental insufficiency
Correct answer: Fetal sleep cycle
Minimal variability (amplitude range detectable but ≤5 bpm) that lasts for a limited time is often due to a normal fetal sleep cycle, which typically lasts 20-40 minutes. While other conditions like hypoxemia can cause minimal variability, a fetal sleep cycle is a common and benign cause for this specific duration without other non-reassuring signs. Maternal fever usually causes tachycardia, and cord compression or uteroplacental insufficiency would likely present with decelerations.
Question 3: Which of the following is the single most important characteristic of the fetal heart rate that reliably predicts the absence of fetal metabolic acidemia at the time of observation?
- Presence of accelerations
- A baseline rate of 110-160 bpm
- Absence of decelerations
- Presence of moderate variability (Correct answer)
Correct answer: Presence of moderate variability
The presence of moderate variability (6-25 bpm) is highly predictive of a normal fetal acid-base status and the absence of significant fetal metabolic acidemia at that specific time. It reflects an intact central nervous system and adequate oxygenation. While a normal baseline, accelerations, and absence of decelerations are reassuring, moderate variability is considered the most reliable indicator of fetal well-being in this context.
Question 4: A laboring patient's EFM tracing displays an undulating, smooth, sine wave-like pattern with a frequency of 3-5 cycles per minute and an amplitude of 5-15 bpm that has persisted for 20 minutes. What condition is most commonly associated with this ominous pattern?
- Maternal sedation
- Fetal cardiac arrhythmia
- Severe fetal anemia (Correct answer)
- Fetal hiccups
Correct answer: Severe fetal anemia
A true sinusoidal pattern is a rare and ominous finding. It is characterized by a smooth, sine wave-like pattern with a frequency of 3-5 cycles per minute, persisting for at least 20 minutes. This pattern is most commonly associated with severe fetal anemia, often from conditions like Rh isoimmunization or significant fetal hemorrhage.
Question 5: A nurse observes a change in the fetal heart rate variability from moderate to absent on the EFM tracing, which persists despite intrauterine resuscitation measures. This change is most concerning for the development of which fetal condition?
- Fetal metabolic alkalosis
- Transient fetal hypoxemia
- Fetal metabolic acidemia (Correct answer)
- Compensated respiratory acidemia
Correct answer: Fetal metabolic acidemia
Persistent absent variability is a non-reassuring sign that is strongly associated with fetal metabolic acidemia. The acidemia depresses the fetal central nervous system (CNS), leading to the loss of the normal push-and-pull effect of the sympathetic and parasympathetic nervous systems, which creates variability. Transient hypoxemia might cause minimal or marked variability initially, but persistent absent variability suggests a more severe, decompensated state.
Question 6: Which of the following interventions or conditions is LEAST likely to cause a decrease in or absence of fetal heart rate variability?
- Administration of magnesium sulfate
- Fetal acoustic stimulation (Correct answer)
- Fetal sleep state
- Administration of narcotic analgesics
Correct answer: Fetal acoustic stimulation
Fetal acoustic stimulation is a method used to elicit an acceleration in the fetal heart rate, which demonstrates fetal well-being. It is intended to stimulate the fetus, often increasing activity and variability, not decrease it. In contrast, medications like magnesium sulfate and narcotics, as well as normal fetal sleep cycles, are all well-known causes of decreased or minimal FHR variability.
EFM - Electronic Fetal Monitoring Fetal Heart Rate Variability Questions and Answers
A nurse is evaluating an electronic fetal monitoring (EFM) strip and notes the variability is consistently greater than 25 beats per minute (bpm) from the baseline.
According to NICHD guidelines, how should this fetal heart rate variability be classified?