A pain in labor signifies the contraction of such muscular fibres as are concerned in giving to the child; and the sensation of pain produced in such contractions results from pressure upon the nerves distributed in the tissues, especially of the uterus itself, thus contracting. The sensation of the is felt in the back, abdomen and elsewhere, by virtue of reflex action, but which the seat of the pain is located at the central origin of the nerves themselves, rather than at their peripheral terminations. During the entire course of the parturition, the child takes no part in its delivery, it is entirely submissive, as it has been during its entire stay in the uterine cavity; it is entirely neutral and passive, and is expelled entirely by the last act of reproduction on the part of the mother.
The more active the muciparous glands in this vital act, the more easily is the child brought forth; the abundant glairy discharges rendering the labor a moist one and comparatively easy; where little or none of this mucus is secreted the labor is called dry, and is consequently more painful and tardy.
The bag of waters, known as such, is simply the amnion and chorion distended in advance of the presenting part of the child, by the bulging of the liquor amnii in consequence of the pain.
The duration of labor is exceedingly variable, even when no obstacle seems to oppose the delivery, from one hour or to a week; and between these two extremes there is every intermediate grade. In general, labor is longer in primiparae than in those who have had many children, or are nearer the climacteric period of life. As a general rule, the average length of time may be set down at from six to twelve hours. The duration of the labor is expected to be announced as soon as an examination is made per vaginam. But much caution should be used in this matter, for it is discouraging to the patient to overrun the specified time. After the first stage is passed, the second will be two or three times shorter, other things being equal, the diameter of the straits all being normal and there being no undue rigidity of the soft parts. In other cases, the time will very, according to the changes conditions. It is, after all, utterly impossible to predict the time of delivery with certainty.
The Effect of Labor upon the Mother and Child. On the part of the mother there is often much despondency at the commencement of labor; and during the first stage there is apt to be more or less distress of body and mind, a feeling of despair, as if she could not endure to the end. But, as soon as the second stage sets in, the patient nearly always raises her spirits, she becomes more hopeful and bears her pains, and voluntarily exerts herself, with confidence that she will be delivered all right. She often perspires profusely and becomes much exhausted during labor. The whole process of parturition is certainly very shocking to the nervous system, and there is danger of great prostration during delivery, similar in effect to the produced in persons sustaining a severe mechanical injury, even a complete collapse may sometimes occur. Great care is needed, immediately after the completion of this great event, that the patient get quite sleep as soon as possible. She should no be allowed to talk, and much less should the accoucheur try to have a little pleasant conversation with her after the labor is over. Such a course cannot to too severely censured, since it may be attended with fatal consequences. A little sleep makes all safe.
On the part of the child, the effect of the labor varies with its severity and its duration. And the shock of the compression of the uterine contractions is more severely felt upon male than upon female children, as before stated; in many cases, the sad effects are immediate; in others, more remote, and proportionally more injurious.
The mechanical phenomena of labor have relation strictly to thee child. It is very evident, from the knowledge we possess of the form and mechanism of the pelvis and also of the child, that there must be a mechanical adaptation of the latter to the former, in order that it can be born; and that, in order to secure this result, there must be certain presentations and positions at the superior strait.
Almost any part of the child may present at the superior strait, making almost an infinite variety of presentations; but, for all practical purpose, it will be sufficient to describe only five. For, when the accoucheur recognizes either of these, he will be able to determine what, if any, mechanical means may be needed to produce relief.
Each of the five presentations may have one of six positions, as for instance, in the vertex presentation, the occiput must lead the way in labor, since it is one end of the head. Then we describe the occiput as being in the left iliac region, anterior, transverse, or posterior; or the right iliac, anterior, transverse, or posterior. That is to say, the position is left occipito-iliac, anterior, transverse, or posterior, according as the occiput is in the half of the pelvis and at the ileo- pectineal eminence, exactly transverse across the pubis, or at the sacro-iliac symphysis. The same terms would be applicable in all respects, if the occiput were in the right half of the pubis, and at those various points respectively.
In facial presentations the chin would lead, then of course the position would be styled, right mento-iliac, anterior, transverse, or posterior, if in the right half or the left mento-iliac, anterior, transverse or posterior, if in the left.
In presentations of the breech, the sacrum is the point of departure. and is called according to circumstances, the right or the left sacro iliac, anterior transverse or posterior, position.
In presentations of the the right lateral plane, the head must be either in the right or left half of the pubis, and the position must be called the right cephalo-iliac, anterior, transverse or posterior, according to circumstances; and similarly in the left half of the pubis. In presentations of the left lateral plane, the same terms, according to circumstances, must express the position with sufficient accuracy for practical purposes. Each of these presentations will now be particularly explained.
The Vertex Presentations. This occurs very much more frequently than all the others put together; for instance, of twenty-two thousand five hundred nd thirty-seven carefully observed cases, only eight hundred and fourteen were found to be of any other presentation. And of the vertex presentation the very much larger proportion of cases is found to be in the left occipito0iliac anterior position. This position, which occurs the most frequently, is found to be the easiest and most natural of all.
The diagnosis of the vertex presentation is made out by feeling a large, round, hard, smooth tumor, while examining per vaginam, either at the superior strait, or descending into the cavity of the pelvis. The stethoscope will also reveal with much certainty the presentation of the vertex, by the beat of the foetal heart being heard low down in the abdomen. The vertex presentation being made out, it remains to define the position by means of the position of the fontanelles and sutures.
By carrying the finger a little backward and upward on the head the sagittal suture will be encountered, and if it runs from before backwards, from left to right, and if the anterior fontanelle is towards the right sacro-iliac symphysis, the position must be left occipito-iliac anterior. But if the anterior fontanelle is found to be at the left ileo-pectineal eminence, the position must be right occipito-iliac posterior. Either fontanelle, anterior or posterior, may be ascertained by tracing along on the sagittal suture each way, backwards or for wards. In this manner are all the positions of the vertex presentations ascertained.
The mechanism of labor where the position is with the occiput in the left half of the pelvis, is usually the same in all cases. The occiput being left anterior, transverse or posterior, the contractions having begun and the liquor amnii having partially escaped, the first effect upon the child is to flex the head more perfectly upon the chest, which constitutes the first stage in mechanism of labor. This has the effect to bring the long diameter of the head in harmony with the axis of the superior strait. The second stage is completed when the head descends into the cavity of the pelvis till its crown presses upon the plane of the pelvis. The third stage and rotation is accomplished from left to left to right, till the progress of the head is arrested by the back of the neck resting upon the symphysis pubis. During the fourth stage, extension of head upon the neck takes place, and the head is born by the occiput slipping up in front of the symphysis pubis, and the perineum retracting from over the forehead, face and chin of the child. Now the fifth and last stage in the mechanism of labor is accomplished, by the shoulders rotating into the long diameter of the inferior strait, which produces external rotation of the head, and the child is delivered.
