A System of Midwifery

by Edward Rigby

The pelvis may obstruct the passage of the child in a variety of ways.

1. It may be merely a diminutive or dwarfish pelvis, viz. well formed but smaller than usual in every direction—the pelvis simpliciter justo minor of Continental authors.

2. It may be distorted and deformed.

3. It may be of the natural form and size, but the passage through it more or less obstructed by exostosis.

Equally contracted pelvis. The first species of faulty pelvis (pelvis simpliciter justo minor,) is not of common occurrence, and has received but little notice in this country. It has been said to resemble the pelvis of a girl in its general appearance; but this only holds good in point of size; for, in the relative proportions of its diameter, it presents all the characters of a well formed adult pelvis. From this circumstance, it can scarcely be said to be an arrest of development, the necessary changes in the form of the pelvis having taken place at the time of puberty, as completely as if it had been of the ordinary size. A pelvis of this sort may be not more than a quarter of an inch too small in every direction, or it may be as much as a whole inch: we do not know of any case where the diminution has exceeded this last degree.

The pelvis equaliter justo minor is not accompanied with a corresponding diminutiveness in the rest of the skeleton, most of the patients in whom it has been observed being well formed and of the usual stature. Fortunately, as before stated, it is of rare occurrence, for even a small diminution in the size of the bony passages, which is uniform in every direction, presents a most serious obstacle to the passage of the child. Thus, in three cases of the sort, which have been described by Professor Busch in his report of the Berlin Lying-in Hospital, the labour terminated fatally in two. “The first case was a presentation of the breech; the head was delivered by the forceps; the child was dead; the pelvis measured half an inch too small in every direction. In the second case, which was a head presentation, the delivery was effected by the forceps, but not without the greatest efforts; the child was still-born, and the mother died in a day or two after from peritoneal inflammation. The third case required perforation; this also terminated fatally, the forceps having been previously applied, and considerable efforts made without success. On examination after death, every diameter of the pelvis was three quarters of an inch smaller than usual: in appearance it resembled that of a child.” (Neue Zeitschrift für Geburtskunde, vol. xv. 1837.)

Unequally contracted pelvis. The unequally contracted pelvis (pelvis inæqualiter justo minor) may exist under a variety of forms; the most common is where the antero-posterior diameter is defective, or, in other words, where the distance between its anterior and posterior parietes is less than usual. In a slight degree, it is frequently met with among the poorer classes, and arises from the patient having been compelled to carry heavy burdens in early childhood, or otherwise subjected to severe labour. The practice of entrusting a girl of eight or ten years of age with the care of a heavy infant, which she carries about in her arms for many hours every day, is a fruitful source of this species of pelvic deformity; the young and plastic pelvis is unable to bear the additional pressure which is thrown upon the sacrum by the overloaded trunk, without having the just proportions of its growth materially influenced and perverted, especially at a period of life when the whole form of the pelvis is undergoing considerable changes. The constant pressure and counter-pressure to which the pelvis is subjected by the undue weight which is applied to the sacrum above, and supported by the resistance of the femora against the acetabula below, must necessarily tend at this age, even in an ordinary state of health, to impair its symmetry, more or less, and gradually to diminish the distance between its anterior and posterior parietes. Under no circumstances has this cause of pelvic deformity acted to such an extent as in the English manufactories, where young children are compelled to remain standing for twelve or more hours at the machines: the physical powers are unequal to the endurance of so much unceasing labour, the skeleton of the child soon suffers in its growth, and the pelvis almost certainly becomes contracted.

Similar effects may also be produced by undue pressure on the other parts of the pelvis. Thus the outlet may become much contracted by sitting many hours a day on a hard seat, as is frequently the case in schools. The tubera ischii are pressed together, the pubic arch is thereby contracted, and the sacrum becomes strongly curved forwards. Much riding on horseback at an early age is said to be injurious; and it is stated that the females of those American nations who are constantly on horseback bear but few children, and are frequently three or four days in severe labour.

Rickets. Similar effects, only in a much more aggravated form, are produced by rickets in early life; the pelvic bones having become soft from the loss of their earthy matter, gradually give way under the pressure of the superincumbent trunk, to the support of which they were unequal. In this way the sacrum is forced downwards and forwards towards the symphysis pubis, the acetabula are driven upwards and backwards, the pubic arch becomes distorted; and if the disease continues for a considerable period of time, the whole pelvis becomes so squeezed together as entirely to lose its original proportions.

The manner in which the distortion takes place varies exceedingly, and will be more or less influenced by the circumstances under which the child has been placed. The most constant change is the shortening of the antero-posterior diameter at the brim. In severe cases the base of the sacrum has, as it were, sunk down between the illia, so that its promontory occupies the cavity of the pelvis, the fourth, or third, or even the second, lumbar vertebræ occupying its former position. The gradual yielding of the bones seldom takes place with that degree of uniformity as to allow the sacrum to approach the symphysis pubis in a straight line: the more common result of rickets is, that the promontory is, at the same time, wrung more or less to one side.