- 1.1. External tokodynamometric recordings with special reference to the lower uterine segment were made in an unselected consecutive series of 25 patients who were 38 weeks pregnant, 23 of whom had borne one to three children. Labor was initiated by artificial rupture of the membranes. Recordings were started before labor and continued throughout the first stage and into the early second stage, to study the pattern of contractility before and during full development of the lower uterine segment.
- 2.2. The patterns recorded included: (I) lower segment activity during effacement; (IIA) transition from lower uterine activity during effacement to apparent inactivity with full effacement, shown in a majority of the grop; (IIB) continued lower uterine segment activity after effacement, shown in a minority; (III) reappearance of lower segment activity in the late first stage in 12 patients; (IV) dominance of lower segment activity over fundal activity for a period of twenty minutes to three hours without appreciable change in the character of labor. This was in a small group.
- 3.3. It is postulated that these changes reflect myometrial redistribution in labor during the formation of the lower uterine segment and that this factor should be taken into consideration in the interpretation of uterine physiology as recorded by external tokodynamometer.
- 4.4. Continued activity of the lower uterine segment after full effacement may be an important etiological cause for rupture of the lower uterine segment during labor in both the intact uterus and the uterus after previous cesarean section.
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- Clinical Measurement of Uterine Forces in Pregnancy and Labor. Charles C Thomas, Publisher, Springfield, Ill1954: 65
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☆Project supported by a grant from The Schering Corporation, Bloomfield, N. J., and by the Division of Grants, National Institutes of Health, United States Public Health Service.