A System of Midwifery

by Edward Rigby

We consider that to form an accurate diagnosis in these cases, requires the highest perfection of the tactus eruditus, which can only be acquired by long practice and patient observation: and it is chiefly from this circumstance that we can explain why such gross errors and vague notions should have existed about a process of every day occurrence, and why, with but few exceptions, they should have been transmitted from one author to another even up to the present time. In the last century, when it was so much the fashion to resolve every physiological process into a mathematical problem, it was scarcely deemed necessary to spend much time in actual observation and examination; the proportions between the head and pelvis were ascertained, their angles were measured, and their curves determined, and from these data it was inferred, what must be the course which nature would follow; few attempted the slow but surer method of ascertaining by patient research the real facts connected with the process of parturition.

When the long axis of the child’s body corresponds with that of the uterus, the child (provided the passages are normal) can be born in that position: it matters little, as far as the labour is concerned, which extremity of the child presents, so long as this is the case; but where the long axis of its body does not correspond with that of the uterus, the child must evidently lie more or less across, and will present with the arm or shoulder, a position in which it cannot be born. In stating this, we wish it to be understood, that we merely refer to the full grown living fœtus, and not to one which is premature, or which has been some time dead in the uterus, as these follow no rule whatever, hence the positions of the child at the commencement of labour resolve themselves into two divisions, viz. where the median line of the child’s body is parallel with that of the uterus, and where it is not; the first we shall call natural, the second faulty, presentations of the child. A description of the natural presentations will form the contents of the present chapter.

The reader will almost anticipate us when we state, that the natural presentations consist of two classes, those where the cephalic, and those where the pelvic end of the child presents; in the first case, it will be a presentation of the cranium or of the face; in the second, of the nates, knees, or feet.[77]

Cranial presentations. The presentation of the cranium, (or vertex, as it has been improperly called,) is of by far the most frequent occurrence; thus, for instance, of 4042 children which were born in the lying-in hospital, at Heidelberg, 3834 presented with the head; of these the 3795 with the cranium, and 39 with the face: in either case, whether it be a presentation of the cranium or of the face, it will be either with the right or the left side more or less foremost; the former, from its greater frequency, has been called the first position of the cranium or face, the latter the second position.

First cranial position. It will be recollected we have stated, that the os uteri at the end of pregnancy is turned obliquely backwards, corresponding to the upper part of the hollow of the sacrum. If we examine during the first stage of labour, when it is just dilated sufficiently to allow the finger to pass, we shall feel the sagittal suture of the head running across it, dividing it into two unequal portions, the os uteri itself corresponding nearly to the middle of this suture. If the os uteri be sufficiently dilated to let us trace its course, we shall find that it corresponds more or less to the direction of the right oblique diameter, viz. that it runs from the right and backwards, obliquely forwards, and to the left. If we follow it with our finger in this last-mentioned direction, we come to a spot where it divides into or meets two other sutures; these are the right and left lambdoidal sutures, and beyond them is the hard convex occiput, the point where they meet being the posterior or occipital fontanelle. If we trace our finger along the suture in the other direction, viz. backwards and to the right, we shall come to a four cornered space, where four sutures meet at right angles to each other; these are the sagittal, the frontal, and right and left coronal sutures; the open space itself is the great or anterior fontanelle.

That part of the head which lies lowest or deepest in the pelvis, and which the finger first touches upon when introduced along the vagina, is the right parietal protuberance; and if the os uteri be sufficiently dilated, we distinguish it by its hard and conical feel. In primiparæ, where the head usually is deep in the pelvis at the commencement of labour, and where the anterior and inferior segment of the uterus is closely stretched over it, the parietal protuberance may be felt through this part. Hence, then, the first position of the cranium, (or more correctly speaking, parietal bone,) is marked by the following characters: the sagittal suture crosses the os uteri, and runs parallel with the right oblique diameter of the pelvis: the vertex is therefore turned towards the upper part of the hollow of the sacrum, the posterior fontanelle forwards and to the left: the right perietal protuberance, therefore, is necessarily that part which is deepest in the pelvis; and the perpendicular diameter of the head, instead of corresponding to the axis of the pelvic brim, runs in an oblique direction upwards and forwards.

