Diagnosis.—Causes.—Treatment.—Reposition of the cord.
Although by no means a common occurrence, it every now and then happens that a portion of the umbilical cord falls down between the presenting part of the child and the mother’s pelvis either just before or during labour; so that, as the child advances through the passages, its life is placed in imminent danger from the pressure to which the cord is exposed, obstructing the circulation in it.
There is probably no disappointment, which the accoucheur has to meet with more annoying than a case of this kind; every thing has seemed to promise a favourable labour; the presentation is natural, the pains are regular, the os uteri is dilating readily, the mother, and, as far as we can ascertain, her child, are in perfect health, and yet because a minute loop of the cord has fallen down by the side of its head, the labour, unless interfered with by art, will almost necessarily prove fatal to it.
Diagnosis. If the membranes be not yet ruptured, we shall probably be able to feel a small projecting mass like a finger, close to the presenting part, and possessing a distinct pulsation, which, from not being synchronous with the mother’s pulse, instantly declares its real nature. When the membranes give way, more of the cord comes within reach, and probably forms a large coil, which passes through the os uteri into the vagina, or even appears at the os externum.
Causes. The earliest writer that we know of who has given a detailed account of cord presention was Mauriceau; few, even in hospital practice, and certainly none in private practice, have exceeded him in the number of cases described, and very few have surpassed him in the success of his treatment. He mentions chiefly three conditions as being liable to produce prolapsus of the cord, viz. a large quantity of liquor amnii, an unusually long cord, and malposition of the child: later authors have enumerated several other causes, many of which are imaginary; of these, by far the most correct list has been given by Boer, of Vienna, who has justly ridiculed the theoretical views which were maintained by his cotemporaries.
“If there be a large quantity of liquor amnii present, and especially, as is not unfrequently the case, the child is at the same time under the usual size; if the head be not firmly pressed against the brim, and does not enter it sufficiently, or when the child’s position is faulty, especially if, at the same time, the cord is unusually long; if, under such circumstances, a large bag of membranes has formed, and the brim of the pelvis itself is very spacious; if perchance, the rupture of the membranes takes place at a moment when the patient is moving briskly on in some unfavourable posture, the cord will be very liable to prolapse. Nevertheless, cases are occasionally seen which arise without these predisposing circumstances.” (Boer, von Geburten unter welchen die Nabelschnur vorfällt.)
The uterus is the chief means by which the cord is prevented from falling down between the presenting part of the child and the passages, from the closeness with which its inferior portion encircles it: without this, from the erect posture of the human female, there would be a liability to prolapsus of the arm or cord in every labour.
“The contraction of the uterus, which comes on with the rupture of the membranes, and sometimes, where they protrude very much, even before, is of great importance. This contraction takes place in the inferior segment of the uterus; it surrounds the head, and when fully developed extends over the whole head of the child. Thus, for instance, if we attempt to operate at an early stage, it feels more like a hard ring round the head, of about a finger’s breadth, and it may be felt to extend itself higher up, in proportion as the stimulus of the hand excites the activity of the uterus.” (Michaelis, Neue Zeiteschrift für Geburtskunde, band iii. heft. 1.)
Hence, therefore, whatever prevents the uterus from contracting with its inferior segment upon the presenting part of the child, deprives the cord of its natural support, and, therefore, renders it liable to prolapse. Many of the causes enumerated by Boer act in this way; thus, where the uterus is distended by an unusual accumulation of liquor amnii; where the contractions at the beginning of labour have been exceedingly irregular; where the arm, or shoulder, or feet present; or where a large bladder of membranes is formed, the lower part of the uterus will either not contract at all upon the head, or so imperfectly as to endanger the descent of the cord.
Malposition of the child has been mentioned by many authors as a cause of prolapsus of the cord, and in some cases it may possibly act thus from the inferior segment of the uterus being unable to surround sufficiently close so irregular a mass as the shoulder. In the majority of cases, however, the coincidence of these two circumstances depends upon their being produced by the same causes; thus an unusually large quantity of liquor amnii, or irregular contractions of the uterus, will just as much dispose to the one as the other.