An increase of 15 BPM above baseline for 15 seconds twice in a 20 minute period. Since the amplitude of accelerations is inversely proportional to the rate premature fetuses often do not meet criteria for reactivity. Fetal scalp stimulation can be used to induce accelerations. Episodic patterns are those not associated with uterine contractions . Periodic patterns are those associated with uterine contractions.
Variables can also be periodic.
Quantitated by the depth of the nadir in BPM below the baseline. The duration is quantitated in minutes and seconds from the beginning to the end of the deceleration. The type of the deceleration is distinguished on the basis of its waveform. Further subclassified based on their relation to the contraction. Decrease lasts for 2 to 10 minutes.