Fetal Heart Rate Monitoring Definitions

FHR: Baseline

Mean FHR over a 10-minute period, excluding periods of large variability (> 25 bpm), rounded to closest 0 or 5

Must be identified for ≥ 2 minutes (but not necessarily 2 consecutive minutes)

FHR: Variability

Fluctuations in the baseline FHR that are irregular in amplitude and frequency (excluding accelerations and decelerations)

Fluctuations visually quantitated as the amplitude of the peak-to-trough in bpm

FHR acceleration: Gestational age-appropriate

Visually apparent abrupt increase in the FHR < 32 weeks: Peak ≥ 10 beats/minute > baseline FHR for ≥ 10 seconds

≥ 32 weeks EGA: Peak ≥ 15 beats/minute > baseline FHR for ≥ 15 seconds

FHR deceleration: Relation to uterine contractions

Late: Temporary, gradual decrease in FHR that begins after the peak of a uterine contraction and takes ≥ 30 seconds to reach its nadir, which occurs after peak of contraction

Onset, peak, and end of deceleration usually later than the onset, peak, and end of contraction

Early: Temporary, gradual decrease in FHR that begins near the start of a uterine contraction and takes ≥ 30 seconds to reach its nadir, which occurs near peak of uterine contraction

Onset, peak, and end of deceleration usually near the onset, peak, and end of contraction

Variable: Temporary, abrupt decrease of ≥ 15 beats/minute in FHR that reaches its nadir < 30 seconds after deceleration begins and lasts between 15 seconds and 2 minutes; decelerations that may or may not be associated with uterine contractions

Onset, depth, and duration commonly varying between successive uterine contractions