It will be observed that the external rotation of the head is not an isolated fact, but that it is in consequence of the shoulders rotating in the inferior strait; and that this corresponds to the previous rotation of the shoulders in the superior strait simultaneously with this rotation of the head in the inferior strait. The face in these positions always appears on the right thigh of the mother. The right, or anterior shoulder is the first to appear in the fissure of the vulva; but the left, or posterior shoulder, is thee first to be set free by means of the perineum retracting from it, and it is thus in reality born first.
Thus mechanism of labor, the occiput being in the right half of the pubis, whether it be anterior, transverse or posterior, is all same usually as that just described. The same stage are passed through, but the rotations are not all from right to left; and consequently the face will appear at the thigh of the mother, instead of the right, as in the former case. When the occiput is at the right iliac sacral symphysis, it should always rotate to the front and appear under the arch of the pubis, precisely the same as when it is at the left sacro-iliac symphysis, which it sometimes fails to do, but slips into the hollow of the sacrum and remains behind till the completion of the labor, when the forehead appears under the arch, and the occiput is first disengages at the posterior commissure of the vulva.
It sometimes happens that when the occiput is in the hollow of the sacrum, the heed becomes gradually extended and the presentation becomes converted into one of the face.
Inclined, or irregular vertex presentations are usually aided in recovering a regular presentations by changing the mother’s position upon the same side of the inclination; thus if the sagittal suture is inclining far upon the right side, by tuning the patient upon the right side, the child’s body will fall down upon that side, and the inclination be rectified at once.
After the birth of the child, if inspection is made at once, it is always easy to tell the position it occupied from the sero- sanguineous tumor upon that part which presented. For the presenting part not being in contact with any thing, and pressure being made upon other parts, the fluids are forced into this parts; all of which soon subsides after the birth of the child. This sero-sanguineous tumor need not be mistaken for the cephalhaematoma; for the former exists at birth, the latter does not appear for some hours after; the former is large and purple; the latter smaller, the skin not discolored, it is fluctuating or pulsating and has an osseous border. The sero-sanguineous tumor does not exist if the child perishes long before birth, from which fact a medical jurist can draw an important inference in fixing upon the time of the death of a newly-born child
Facial Presentations. According to Allopathic authority, this presentation occurs about once in three hundred labors. The head, instead of being flexed upon the chest, is extended upon the neck, so that the face looks right down into the superior strait. In vertex presentations the occipital end of the long diameter leads the way in parturition; now in facial presentations the other end of the long diameter must lead the way, that is the chin, of course then the chin must become the point of departure. Then we have the left mento-iliac, anterior, transverse or posterior; or the right mento-iliac, anterior, transverse or posterior.
The cause of this unnatural presentation, except when it is produced by the accidental exchange of other presentations, can only be accounted for as the result of some previous conditions of the mother, which may be beyond our power to designate exactly.
This presentation, of the face, is diagnosed by feeling the depression of the eyes, the prominence of the nose, the mouth and the chin, and more especially by feeling the double gums and the intervening tongue. The relative position of the chin will also determine the exact position in this presentation.
Mechanism
As the right mento-iliac transversus is the most frequent of any of the facial presentations, we will describe the mechanism in this for all the others, since they are similar, only it should be remembered that the rotation will be from right to left, or the reverse, according as the chin is in the right or left iliac regions. After the liquor amnii has been discharged and the expulsive pains begin to operate, the first effect is to produce forced extension of the head upon the trunk, so that every pain has a strong tendency to break the child’s neck backwards. Descent now goes on, the chin leading the way, till its farther progress is obstructed by the breast coming in contact with the superior strait. Now rotation must commence and continue till the chin comes round in front sufficiently for the length of the neck to span the depth of the pelvis and the chin to pass under the arch. By this time complete descent and rotation have taken place, for the depth of the pelvis is here so shallow as to allow the neck to span it completely, and the crown of the head rests upon the floor of the pelvis, and this is the only point at which such a result can be obtained.
Flexion now begins to take place slowly around the symphysis, as a centre; and finally the chin rises up in front of the symphysis pubis, and the crown of the head descends on the anterior face of the sacrum and coccyx, and is finally disengaged at the posterior commissure of the vulva. External rotation is effected by the shoulders rotating into the inferior strait. Internal rotation causes the shoulders to place themselves in the long diameter of the superior strait. By no other means can a viable foetus be born, in facial presentations, than that rotation shall bring the chin under the arch of the pubis, unless the presentation itself should be changed into one of the vertex, or some other. Sometimes this actually does spontaneously take place, by the chin, when it is posterior, engaging in the sciatic notch; the progress of the child continuing, gradually flexes the head upon the trunk, and the vertex appears under the arch of the pubis, as in original vertex presentations. Inclined, or irregular facial presentations, when the chin, or one cheek is found in the centre of the superior strait, by continued contractions gradually regain the normal face presentation.
Facial presentations are by no means so safe for mother or child as are those of the vertex; yet in a very large majority of the cases they terminate favorably to both. The position is such that at every contraction the expulsive force upon the child is much diminished by the rolling back of the head upon the spine. Dilatation and rotation are not effected so rapidly on this account, and the child must of course remain, as a general thing, much longer in the pelvis.
Presentations of the Pelvic Extremity
We class as such presentations all those of the feet, knees, and breech, since in labor the same mechanism pertains to all alike. In the breech presentation, the sacrum forms the point of departure for determining the relative position; the anterior face of the tibia in presentations of the knees; and the heels, in footling cases. As in the vertex, or face presentations, the positions may be left sacro-iliac, or right sacro-iliac, and of the anterior, transverse or posterior varieties. Presentations of the breech are much more frequent than those of the face, and very much less frequent than those of the vertex; thus of sixty thousand four hundred and twenty-two cases reported, two thousand and eighty-two were breech presentations.
A breech presentation may be recognized, on digital examination, by feeling the cleft between the nates, instead of the sagittal suture, as in the vertex; in addition we find in the anus with its sphincter, instead of the fontanelles, a positive and not to be mistaken characteristic symptom. The coccyx and sacrum will enable us to decide as to the part of the pelvis they occupy, and consequently to determine the position exactly, when the feet, or one foot, presents, the heel will enable us to decide as to the position. It must be recollected that a foot is articulated at right angles with the leg, which feet alone will enables us to decide between the hand and foot, since the hand is in a straight line with the arm. The knees seldom present; but when they do it is easy to make them out from the popliteal spaces.
The Mechanism of Breech Presentations
The sacrum being left sacro-iliac anterior, and the membranes ruptured, the first stage is one of descent to the floor of the pelvis, the child’s legs, arms, and chin being folded in the same position as in the vertex presentation. The next stage is one of internal rotation, where the left hip comes under the arch of the pubis, and at the same time the shoulders are made to come into the long diameter of the superior strait. The next stage is the expulsion of the breech, during which time the child is strongly flexed upon its left lateral border, to correspond to the curve in the excavation of the pelvis. As the breech is delivered, the body descends with the arms folded up, and the chest and shoulders rotate into the long diameter of the inferior strait, the long diameter of the head passes through that of the superior strait, and finally rotates itself into the long diameter of the inferior strait; and the head is born with the chin still strongly flexed upon the chest, and the back of the neck and the occiput under the pubic arch.
