The two greatest Continental authorities of modern times, viz. Madame La Chapelle and Professor Naegelé, confirm this opinion: the former points out one of the sources of error which has induced practitioners to suppose that they had met with other species of faulty presentation besides those of the arm or shoulder. “In the greater number of shoulder presentations,” says this experienced authoress, “I have very distinctly touched the chest, in some positions of the nates I have been able to reach the loins, the hips, or lower part of the abdomen; but it would require no slight bias from prejudice and theoretical systems to find presentations of the chest, the back, the abdomen, or the loins, the neck or the ear.”[108]
We would, therefore, limit the term malposition of the child merely to presentations of the arm or shoulder: other presentations, it is true, occur, but not of the full-grown living fœtus; they are only where the child is premature, or has been dead in utero some time. Under such circumstances it will follow no rule whatever; for in the first case it is too small, and therefore the passages can have no effect in directing its course through them; and, in the second, a child which has been dead some time becomes so softened by gradual decomposition, that it may be squeezed by the pressure of the uterus into almost any shape: it is by this cause that we occasionally see in still-born children parts in close contact, which in a living child could not have been brought together.
We do not deny that such presentations may be made by ignorant and awkward attempts to deliver, but it is to be hoped that such cases are daily becoming of rarer occurrence.
Malposition of the child is fortunately not of very frequent occurrence: as a general average we would say that it occurs once in 230 cases, as the following results will show:—At the Westminster General Dispensary (1781) it occurred to Dr. Bland once in 210 cases: at the Dublin Lying-in Hospital, to Dr. Joseph Clarke, once in 212: in private practice, to Dr. Merriman, once in 155: “calculated from a great number of cases,” to Professor Naegelé, once in 180: at the Dublin Lying-in Hospital, to Dr. Collins, once in 416: at the Maternité, of Paris, to Madame La Chapelle, once in 230.
In arm and shoulder presentations the back of the child is turned towards the anterior part of the uterus more than twice as frequently as it is in the contrary direction, from which circumstance Professor Naegelé has called this the first position of the shoulder to distinguish it from the other, which, as being rarer, he calls the second.
In investigating the nature of the causes which produce malposition of the child, which, from the above observations, is evidently a circumstance of rare occurrence, the question naturally suggests itself, by what means is the long diameter of the child in so large a majority of cases kept parallel with that of the uterus? This depends in great measure on the form and size of the uterus. Where the uterus is not unduly distended with the liquor amnii, and where it preserves its natural oval figure, it is scarcely possible that the child should present in any other way than with its cephalic or pelvic extremity foremost. There can be no doubt that the first early contractions of the uterus in the commencement of labour have a great effect in regulating the position of the child; for, by the gentle and equable pressure which they exert upon it, they not only maintain it in the proper direction, but tend materially to correct any slight deviations from the right position. Hence, therefore, we find that where any cause has existed to impair or derange the action of these precursory contractions of the uterus, the child is apt to lie across, or, in other words, to present with the arm or shoulder. Thus, for instance, if the uterus be much distended with liquor amnii, the contractions of its parietes can have little influence upon the child’s position; this will be particularly the case where the accumulation is very considerable, for here the uterus becomes more or less globular, and presents but little variation as to the length of its diameter in any direction.
The form of the uterus is no less worthy of attention as a cause of malposition, and is also in a great measure influenced by the character of its early contractions. Thus in a uterus for the first time pregnant, they generally act equally on all sides: hence it is why in primiparæ the uterus is so exactly oval, and why we so rarely meet with faulty presentations. Sir Fielding Ould, of Dublin, was the first and almost the only practitioner in this country who noticed the influence which the early contractions of the uterus have in determining the position of the child. “The first labour pains, which are very short, continue their repetition for two or three hours, or perhaps for more, before there is the least effect produced upon the os tincæ, which time must certainly be employed in turning the head towards the orifice.” (Treatise of Midwifery, p. 14.)
Wigand, in reasoning upon the physical impossibility of a child presenting wrong, where the uterus is of the natural configuration, says that “the chief cause of faulty position of the child does not depend so much upon the child itself, as upon the deviation of the uterus from its natural elliptical or pyriform shape.” (Wigand, vol. ii. p. 107.)
The theory at one time so universally entertained, that the obliquity of the uterus was the chief cause of malposition of the child, has long since been disproved, although it continues to find a few adherents to the present day: the uterus, in fact, towards the end of pregnancy, is scarcely ever quite straight; the upright posture of the human female rendering it almost necessary that the fundus should incline somewhat to one side or to the other, or forwards, and yet we find that it has no influence upon the position of the child when labour comes on. The moment a pain commences, the fundus moves towards the median line of the body, so that its axis corresponds nearly with that of the pelvic brim: as the pain goes off, so does it return towards its former oblique position. Even in those cases where it is strongly inclined forwards, and where the abdomen is quite pendulous, the position of the child is unaffected by it.
Where, however, the uterus has been altered in point of form, where from irregular contractions of its fibres it has been pulled down unequally to one side, while it is quite relaxed in the opposite direction, the position of the child may be seriously affected, for it will now present obliquely as regards its long axis, and become a case of malposition.