Electronic Fetal Monitoring Test: Purpose, Test Details & Results

Purpose of Electronic Fetal Monitoring Test

Electronic fetal monitoring (EFM) is a widely used tool in modern obstetric care, designed to provide real-time information about a baby’s well-being during labor and delivery. The primary goal is to detect signs of fetal distress that could indicate inadequate oxygenation or other complications, allowing healthcare providers to act quickly to prevent negative outcomes. Despite its commonplace use, the effectiveness and interpretation of EFM remain subjects of ongoing research and debate.

Below, we summarize the key reasons for using EFM, its intended outcomes, and its limitations based on the latest scientific findings.

How EFM Aims to Protect Babies and Mothers

Screening for Fetal Distress
EFM tracks the baby’s heart rate alongside the mother’s contractions. By analyzing this data, clinicians hope to spot warning signs such as abnormal heart rate patterns or reduced variability, which may suggest the fetus is not getting enough oxygen 1 3 5. These early alerts can prompt timely interventions, such as changing the mother’s position, providing supplemental oxygen, or expediting delivery.

Reducing Risk of Adverse Outcomes
One of the primary aims of EFM is to decrease the likelihood of severe outcomes like metabolic acidosis—a condition where the baby’s blood becomes too acidic due to lack of oxygen—and long-term complications such as hypoxic-ischemic encephalopathy or cerebral palsy 1 3 4. However, research has shown that while EFM is associated with changes in delivery practices, its direct impact on reducing these serious outcomes is modest at best 1 4 7.

Supporting Clinical Decision-Making
EFM provides objective, continuous data that can help clinicians decide if and when to intervene. This is especially important in high-risk situations or when there are concerns about fetal compromise. For example, persistent abnormal patterns may indicate the need for a cesarean or instrumental delivery to protect the baby’s health 3 4 5.

Current Limitations and Evolving Perspectives

Interpretation Challenges
Despite its widespread use, EFM is not a perfect predictor of poor outcomes. Its interpretation is subject to human error and variability. Moreover, many abnormal patterns do not result in harm, while some cases of distress may go undetected 1 5 7. As a result, EFM can sometimes lead to unnecessary interventions, such as cesarean sections, without clear benefits 4 6 7.

The Future of EFM
Newer approaches, such as the Fetal Reserve Index or artificial intelligence-enhanced analysis, are being developed to improve EFM’s accuracy and usefulness. These aim to combine EFM data with other contextual information for a more comprehensive assessment 7.

Electronic Fetal Monitoring Test Details

Understanding the EFM process helps demystify what happens during labor and why the test is performed. EFM can be conducted externally or internally and involves continuous or intermittent monitoring of both the fetal heart rate and uterine contractions.

Here’s a summary of how the test is performed, what it measures, and its practical considerations.

Types of EFM and How They Work

External Electronic Fetal Monitoring

• Involves placing two sensors (transducers) on the pregnant person’s abdomen.
• One sensor monitors the baby’s heart rate using ultrasound technology.
• The other records uterine contractions via a pressure-sensitive device.
• Non-invasive and commonly used during labor 5 6.

Internal Electronic Fetal Monitoring

• Used when more precise information is needed, especially if external readings are unclear.
• A tiny electrode is attached to the baby’s scalp after the membranes have ruptured.
• A pressure catheter may be placed inside the uterus to measure contraction strength.
• Provides more accurate data but is slightly more invasive 5.

What EFM Measures and Records

• Fetal Heart Rate Patterns: Baseline heart rate, variability, accelerations (increases), and decelerations (decreases) 1 3 5.
• Uterine Contractions: Frequency, duration, and intensity.
• Responses to Contractions: How the baby’s heart rate changes in relation to contractions (late, variable, or prolonged decelerations can be significant) 1 3.

Interpreting the Patterns

EFM data are interpreted using standardized categories and criteria:

• Category I (Normal): Predicts normal fetal acid-base status.
• Category II (Indeterminate): Requires close monitoring; may be associated with evolving problems.
• Category III (Abnormal): Suggests increased risk for fetal acidemia; intervention often required 3.

