by George Malcolm Morley, MB ChB FACOG
Figure 2 - Umbilical/placental venous pressure
recorded in mms. of Hg. with a catheter inserted in the vein after cutting and
clamping the cord 45 seconds after delivery. The first contraction is about one
minute post partum (1) as the uterus closes round the placenta. Successive
contractions (2 & 3) generate pressures of over 100 mms. of Hg. until the
placenta is separated during contraction (4). A fifth contraction pushes the
placenta through the lower segment into the vagina (5) followed by sharp peaks
of pressure due to maternal effort which eventually expels the placenta from the
vulva (6). This third stage of labor followed a spontaneous term labor and
delivery. No medication was used.
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