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Quantitative labor data have been reported piecemeal in the literature; there is no previous unified report of the frequencies of each of the dysfunctional labor patterns (DLPs). In order to describe the labor process more clearly a labor diagnostic computer program was used to prospectively study an unselected series of 3,682 nearly consecutive labors from one institution. Cervicometric data for nulliparous and multiparous labor were very similar to the results of others. The absolute frequency with which each DLP was found to occur is compared with results in the literature. Protracted active phase dilatation was the most frequently occurring DLP and prolonged deceleration phase the least frequently occurring one. The relative frequencies of the DLPs, defined as the percentage of all DLPs that occurred, remained reasonably constant, regardless of parity or the absolute frequencies of the DLPs in a group of patients.

The mechanical properties of the chorioamniotic membranes have been studied by several investigators over the past 100 years. No relationship between membrane strength, as measured by rupture tension, and premature or non-premature rupture of the membranes has been demonstrable. In the present study, several measures of the mechanical properties of the chorioamniotic membranes were examined. These included thickness, rupture tension, work to rupture, strain to rupture, and moduli of elasticity (Young). Prematurely and non-prematurely ruptured membranes differed with respect to thickness near the rupture site and Young's modulus near the placenta. Differences between the groups for the other parameters were not significant. This study suggests that there may be inherent differences between membranes which rupture prematurely and those which do not.