|Preventing Prolonged Labour I (WHO - OMS, 1994, 22 p.)|
E.A. Friedman in 1954, following a study on a large number of women in the USA, described a normal cervical dilatation pattern (see Fig. I.1) (24).
Fig. 1.1. Friedmans curve showing phase of maximum slope
Friedman divided labour functionally into two parts. The (early) latent phase extends over 8-10 hours and up to about 3 cm dilation. This was followed by an active phase, characterized by acceleration from about 3-10 cm at the end of which deceleration occurred. This work has been the foundation on which others have built.
In 1969 Hendricks et al. demonstrated that, in the active phase of normal labour, the rate of dilatation of the cervix in primigravidae and multiparae varies little and that there is no deceleration phase at the end of the first stage of labour (25).
Philpott, in extensive studies of primigravidae in Central and Southern Africa, constructed a nomogram for cervical dilatation in his population and was able to identify deviations from the normal and provide a sound scientific basis for early intervention leading to the prevention of prolonged labour (11). Since then, various authors have developed similar nomograms in other geographical areas. None of these have shown significant differences between ethnic groups (14, 26, 27, 28, 29, 30, 31, 32).