Journal of Applied Physiology, Vol 38, Issue 3 443-448, Copyright © 1975 by American Physiological Society
Intrauterine pressure wave-form characteristics of spontaneous first stage labor
J. Seitchik and M. L. Chatkoff
Intrauterine pressure wave-form parameters were measured in 827
contractions obtained from 26 patients in spontaneous labor. The
coefficients of correlation between the maximal and minimal rates of
pressure change and the maximal pressure amplitude were 0.78 and 0.63,
respectively, and greater than or equal to 0.70 in 22/26 patients.
Contractions partitioned into decile statistical groups of the pressure
amplitude and both maximal and minimal rates. A linear relationship between
these parameters has therefore been established. Contractions of greater
amplitude tend to be longer, but the relationship between duration and
amplitude is nonlinear with a limiting maximum contraction time. The
duration of the midportion of the pressure wave appears invariate with
respect to wave amplitude and only start-up and termination times increase
with increasing amplitude. Mean values and standard deviations of the
maximal amplitude (40.4 +/- 16.9mmHg). the maximal (2.4 +/- 0.9 mmHg/s) and
minimal (-2.1+/- 0.9 mmHg/s)rates of pressure change, and the total
duration of contractions (68.6 +/- 17.8s) were determined.
