DISCUSSION

n this study the curve of normal cervical dilatation begins at zero time as the time of admission in labour. It would be possible to apply the slope of the mean acceleration phase of a number of normal labours studied, to show the expected progress of labour from a dilatation of 3 cm. The start of observation of labour, however is not at some defined time corresponding with the onset of the acceleration , but it is at zero time when the patient is first examined in labour. Women present in labour at different cervical dilatations and for those presenting at dilatation more than 3 cm. It would be inappropriate to use nomograms used for women with 3 cm dilatation at admission. Such use would lead to an error in making a decision about the time of intervention leading to undue morbidity to mother and foetus.

The eight separate patterns representing normal labour progression are compiled from groups of patients admitted at eight different cervical dilatations. The composite date can be etched onto a stencil for use in conjunction with the graphic records. The mean rate of cervical dilatation per hour is 1.014 cm per hour with a standard deviation of +/- 0.086 cm per hour. The variations from normal are statistically insignificant in the graphs from 3 cm to 8 cm. The 2 cm graph has a significant no. of variations whereas the 9 cm graph has no variations. The 2 cm graph is not truly representative of cervicographic progress because this part falls in latent phase of labour, the duration of which is normally variable.

The nomograms constructed allow a greater understanding of labour and help to identify the "at risk" group of patients with dysfunctional labour. Once the graph strays 2 hrs to the right of the nomogram then labour requires revaluation. All parameters are checked. The foetal heart rate is monitored closely. A complete pelvimetry and assessment of uterine activity is done.Cephalo-pelvic disproportion or any malposition of the foetus or deflexion of the head is ruled out and then accordingly either intervention or augmentation with oxytocins or prostaglandins after amniotomy is done, according to the suitability to that particular case. Prolonged labour which leads to infection, foetal asphyxia, obstructed labour and the operative and anaesthetic hazards of delayed intervention is avoided due to earlier detection and thus selection of patients who really require augmentation of labour is done.

There is greater propensity for dysfunctional labour to occur among primigravidas and hence it is essential to define the patterns of abnormal labour. The curve of normal cervical dilatations described by Friedman is not appropriate for early recognition of patients in prolonged labour because Friedman's curves begin at the so called onset of labour at zero cms and the latent phase is of variable duration. The factors prevent accurate placing of the first assessment of cervical dilatation along the graph. These problems are overcome by referring the admission dilatation to the nomograms of cervical dilatation constructed in the study.

Philpott's graphic records show that the two factors which have a major influence on the length of labour and mode of delivery are the patients cervimetric progress and the presence or absence of a lumbar epidural block. Philpott and Castle reported in African primigravidae, a decrease in cesarean section rate from 9.9% in 1966 to 2.6% in 1972 after the establishment of "alert and action" lines. These lines need modification as, a women who is admitted at a cervical dilatation of 5 cms or more, who subsequently develops secondary arrest will wait too long before reaching the action line.

Studd has constructed nomograms based on analysis of 176 caucasian nulliparous women whereas this study has analysed 800 normal labours. Also, Studd has shown women with cervimetric progress at dilatation of 0 to 2, 3 to 4, 5 to 6, 7 to 8 and 9 to 10, thus five slopes normal labour admitted at five different values of cervical dilatations drawn. The present study shows nomograms for each cm of cervical dilatation starting form 2 cm to 9 cm so that the appropriate stencil is used to draw the relevant pencil line of expected progress on the patients cervicograph. Error due to drawing a single line for a range of cervical dilatations at admissions is eliminated.

Multiparous patients can also be monitored by using these nomograms as primigravidae have slower progress than multiparas and so dysfunctional labour can be detected easily. Going by the faster cervical dilatation rate in multiparas, intervention by standard nomograms would be delayed. Therefore separate nomograms should be drawn for normal multigravidas in labour by another study based on similar principles.

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