If the head at this early stage of labour be high up in the pelvis, viz. has scarcely entered the brim, as is frequently the case in multiparæ, the sagittal suture approaches in its direction to that of the transverse diameter, or to one between the transverse and oblique diameters, the posterior fontanelle corresponding to about the left acetabulum. The higher the head is in the pelvis, the nearer does its greater diameter correspond to the transverse one of the pelvis: the more oblique also is its perpendicular diameter, from which reason the right ear at this time can usually be felt without difficulty behind the pubic bones. Sometimes both fontanelles can be reached with equal ease; most frequently the posterior one is lowest, but occasionally the reverse is the case, and it is the anterior fontanelle, without, however, at all influencing the progress of the labour.

As the head advances through the brim and begins to enter the cavity of the pelvis, the sagittal suture corresponds more closely with the right oblique diameter, so that now the posterior fontanelle is turned towards the left foramen ovale, and as it approaches the outlet of the pelvis, the occiput advances still more forwards, although the head entirely quits its oblique position. At this stage of the labour, the fontanelles can usually be again reached with equal facility, and we find the anterior one corresponding to the right sacro-iliac synchondrosis, the occiput is completely behind the left descending ramus of the pubes, the right lambdoidal suture running parallel with it. Owing to this slight change in the position of the head, the occiput having advanced somewhat forwards, we no longer feel the right parietal protuberance to be lowest and in the centre of the pelvis, but the finger now touches upon the posterior and superior quarter of the right parietal bone, for this is the part of the head which first comes under the pubic arch, and first enters the external passages.

If there be but little liquor amnii, or the membranes have been ruptured prematurely: if the head be firmly pressed against the os uteri, and we examine when it is not more than two-thirds dilated, we feel a puffy œdematous swelling upon that part of the head which corresponds to the os uteri. This will therefore be found to be situated upon the sagittal suture, nearly equidistant from the anterior and posterior fontanelles; it arises from the circulation in the scalp being obstructed by the pressure of the os uteri upon the head. If the remaining portion of the labour be rapidly completed, this will be the situation of the swelling with which the cranium is born; if, however, it follows a more gradual course, and the head passes slowly through the os uteri into the vagina, as it thus advances deeper into the pelvis, and alters its position more or less, the swelling upon the sagittal suture disappears in part, and forms on that portion of the head which is advancing under the pubic arch, and is now tightly encircled by the external passage: we shall, therefore, find that this second swelling is situated upon the posterior and superior quarter of the right parietal bone, and this is precisely the situation of the swelling of the head, which the child is usually born with.

From these facts we may deduce the following simple law respecting the mechanism of parturition, where the head presents: viz. that the head enters, passes through, and emerges from, the pelvis obliquely; and this is the case not only as to its transverse diameter, but also as to the axis of its brim; the side of the head being always lowest or deepest in the pelvis. This shows the beautiful mechanism of the process, for, on account of its oblique position, there is no moment during the whole labour at which the greatest breadth (still less length) of the head is occupying any of the pelvic diameters; even at the last, when the head is passing under the pubic arch, the complete obliquity of its position, in order that it should take up the least possible room, is very remarkable; for the ring of soft parts, by which the head is now encircled, passes obliquely across it, running close behind the left, and before the right parietal protuberance. The head never advances with the occiput, forwards, under the pubic arch, as is stated in works on midwifery, still less with the sagittal suture parallel to the antero-posterior diameter of the pelvis; for the direction of the right lambdoidal suture, as also of the posterior fontanelle, and the position of the cranial swelling, or caput succedaneum, as it has been called, completely prove the inaccuracy of such a theory, the sagittal suture crosses the left labium at an acute angle, the right lambdoidal suture being parallel with the left descending ramus of the ischium.