FHR Late Decelerations
Overview
Late decelerations are symmetric, gradual drops in fetal heart rate that begin AFTER the peak of a contraction and return to baseline AFTER the contraction ends — the nadir lags the contraction acme. This timing offset reflects uteroplacental insufficiency: the placenta cannot deliver adequate oxygen during the stress of the contraction, so the fetal response is delayed. A single late decel signals reduced placental reserve; a repetitive pattern (≥50% of contractions over 20 minutes) is never benign.
Mechanism of a late deceleration
- Uteroplacental insufficiencyplacenta cannot meet oxygen demand during contraction
- Reduced fetal oxygenationdelayed hypoxic response
- Late decelerationgradual, symmetric U; nadir AFTER contraction peak
- Recovery after contraction endsdecel resolves late, not with the contraction
Interpretation
Late vs early vs variable decelerations
Late
- Onset
- Gradual (≥30 s to nadir)
- Nadir timing
- After contraction peak
- Mechanism
- Uteroplacental insufficiency
- Concern
- Always concerning
Early
- Onset
- Gradual
- Nadir timing
- At contraction peak
- Mechanism
- Fetal head compression
- Concern
- Benign
Variable
- Onset
- Abrupt
- Nadir timing
- Variable, unrelated
- Mechanism
- Umbilical cord compression
- Concern
- Depends; relieve cord
During — Monitoring
Monitor
Technique
Intrauterine resuscitation for recurrent late decelerations — act in this sequence (mnemonic STOP: Side-lying, Turn off oxytocin, Oxygen on, Push fluids). Stopping oxytocin is an independent nursing action that needs no provider order during a nonreassuring tracing.
Patient Teaching
Clinical Pearl
Late to the party, late to leave: the decel starts, bottoms out, and recovers AFTER the contraction — that delay means the placenta, not the cord. First response is STOP: Side-lying, Turn off oxytocin, Oxygen on, Push fluids.