Overview
This lecture covers the essentials of fetal heart rate monitoring, focusing on interpretation of tracings, types of decelerations, key interventions, and critical values for safe maternal and fetal outcomes.
Basics of Fetal Heart Rate Monitoring
- Fetal heart rate monitoring assesses fetal well-being and oxygenation during labor.
- Two external monitors: ultrasound (sono) for fetal heart rate and toco for uterine contractions.
- Sensor placement depends on fetal position; PMI (point of maximal impulse) is key.
- Internal monitoring (fetal scalp electrode, FSE) is more accurate but invasive, used only after membrane rupture and ≥2 cm dilatation, and carries infection risk.
Terminology and Normal Findings
- Normal fetal heart rate: 110–160 beats per minute (bpm).
- Variability: the "wiggle" in heart rate; moderate variability indicates fetal well-being.
- Accelerations: temporary HR increases, indicating good oxygenation; these are reassuring.
- Early decelerations: shallow dips mirroring contractions, caused by head compression, and are normal.
Abnormal Patterns and Critical Interventions
- Minimal variability: flat line, may mean fetal sleep or distress—monitor closely.
- Absent variability: no movement, emergency; prepare for C-section.
- Tachycardia: FHR >160 bpm for >10 min; early distress, often due to maternal fever, infection, or stimulant use.
- Bradycardia: FHR <110 bpm for >10 min; caused by uteroplacental insufficiency, cord prolapse, maternal hypotension, or analgesics.
- Variable decelerations: deep, abrupt V-shaped dips; caused by cord compression—reposition mom, provide O2, stop oxytocin, increase IV fluids, consider amnioinfusion.
- Late decelerations: HR drops after contractions; due to placental insufficiency—stop oxytocin, reposition, provide O2, IV fluids, notify HCP, prepare for C-section if unresolved.
- Sinusoidal pattern: wavelike HR, no variability or response; most deadly, requires immediate C-section.
Uterine Contractions
- Frequency: time from start of one contraction to start of next (measured in minutes).
- Duration: length of contraction (measured in seconds).
- Intensity: strength, palpated externally or measured in mmHg internally.
- Rest: uterus should relax at least 60 seconds between contractions to allow fetal recovery.
Key Terms & Definitions
- PMI (Point of Maximal Impulse) — Optimal site to place FHR monitor, located between fetal shoulder blades.
- FSE (Fetal Scalp Electrode) — Internal electrode for direct fetal HR measurement.
- Variability — Fluctuations in FHR baseline, reflects neuro status.
- Accelerations — Temporary HR rises, sign of fetal well-being.
- Decelerations — Decreases in FHR; types: early (head compression, normal), variable (cord compression), late (placental insufficiency, dangerous).
- Sinusoidal pattern — Smooth, wave-like baseline with no variability; signals severe fetal compromise.
Action Items / Next Steps
- Memorize normal FHR range (110–160 bpm) and key abnormal patterns.
- Learn and practice “ROADI” interventions for nonreassuring tracings.
- Review sample tracings and practice interpretation.
- Be prepared to identify intervention priorities in exam questions.