Specific patterns—such as late decelerations, decreased variability, and tachycardia—can signal risk for fetal acidemia (too much acid in the blood) or hypoxic-ischemic encephalopathy (brain injury from lack of oxygen) 1 3.

Advances and Adjuncts

• ST-Segment Analysis: Some advanced systems add fetal electrocardiogram (ECG) analysis to EFM. However, large studies have shown that adding ST-segment analysis does not significantly reduce metabolic acidosis or improve overall perinatal outcomes, though it may reduce the need for certain interventions 2 4.
• Human Versus Computer Interpretation: Most EFM is interpreted visually by clinicians, but research is underway to improve accuracy with computerized systems and AI 3 7.

Electronic Fetal Monitoring Test Results & Follow-Up

Receiving and understanding EFM results is a crucial part of labor management. These findings directly inform care decisions, from ongoing monitoring to urgent interventions. However, interpreting results requires balancing the risk of missing a true problem with the risk of overreacting to false alarms.

Here is a summary of what EFM results can reveal and how providers typically respond.

What Do EFM Results Show?

• Normal Tracings: A reassuring heart rate (110–160 bpm), moderate variability, and no concerning decelerations suggest the baby is coping well with labor 3 5.
• Indeterminate Patterns: May include minimal variability, occasional decelerations, or tachycardia. These patterns warrant closer observation and sometimes further testing (such as fetal scalp blood sampling) 3 5.
• Abnormal Tracings: Recurrent late decelerations, severe bradycardia, or a flat (nonreactive) tracing can indicate serious problems such as fetal hypoxia or acidemia. Rapid decisions, including expedited delivery, may be needed 1 3 5.

The Real-World Predictive Value

While abnormal EFM findings are associated with higher rates of fetal acidemia and other complications, the predictive value is imperfect:

• Many babies with abnormal tracings are born healthy.
• Some babies with reassuring tracings still experience complications 1 3 7.
• Subjectivity and variability in interpretation contribute to both false positives (unnecessary interventions) and false negatives (missed problems) 1 7.

Follow-Up Steps and Next Actions

If EFM is Normal:

• Continue routine monitoring.
• Provide reassurance to the family.

If EFM is Indeterminate or Abnormal:

• Take steps to optimize fetal oxygenation (e.g., reposition mother, give oxygen, reduce contractions with medication).
• Consider more invasive monitoring or testing (e.g., internal EFM, fetal scalp blood sampling) 3 4 5.
• Prepare for possible expedited delivery if there is no improvement.

After Delivery:

• Babies with concerning EFM results may need additional observation or admission to a neonatal intensive care unit (NICU), especially if born with low Apgar scores or evidence of acidemia 3 4.
• Mothers may require follow-up for any interventions performed, such as cesarean delivery.

Advances in EFM Result Interpretation

Emerging technologies, including the Fetal Reserve Index and AI-based interpretation, may help clinicians better distinguish between true and false signs of distress, potentially reducing unnecessary interventions while improving safety for both mother and baby 7.

Conclusion

Electronic fetal monitoring is a central part of modern obstetric care, offering valuable real-time insights into fetal well-being during labor. However, its interpretation and effectiveness are nuanced and require careful consideration of both benefits and limitations. Here’s a recap of the main takeaways:

• EFM is primarily used to monitor fetal well-being, aiming to detect early signs of distress during labor 1 3 5.
• The technology comes in external and internal forms, recording fetal heart rate and uterine contractions 5 6.
• Findings are categorized as normal, indeterminate, or abnormal, guiding clinical decisions from continued observation to urgent intervention 3 5.
• Current research shows EFM’s predictive value for adverse outcomes is limited, and interpretation can be subjective; unnecessary interventions remain a concern 1 7.
• Emerging technologies and analytical methods may improve the accuracy and usefulness of EFM in the future 7.

By understanding both the strengths and constraints of EFM, families and healthcare providers can better navigate labor and delivery, focusing on safety, informed choices, and the best possible outcomes.