Table 3 FHR parameters and their definition (modified after ACOG, FIGO, SOGC, RCOG).

Term	Definition
* Recent studies found that the physiological range for fetal heart rate at term was probably between 115 (4th percentile) and 160 beats per minute (96th percentile) (17, 105; EL II).** < 32nd week of gestation, rise of FHR > 10 bpm or > ½ range and > 10 seconds. If accelerations are > 10 minutes, this is considered a change in the baseline rate.
Baseline (bpm)	is mean FHR maintained over at least 10 minutes in the absence of accelerations or decelerations, given in beats per minute (bpm). For immature fetuses, mean FHR was in the upper range of variation. A progressive increase of FHR must be monitored carefully!
normal	normal range: 110–160 bpm*
suspicious	slight bradycardia: 100–109 bpm
	slight tachycardia: 161–180 bpm without simultaneous accelerations
pathological	severe bradycardia: < 100 bpm
	severe tachycardia: > 180 bpm
Range (variability) (bpm)	fluctuations in the fetal baseline rate occur 3–5 times per minute. The range is the difference in bpm between the highest and the lowest fluctuation during the most part of the 30 minute reading monitor strip.
normal	> 5 bpm during the interval when no contractions occur
suspicious	< 5 bpm and > 40 minutes, but < 90 minutes or > 25 bpm
pathological	< 5 bpm and > 90 minutes
Accelerations	increase of FHR > 15 bpm or > ½ range and > 15 seconds**
normal	two accelerations in 20 minutes
suspicious	periodical occurrence with every contraction
pathological	no accelerations > 40 minutes (significance is still unclear, assessment is therefore questionable)
Decelerations	drop in FHR > 15 bpm or > ½ range and > 15 seconds
normal	none
suspicious	early: uniform, periodically recurring drop in FHR is correlated with contractions, decrease in FHR begins at the start of contraction. Return to baseline at the end of the contraction. Variable decelerations: variations in form, duration, depth and correlation with contractions, intermittent/periodically recurring decrease in FHR with rapid onset and quick recovery. Can also appear as an isolated phenomenon (associated with fetal movements). Prolonged decelerations: abrupt FHR drop below baseline for at least 60–90 seconds < 3 minutes.
pathological	Late: uniform, periodically recurring FHR decrease is correlated with contractions and starts between the middle and end of the contraction. Nadir > 20 seconds after contraction has peaked. Return to baseline after contraction has ended.If the range is < 5 bpm, decelerations < 15 bpm may also be pathological.
	Atypical variable: decelerations with one of the following additional characteristics: loss of primary or secondary FHR rise, slow return to baseline after the contraction has ended, longer increased baseline after contraction, biphasic deceleration, loss of oscillation during deceleration, resumption of baseline rate at a lower level.
	Prolonged decelerations: must be considered pathological if they persist for more than two contractions or > 3 minutes.
	Sinusoidal pattern: long-term fluctuation of baseline resembling a sinus waveform. The smooth undulating pattern lasts at least 10 minutes and returns at relatively fixed intervals of 3–5 cycles per minute with an amplitude of 5–15 bpm above and below baseline. No variability of baseline can be established.