What are early, variable and late decelerations, and what does each suggest?

• Early decelerations - mirror the contraction (onset and nadir with the peak); due to head compression; benign
• Variable decelerations - vary in shape/timing, abrupt drop; due to cord compression; commonest in labour, usually benign unless 'complicated'
• Late decelerations - U-shaped, onset after the contraction peak with delayed recovery; due to uteroplacental insufficiency; concerning (hypoxia)

Clinical relevance. Distinguishing deceleration types (head vs cord vs placental) determines the level of concern and action.

More Detail

Types of deceleration

The timing and shape of decelerations relative to contractions point to the cause and significance.

Early decelerations

• Mirror the contraction - onset, nadir and recovery coincide with the contraction.
• Due to fetal head compression (vagal response); benign.

Variable decelerations

• Vary in shape, size and timing, with an abrupt drop and recovery.
• Due to umbilical cord compression; the commonest type in labour and usually benign.
• Become non-reassuring ('complicated') with concerning features - loss of the 'shouldering', slow recovery, lasting >60 s or dropping >60 bpm, reduced variability within the deceleration.

Late decelerations

• U-shaped, with onset after the contraction peak and delayed recovery, often with reduced variability.
• Due to uteroplacental insufficiency and fetal hypoxia; concerning.

Prolonged deceleration

A deceleration lasting more than 3 minutes (especially <80 bpm with reduced variability) is an acute event requiring urgent action.