The relationship between progesterone, uterine volume, intrauterine pressure, and clinical progress in hypertonic saline—induced abortions

Abstract

During hypertonic saline—induced abortions, intrauterine pressure (IUP) and plasma progesterone (P) have been measured and the uterine volume (V) estimated in 13 patients. During the initial third of the instillation-abortion time, the decrease in P was proportionately greater than the increase in IUP, indicating that P withdrawal precedes the evolution of IUP and clinical progress. In 2 additional patients, with low P levels, the evolution of IUP and abortion have been induced by a mere increase in V, using isotonic (rather than hypertonic) saline. In these 2 patients P withdrawal only manifested when the evolution of IUP approached completion. Since the changes in P did not account fully for the changes in IUP, the ratio V/P was calculated at various phases of hypertonic saline—induced abortion. It then became apparent that whenever V increases or P decreases markedly, without compensatory changes in P or V, the IUP evolves and pregnancy terminates. It is concluded that current concepts in myometrial regulation may be advanced by quantitating V and P in individual patients whose IUP is measured.