ABSTRACT
Fetal distress is a frequent reason for obstetric intervention during labour. The final diagnosis generally is based upon the information in the cardiotocographic tracings, whether or not combined with the information from fetal scalp blood sampling. Reading, classification and interpretation of fetal heart rate (FHR) recordings is subject to considerable interobserver variation, even among experienced obstetricians. Far too often, individual decelerations in the heart rate are classified as early or late, merely on the basis of the relationship between the decelerations and the accompanying contraction. Hon's original flow sheet for classification of decelerations dictates assessment of the full tracing with, as a primary step: are decelerations uniform or not? Non-uniform decelerations should automatically be classified as variable. Comparison between the onset of the deceleration and the uterine contraction curve is the second step. Variable decelerations are the predominant type in the majority of intrapartum recordings. Features in the FHR rhythm to be assessed in case of variable decelerations include assessment of the baseline level, presence or absence of accelerations, variability in the baseline pattern and during the decelerative part of the tracing, initial and secondary acceleration, overshoot following the deceleration whether or not with smoothing, recovery from the deceleration, continuation of the baseline level and the time intervals between contractions or recurrent efforts of pushing activity. The paper further addresses pathophysiologic mechanisms of fetal distress, maternal and fetal risk factors and various alternatives in the management of intrapartum distress.
