Fetal Heart Rate Decelerations: A Comprehensive Guide for Nurses

Fetal heart rate (FHR) decelerations are temporary decreases in the fetal heart rate (FHR) below the baseline, often indicating a response to uterine contractions or other factors affecting fetal oxygenation. While some decelerations are benign, others may indicate fetal distress. Nurses play a crucial role in identifying, interpreting, and responding to FHR decelerations to ensure maternal and fetal well-being.

Fetal Heart Rate Monitoring: An Overview

FHR is monitored using electronic fetal monitoring (EFM), which provides a continuous record of the FHR pattern in relation to uterine contractions. The goal is to assess fetal oxygenation and detect signs of distress.

• Normal Baseline FHR: 110–160 beats per minute (bpm).
• Categories of FHR Patterns:
  • Reassuring: Normal baseline, moderate variability, no decelerations.
  • Non-reassuring: Abnormal baseline, minimal/absent variability, or concerning decelerations.

Types of FHR Decelerations

1. Early Decelerations:

   Definition:

   Gradual decrease in FHR that mirrors uterine contractions.

   Cause:

   Head compression during contractions, stimulating the vagus nerve.

   Characteristics:

   • Onset and recovery align with the start and end of the contraction.
   • Uniform shape; rarely falls below 100 bpm.

   Clinical Significance:

   Usually benign and requires no intervention.

2. Late Decelerations:

   Definition:

   Gradual decrease in FHR with onset occurring after the peak of the contraction.

   Cause:

   Uteroplacental insufficiency leading to reduced oxygen delivery.

   Characteristics:

   • Onset after the contraction starts, with delayed recovery after the contraction ends.
   • Recurrent patterns are concerning.

   Clinical Significance:

   Associated with fetal hypoxia or acidosis; requires immediate intervention.

3. Variable Decelerations:

   Definition:

   Abrupt decrease in FHR of at least 15 bpm lasting 15 seconds to 2 minutes.

   Cause:

   Umbilical cord compression, leading to reduced blood flow and transient hypoxia.

   Characteristics:

   • Vary in shape, timing, and depth.
   • Can occur with or without contractions (sporadic or recurrent).

   Clinical Significance:

   Mild, occasional decelerations are typically benign.

   Severe, prolonged, or recurrent patterns may indicate significant cord compression or fetal compromise.

4. Prolonged Decelerations:

   Definition:

   FHR decrease of at least 15 bpm lasting more than 2 minutes but less than 10 minutes.

   Cause:

   Prolonged cord compression, maternal hypotension, or uterine tachysystole.

   Clinical Significance:

   Requires immediate evaluation and intervention to prevent fetal hypoxia.

Causes of FHR Decelerations

Maternal Causes:

• Hypotension (e.g., from epidural anesthesia).
• Uterine hyperstimulation (tachysystole).
• Position (e.g., supine hypotension).
• Dehydration or hypovolemia.

Fetal Causes:

• Head compression (early decelerations).
• Umbilical cord compression or prolapse (variable decelerations).
• Reduced oxygenation due to placental insufficiency (late decelerations).

Nursing Interventions for FHR Decelerations

1. General Interventions:

• Change maternal position (e.g., lateral or hands-and-knees) to improve uteroplacental perfusion or relieve cord compression.
• Administer supplemental oxygen to the mother (8–10 L/min via non-rebreather mask).
• Increase IV fluid rate to enhance maternal blood volume and placental perfusion.
• Stop oxytocin infusion or tocolytic agents if uterine tachysystole is present.
• Notify the provider promptly and document the interventions and outcomes.

2. Interventions by Type of Deceleration:

Early Decelerations:

• No specific intervention is needed.
• Continue to monitor for progression in labor.

Late Decelerations:

• Position the mother laterally to relieve vena cava compression.
• Administer IV fluids to correct hypotension.
• Stop uterotonic agents (e.g., oxytocin) if hyperstimulation is present.
• Prepare for expedited delivery if decelerations persist despite interventions.

Variable Decelerations:

• Reposition the mother to relieve cord compression.
• Perform an amnioinfusion (infusion of sterile fluid into the uterus) if ordered to cushion the cord.
• Monitor for signs of worsening patterns.

Prolonged Decelerations:

• Address the underlying cause (e.g., correct hypotension or reposition the mother).
• Provide oxygen and fluids to improve perfusion.
• Prepare for emergency delivery if the deceleration does not resolve promptly.

Documentation

Accurate documentation is essential:

• Type, timing, and duration of decelerations.
• Maternal and fetal responses to interventions.
• Communication with the healthcare team.
• Ongoing monitoring and reassessment.

Prevention and Education

For Patients:

• Educate on the importance of attending all prenatal visits to assess fetal health.
• Encourage hydration and optimal maternal positioning during labor.
• Provide reassurance and clear explanations during monitoring.

For Healthcare Teams:

• Regular training on FHR interpretation and emergency protocols.
• Adherence to evidence-based guidelines for labor management.

Conclusion

Fetal heart rate decelerations can range from benign to life-threatening, depending on their type and duration. Nurses are critical in detecting decelerations, implementing timely interventions, and ensuring clear communication with the healthcare team. By applying evidence-based practices, nurses can help safeguard maternal and fetal outcomes during labor and delivery.