Table 3.
Summary of the 2015 FIGO intrapartum cardiotocography (CTG) classification system.47
| Normal CTGa | Suspicious CTG | Pathological CTG | |
|---|---|---|---|
| Baselineb | 110–160 bpm | Lacking at least one of normal characteristics, but with no pathological features | <100bpm |
| Variabilityc,d,j | 5–25 bpm | Reduced/increased variabilityc,d; sinusoidal patternj | |
| Decelerationse,f,g,h,i | No repetitive* decelerations | Repetitive* late or prolonged decelerations for >30 min (or >20 min if reduced variability); one deceleration >5 min | |
| Interpretation | No hypoxia/acidosis | Low probability of hypoxia/acidosis | High probability of hypoxia/acidosis |
Decelerations are repetitive if they occur at >50% of uterine contractions.
Accelerations (amplitude >15 bpm, lasting >15 s but <10 min) are not included in the intrapartum CTG classification system because their absence have uncertain significance, but presence of accelerations indicates a neurologically responsive fetus without hypoxia/acidosis.
Tachycardia defined as >160 bpm for >10 min, bradycardia defined as <110 bpm for >10 min. A baseline 100–110 bpm may occur in normal fetuses, especially if postdate.
Reduced variability is bandwidth <5 bpm for >50 min in baseline segments, or for >3 min during decelerations.
Increased variability (saltatory pattern) is bandwidth >25 bpm for >30 min.
A deceleration is a loss of heart rate of >15 bpm for >15 s.
Early decelerations are shallow, short-lasting, have normal variability, and are coincident with uterine contractions.
Variable decelerations have a rapid drop to nadir within 30 s after onset, good variability, rapid return to baseline, are V-shaped but vary in shape, size and relation to uterine contractions.
Late decelerations are U-shaped with reduced variability, start more than 20 s after the onset of uterine contraction with a gradual onset with >30 s to nadir, have a nadir after the acme of contraction, and return to baseline gradually with >30 s from nadir to baseline.
Prolonged decelerations are lasting >3 min. Decelerations remaining <80 bpm for >5 min and with reduced variability are serious.
Sinusoidal pattern is a regular, smooth, undulating pattern resembling a sinus wave, with amplitude 5–15 bpm at frequency 3–5 cycles/min, lasting for >30 min and coinciding with absent accelerations.