What cervical dilatation rate during active labour should be considered abnormal?

The present study tested the common notion of slow labour that only dilatation rates of 1 cm/h and above lead to normal (intervention free) delivery. We examined all primiparous spontaneous term labours cared for in our hospital over a 1 year period when a protocol for intervention in the case of slow dilation rate was not in place. Of 505 consecutive singleton labours, 105 (20.6%) progressed at an overall cervical dilatation rate of less than 1 cm/h. However, only those progressing at 0.5 cm/h and less (n = 52 or 10.3% of the total) had significantly increased rates of oxytocin usage and of caesarean section. The data suggest that there may be a more conservative definition of slow labour.