Generally, when the cervix has dilated to a certain variable extent, the bag of waters, being only imperfectly supported by the cervix, and no longer having sufficient strength to resist the pressure made upon it by the amniotic fluid, under the influence of uterine contraction, yields to the pressure, and the liquor amnii escapes. But, often, this rupture is retarded by two very different causes. In one case the membranes, very tough and thick, resist on this account. In the other case, although apparently thinner and weaker, they seem to possess a peculiar elasticity which causes them to grow thinner as they are distended. In some ex ceptional cases one sees the membranes propelled to the vulva, in front of the head, at the moment of its liberation. The infant is, thus, born " with a caul," formed by a part of the membranes, which are torn at the moment of the expulsion of the head. At other times the membranes do not rupture, and the ovum is expelled entire. Although certain authors have reported cases in which the ovum escaped in this way at term, we consider them very exceptional, and we find, on consulting the records of the clinique, where five or six analogous cases are reported, that the foetuses were from five to seven months old, and that some of them had been dead for a certain time. Although delayed rupture of the membranes is rare, it is very common to see cases of premature laceration, so that the time of the rupture is variable. Ordinarily, this rupture coincides with the first expulsive pains, but it is not rare to see it occur from twelve to twenty-four hours before labor begins. Some rare cases, in which labor was delayed much longer, after the rupture, have been reported. Rainy and Garipuy have seen an interval of thirteen days, and another of thirteen and one half days, between the rupture and the beginning of parturition. The interval in one of our own cases was twelve days and in another fourteen days. Chantreuil's two cases had intervals of twelve and twenty-seven days, respectively. Campbell cites an interval of seventeen days. We have recently seen a case in which the interval was forty-four days. The most exceptional cases are those of Poullet, in which the expulsion of the living foetus took place, in one instance six weeks, and, in another, five weeks after rupture of the mem branes. We are inclined to consider these cases examples of hydror Hues, rather than of premature rupture of the membranes. Generally of little importance, the premature rupture of the membranes may, if the child be dead, have much more serious results. Allowing the air to reach the cavity of the uterus, rupture favors putrefaction of the foetus, and, provided that expulsion be delayed, the development of putrid gases in the uterus, as a result of changes in the foetus, becomes a source of great danger to the mother. We saw one such case when assisting at the clinique. The patient died of putrid infection.
Ribemont has proved that rupture may occur in two ways: The mem branes rupture simultaneously, or the decidna and the chorion yield first and the amnion afterward. Hence the different forms of rupture. The accompanying figure, borrowed from him, shows these different varieties.
Generally, when spontaneous rupture of the membranes occurs, labor is accelerated from that moment, and Churchill has noted that, out of 812 cases, labor occurred in 658 cases within four hours after the rupture, and, in the other 154 cases, the time varied between 6 and 150 hours. There is a great difference, in this particular, between primiparie and multi pane. In primiparie, the average interval between rupture of the mem brane and labor is from two to four hours, but it is not so in multiparte. In the latter the usual interval is one to two hours, but labor often occurs in half an hour, or an hour, at the longest. Often, indeed, the interval is
much shorter, and we have frequently seen dilatation of the cervix occur after one to two pains, and the expulsion of the infant ensue in a few minutes. The manner in which the amniotic fluid escapes depends on the quantity of fluid in the bag and on the point of rupture. If the bag is large, and if the rupture occurs, as it generally does, at the cervix, the liquid escapes with a gush. The patient feels herself moistened, and sometimes she feels the rupture or tear. It is especially in those cases which coincide with abnormal presentations, or high positions, that one sees prolapse of the cord, or of fatal parts. If, on the other hand, the bag is small and flat, while the foetal part is well engaged, or, if the rupture occurs at a variable distance above the cervix, only a few drops or spoons-full of liquid escape. It is not rare to see, in these cases, a second bag form later, at the os, and spontaneously or artificially rupture. In such a case it suffices to raise the head, or to pass the finger between the head and the cervix, to make a larger amount of liquid escape. When deep engagement has occurred, the foetus plugs the os, and the liquid escapes only intermittently. Tarnier and Chantreuil say that, in these cases, the escape occurs at the beginning of pains, but we think that it is at the end. The first effect of the pain is certainly to drive the liquid toward the cervix, but the foetus being more closely approximated to the cervix by the contraction, the liquid is unable to escape, and it is not until the stage of subsidence of the pain—that is, until the contact between the foetus and the cervix ceases to be close—that more liquid can escape. We will see, in a later chapter, the indications for artificial rup ture of the membranes, and the manner of performing this operation. It is generally easy to assure one's self that the membranes are ruptured, but we are sometimes in doubt. It has been suggested to examine during the pain, to assure ourselves that the bag of waters groWs tense. It has been stated that, when the membranes are applied to the head, the sensa tion which we experience is that of a polished, smooth surface, and that, in the opposite event, we feel the hair and the folds of the cranial tissues. These signs seem insufficient to us, and there is one which we consider much more certain, and which enables us to avoid errors which may be of danger for the child. This is to introduce the finger as high as possi ble between the head and the cervix. If the membranes are intact, no change occurs. If the membranes are ruptured, the finger, by slightly displacing the head, will make an empty space through which the liquid can escape, thus reaching the palm of the hand and leaving no doubt about the rupture.
The examination of the liquor amnii furnishes valuable information about the condition of the child. So long as the child is well, the liquid preserves its normal character, but if the child is ailing, meconium es capes, which colors the liquid a more or less dark yellowish green. Aus cultation will confirm or remove doubts, for this escape of meconium occurs normally and without danger to the child in pelvic presentations. If, however, the child has been dead for a certain time, the maceration which it undergoes in the sac formed of the membranes is accompanied by dermal vesicles filled with a sanguinolent fluid, or even with blood. These vesicles, rupturing, allow their contents to escape into the amnio tic fluid, which they color a more or less dark red, according to the time when the death of the fcetus took place. The liquor amnii at the same time grows inspissated and muddy.