Fetal Monitoring Variability and Heart Rate Patterns

Fetal Monitoring Variability

• Absent Variability: Amplitude range undetectable. Associated with fetal hypoxemia, metabolic acidemia, congenital anomalies, or preexisting neurologic injury.
• Minimal Variability: Amplitude range detectable ≤5 bpm. Causes include fetal hypoxemia, CNS depressant medications, and can occur during sleep states.
• Moderate Variability: Amplitude range 6-25 bpm. Indicates normal fetal acid-base balance and normal FHR regulation unaffected by sleep cycles or conditions.
• Marked Variability: Amplitude range ≥25 bpm. May signify fetal distress and should be monitored closely.

Fetal Heart Rate Patterns

• Sinusoidal Pattern: Smooth, wavelike undulating pattern lasting 3-5 minutes, persisting for at least 20 minutes; may indicate chorioamnionitis or fetal sepsis.
• Fetal Tachycardia: FHR >160 bpm for more than 10 minutes. Causes include hypoxemia, maternal fever, infections, and certain medications; clinical significance varies based on associated conditions and interventions needed.
• Fetal Bradycardia: FHR <110 bpm for >10 minutes. Possible causes include heart block, structural defects, and maternal conditions. Significance depends on underlying cause and accompanying patterns.

Accelerations and Decelerations

• Accelerations: Apparent increases in FHR above baseline; sign of fetal well-being. Caused by movements, examinations, or contractions.
• Early Decelerations: Gradual decrease in FHR coinciding with contractions. Generally normal, caused by head compression.
• Late Decelerations: Decrease in FHR occurring after contractions. Indicative of possible fetal hypoxemia or uteroplacental insufficiency; requires immediate intervention.
• Variable Decelerations: Abrupt FHR decrease due to umbilical cord compression; generally transient and correctable through maternal position changes.
• Prolonged Decelerations: Decrease lasting >2 minutes but <10 minutes; indicates prolonged interruption in fetal oxygen supply.

Clinical Significance and Interventions

• For Late Decelerations involving uteroplacental insufficiency, interventions may include changing maternal position, increasing IV fluid rates, or administering oxygen.
• Variable Decelerations may require maternal repositioning or potential amnioinfusion if indicated.
• Bradycardia and Tachycardia interventions depend on the cause, e.g., treating maternal hypotension for bradycardia or antipyretic administration for tachycardia.

Baseline Heart Rates and Reassuring Patterns

• Normal baseline FHR ranges from 110-160 bpm. The presence of moderate variability and accelerations is generally reassuring.
• Any tracing with absent variability or concerning decelerations (late or prolonged) necessitates further evaluation and intervention.

Summary of FHT Findings

• Details such as baseline, variability, presence of accelerations, decelerations, and contractions are critical for assessing the fetal heart tracing.
• Regular monitoring and prompt intervention for nonreassuring patterns are essential for maternal-fetal health.