LABOR IN CASE OF PELVIC DEFORMITY.
At first we will study the general course of labor, and afterwards the march in special varieties of pelvic deformity.
The phenomena of labor are divided, even as in normal cases, into physiological and mechanical.
For the purposes of our study, we will divide pelvic deformity, with Naegele and Grenser, into three great classes: 1. Although the pelvis is contracted, it allows of expulsion of the foetus by the efforts of nature. The risk to both mother and infant is, how ever, increased.
2. The contraction does not prevent engagement of the head at the superior strait, or in the cavity, but the head cannot entirely pass.
3. The contraction is of such a degree that the head cannot enter the superior strait, and remains movable above it.
In pelvic contraction, aside from the factors requisite in normal labor, regular and good contractions, there are two on which great stress must be laid: The degree of contraction, and the reducibility of the foetal head.
Physiological Phenomena.
a. Uterine Contractions.—In general, it may be said that these are proportionate to the resistance to be overcome. At first they are normal and regular, but it is not rare to see them assume an extreme intensity, yielding soon to feebleness and irregularity, merging finally into uterine inertia. These irregularities, of course, are most marked where the con traction is considerable, and labor of long duration.
The obstacle once overcome, not infrequently labor is speedily finished; in other cases, however, the uterus, tired out by its efforts, sinks into complete inertia. Whatever the case, both too energetic and too feeble contractions are fraught with danger. If they are too energetic, rupture of the uterus may result; if they are too feeble, the head does not engage, and labor is prolonged to the detriment of both the mother and the child.
Whatever the nature of the contractions, what strikes us particularly is the tardiness with which the head engages, a tardiness dependent not alone on the contraction, but on the overhanging abdomen, whence the head does not correspond to the pelvic inlet. This engagement of the head is exceptional before labor, in case of deformed pelvis. Litzmann in 222 women, found it only partially engaged 18 times during pregnancy; dur ing labor in only about 24.1 per cent. of the cases; in 56 per cent. en gagement only occurred after complete dilatation of the cervix. Vaginal touch, therefore, at the beginning of labor, does not allow us to reach the presenting part, which remains above the superior strait. Only by forcibly depressing from above, can the finger touch a small segment of the vertex.
b. Dilatation of the Cervix.—This occurs slowly, often very slowly, on the one hand on account of the little intensity of the contrac tions, and on the other because the membranes usually rupture prematurely, and, therefore, mechanical pressure is largely absent. As long as the membranes are intact dilatation proceeds regularly enough, but when these rupture, the cervix thickens and dilates very slowly. The cervix itself presents certain peculiar characteristics.
Instead of being thin, as normally is the case, it remains thick; the os rarely exceeds in dilatation the size of a quarter, but we find that ,it is perfectly dilatable. This happens because the head has not pressed on the cervix, but has remained above the superior strait. Under the influence of the contractions, however, the head becomes more and more moulded and becomes partially pointed, and engages a trifle. At this part of the head the caput succedaneum forms, and projects the more the longer the duration of labor. The cervix is filled with this herniated, as it were, caput, and the cervix forms a ring around it, even where the head remains above, or nearly so, the superior strait.
c. Membranes.—The head being retained above the superior strait, the liquor amnii may collect in front of it, and therefore the bag of waters is always voluminous. If the resistance of the membranes is considera ble, it is an efficient factor in dilatation, until they rupture, and this usu ally happens before the os is more than one-sixth dilated. It is at the moment of rupture, especially if the woman is in the erect position, that prolapse of the limb or the cord occurs, the presence of which, above the superior strait, we may occasionally recognize before rupture. When, however, the membranes are elastic, the appearance and sensation is different. The bag of waters does not form within the cervical canal, but outside, and the projection is the more the greater the elasticity of the membranes. On touch, at first sight, it seems as though dilatation were completed, but on carrying the finger higher, the constricting cervix is felt.
In each instance, however, the membranes rupture prematurely, and before dilatation has occurred, and, in consequence, labor is prolonged, and the foetus is exposed to the dangers resulting from interference with the uterine and placental circulations.
Occasionally, the membranes rupture even before the onset of labor, under the influence of the painless contractions.
Rupture having occurred, the cervix retracts, although it remains dila table to the same degree. Then either: 1. The obstacle to delivery is insurmountable; the contractions become very energetic, and, if we do not interfere, the uterus, rarely, fortunately, ruptures, or the vagina is detached at the vaginal vault. There follows, usually, however, uterine inertia.
2. The obstacle to delivery is not absolutely insurmountable, the head tends to engage, it moulds itself gradually, and sometimes passes the superior strait. Again, on the contrary, engagement may be only partial, and the head remains imprisoned, as it were, until art assists it.
How now, and by what diameters does the head engage? If we in terfere, is forceps or version preferable? These questions we will success ively pass in review.