The os now begins to stretch and widen, the bag of waters becomes more and more evident, vomiting occurs, and at last, when the os has expanded to a diameter of four inches (ten centimeters), the membrane can withstand the pressure no longer. It ruptures, a certain amount of fluid escapes, the presenting part comes down against the opening, and like a valve, prevents the outflow of the waters from above.
Fig. 36.—The effect of the pains. The cervix before labor begins. (Bumm.)
Fig. 37.—The effect of the pains. The cervix begins to be “effaced.” (Bumm.)
Fig. 38.—The effect of the pains. The cervix is effaced, and the dilatation of the os begins. (Bumm.)
Fig. 39.—The effect of the pains. The cervix is effaced, and the os continues to dilate. (Bumm.)
Sometimes the labor may be preceded by some hours (two or three), or days (two or three), even weeks (two or three), by the rupture of the membrane, and sometimes when the structure is thick and tough, the rupture may be delayed until well into the second stage, or even until the child is born. In the latter case, the head comes out, covered with membrane. In the old days, this was called being “born with a caul.” It was supposed to be a lucky omen, but it was lucky only that the babe escaped suffocation. The membrane should be torn open quickly.