Fetal Heart Rate and Contraction Patterns
Key Points
- Normal fetal heart rate baseline is 110 to 160 bpm measured over a 10-minute segment.
- Moderate variability (6 to 25 bpm) is the most reassuring variability pattern.
- Deceleration type and timing guide urgency: early is usually benign, while late, repetitive variable, and prolonged patterns increase hypoxia concern.
Pathophysiology
Fetal heart rate (FHR) reflects dynamic autonomic regulation and oxygenation status during labor. Sympathetic input tends to increase FHR, while parasympathetic input decreases it; changes in oxygenation and acid-base status alter this balance and produce recognizable tracing patterns.
Uterine contractions can transiently affect placental and cord blood flow. Pattern interpretation therefore relies on integrating baseline rate, variability quality, periodic accelerations/decelerations, and contraction context rather than any single tracing feature.
Classification
- Baseline: Average FHR in 10 minutes, excluding major periodic changes.
- Variability: Absent, minimal, moderate, or marked beat-to-beat fluctuation.
- Periodic increases: Accelerations (usually reassuring).
- Periodic decreases: Early, late, variable, or prolonged decelerations.
- Contraction pattern: Frequency, duration, and intensity trend over time.
Nursing Assessment
NCLEX Focus
Priority assessment asks whether current tracing suggests reassuring adaptation or evolving fetal hypoxia that needs immediate intrauterine resuscitation.
- Determine baseline and identify tachycardia (>160 for 10 minutes) or bradycardia (<110 for 10 minutes).
- Classify variability, emphasizing loss of moderate variability as a key warning trend.
- Differentiate deceleration type by onset, shape, relation to contractions, and recovery timing.
- Evaluate contraction frequency/duration/intensity and identify patterns that worsen fetal tolerance.
Nursing Interventions
- Reposition laboring patient, initiate IV fluid bolus when indicated, and escalate nonreassuring changes to provider promptly.
- For concerning bradycardia or deceleration patterns, implement unit intrauterine resuscitation sequence and continuous reassessment.
- Communicate pattern evolution clearly using standardized terminology to support team decisions.
Hypoxia Escalation
Persistent late decelerations, prolonged decelerations, or progressive variability loss can indicate worsening fetal oxygen compromise and require urgent action.
Pharmacology
| Drug Class | Examples | Key Nursing Considerations |
|---|---|---|
| tocolytics | Terbutaline use context | May be used when tachysystole contributes to fetal bradycardia; verify maternal pulse before administration. |
| labor-analgesics | Epidural and other options | Interpret tracing changes with medication effects and maternal status in mind. |
Clinical Judgment Application
Clinical Scenario
A laboring patient develops repetitive variable decelerations followed by a prolonged deceleration after frequent contractions.
Recognize Cues: Abrupt recurrent decelerations, prolonged nadir, and contraction stress pattern. Analyze Cues: Umbilical cord compression with possible emerging fetal hypoxia. Prioritize Hypotheses: Immediate fetal oxygenation risk is highest priority. Generate Solutions: Reposition, fluid support, evaluate contraction burden, and notify provider urgently. Take Action: Start intrauterine resuscitation measures and maintain close tracing surveillance. Evaluate Outcomes: Baseline/variability improve and decelerations decrease in frequency or severity.
Related Concepts
- external-and-internal-fetal-monitoring - Monitoring method affects signal reliability and response speed.
- intrauterine-resuscitation - Escalation bundle for nonreassuring fetal status.
- stages-of-labor - Stage context informs expected tracing and contraction dynamics.
- physiologic-adaptations-during-labor-and-birth - Maternal adaptations influence fetal tracing interpretation.
- umbilical-cord-compression - Core mechanism behind many variable deceleration patterns.
Self-Check
- Which FHR variability category is most reassuring and why?
- How do late decelerations differ from early decelerations in clinical significance?
- Which first nursing actions are prioritized for prolonged fetal bradycardia?