Development of gradual hypoxia owing to the intermittent contractions of labour cause: 1) absence of accelerations; 2) gradual increase in the baseline rate; and 3) reduction in baseline variability. Decelerations present in the trace may indicate the mechanism which is causing the hypoxia. Acute hypoxia owing to cord prolapse, abruption, scar dehiscence or severe hypertonic contraction caused by oxytocin, may present with prolonged bradycardia. These acute events have to be anticipated and detected by clinical means. Certain features associated with decelerations will indicate a greater possibility of developing hypoxia. These are repeated late decelerations, variable decelerations with features of late recovery, reduced baseline variability during and between decelerations, or a deceleration depth >60 beats with duration >60 s. When interpreting a trace all the features of the trace have to be considered in order to classify it as normal, suspicious or abnormal. Debate as to whether decelerations are variable or late may lead to disagreement. Action has to be based on the clinical picture and the trace. A given trace may need no action in the late first stage but intervention in the form of fetal blood sampling or delivery may be warranted in the early first stage of labour.
|Number of pages||7|
|Journal||Current Obstetrics and Gynaecology|
|Publication status||Published - 1996|