Revising the primigravid partogram: does it make any difference?

To investigate the distribution of the rate of cervical dilatation of primigravid labour and its deviation from the standard partogram. Retrospective observational study. South African district hospital serving an indigent rural population. Expectant management of labour of healthy nulliparous women in active labour, at term, with a singleton pregnancy and cephalic presentation. Audit of 1,595 partograms of spontaneous primigravid labour. The standard partogram's alert line was replaced by a customised alert line based on the lowest 10th centile of the rate of cervical dilatation of the study population and an alert line representing the 10% slowest labours. The action line was placed parallel and 4 h to the right of the alert lines. The distribution of labours left to and on the respective alert lines, and right to the action lines. The lowest 90th centile of the customised alert line yielded a rate of cervical dilatation of 0.860 cm/h. Three quarters of labours evolved left to the revised alert line as opposed to 56.1% left of the standard alert line [Odds ratio (OR) 0.49, 95% confidence interval (CI) 0.42-0.56]. The mean rate of cervical dilatation of the 10% slowest labours was 0.535 +/- A 0.076 cm/h (P < 0.0001), and 95.7% of labours evolved left to the corresponding alert line (OR 8.40, 95% CI 6.44-11.0). The alert line representing the mean of the 10% slowest labours leads to an unrealistic distribution of labour on the partogram. A revised alert line based on the lowest 10th centile of the local population is more representative and should perhaps be used in the management of labour.