MECHANISM OF DELIVERY IN PRESENTATIONS OF THE FACE.
Presentations of the face appear to result from the head being bent
backwards, instead of forwards upon the chest. They are easily
recognized, because the face has so many peculiar parts, as the nose
and mouth, for instance, which are altogether unlike what can be felt
in any other presentation. In a very early stage the forehead may be
taken for the vortex, unless care be used, because it _feels_ round and
soft like it, but the mistake cannot last long.
The positions in this presentation, as formerly explained, are
determined by the chin, and in practice only two are noticed--the
_right posterior mento iliac_, and the _left anterior mento iliac_.
In the first the chin is on the right side, near the sacrum, and in
the second it is on the left side, near the pubes. These answer, it
will be seen, to the two principal positions of the head itself. It
is generally considered that, though the chin, like the head, may
assume other positions, yet it does so in but very few cases, and these
presenting no peculiarities which require special notice.
DELIVERY IN THE RIGHT POSTERIOR MENTO ILIAC POSITION OF THE FACE.
The head descends with the forehead and chin nearly on a level, and the
nose occupying the middle of the passage. When fairly in the cavity
it rotates, the chin being brought under the pubes, while the back of
the head passes into the curve of the sacrum. This is nearly always the
process; no matter where the chin may be when the labor commences, it
seldom fails to move under the pubes before it concludes. Occasionally
it may rotate the other way, and pass into the hollow of the sacrum,
while the occiput comes in front, but this is very rare.
The chin is born first, and then follows, below, the forehead, top of
the head, and finally the occiput--the face turning upwards towards
the mother's abdomen, as each part is successively delivered. When the
head is fully born, the body rotates inside the same as in the head
presentation, and the delivery concludes in precisely the same way.
[Illustration: PLATE XXXIV.
Fig. 1.--The chin just passed, in presentation of the face.
Fig. 2.--The head full born in presentation of the face.--_p._ The
Pubic bone.--_c._ The Coccygis.]
DELIVERY IN OTHER POSITIONS OF THE FACE.
The delivery is precisely the same in all the other positions of the
face, excepting that in some of them the chin has further to rotate
before it can pass under the pubes. In all cases however, it may
be safely calculated that it will do so, there having been so few
instances known in which it has rotated the other way, into the hollow
of the sacrum, which is fortunate, for there is always more or less
difficulty and danger when it does so.
Sometimes the rotation does not take place at all, but the face
descends diagonally, as the head occasionally does.
On the whole presentations of the face are not particularly to be
feared, as regards the mother. Some authors even consider them quite
favorable, and reckon them only as varieties of the head presentation.
Madame Lachapelle states as a principle, that face presentations should
always be left to nature. And M. Chailly says he must admit that, in
all positions of the face, the labor may terminate spontaneously,
excepting when the chin passes behind, in which case it will be
protracted, and most likely fatal to the child. The labor is generally
a little longer, and more painful, owing to the face not being so
perfectly adapted to the passage as the head is; but still it must
be regarded as favorable to the mother, though assistance is oftener
required than with the head. There is more or less danger to the child
however, owing to the head being kept under pressure for an unusual
time, which produces congestion. The neck is also forced against the
pubic bone, as will be seen by Figs. 1 and 2, Plate XXXIV, and thus the
jugular veins are compressed. If there be any delay, it is customary
to observe the face closely, after the chin is born; and if it appears
from any indications that congestion is taking place, assistance is
rendered at once. The face will sometimes become so tumefied, and
engorged with blood, from this prolonged pressure, that it will not
appear natural till several days after birth.
Probably about one child is lost in ten or twelve deliveries in these
cases; and if the chin pass behind its death is almost certain.
It was formerly the practice to endeavor to turn the face upwards,
when at the superior strait, and so change the presentation to one
of the head. This however, is now abandoned, because the attempt is
seldom successful, and does not materially improve the condition of
things, besides being painful to the mother. The only extra danger
with the face presenting is to the child, and this is not removed by
the operation; to the mother the face is nearly as favorable as the
cranium. In regard to the frequency of face presentations, we find that
Madame Lachapelle met with but _seventy-two_ cases in _fifteen thousand
six hundred and fifty-two deliveries_.