MECHANISM OF DELIVERY IN PRESENTATIONS OF THE LOWER EXTREMITIES.
This presentation includes the feet, the knees, the breech, and also
the hips, there being no difference in the delivery for all these
parts. It is the same also whether there be one foot, or knee, or both
feet and knees.
There are but two positions worthy of notice in this presentation,
and they are determined by the child's sacrum. If the sacrum, or
posteriors, are to the right of the mother's Pelvis, it is called the
_right sacro iliac position_; but if they are on the left side it is
called the _left sacro iliac position_. The direction in which the
child's pelvis is placed, is analagous to that of the head, the sacrum
answering to the occiput. Thus most frequently the sacrum is on the
left side, a little to the left of the pubes, (_left anterior_) while
the abdomen faces the right side near the sacrum. When on the right
side however, it is most usually nearest the sacrum, with the abdomen
facing the left side near the pubes.
The lower extremities present most frequently next after the head, but
still they are but seldom met with. M. P. Dubois tells us that out of
_twenty thousand labors_ he only met with _eighty-five_ such cases. In
these eighty-five cases the breech presented _fifty-four_ times, and
the feet _twenty-six_, the knees being found _but once_.
A presentation of the lower extremities may generally be recognized
at an early stage, by the head being felt at the _fundus_ of the
Uterus, and by the pulsations of the fœtal heart being heard above the
umbilicus, as explained in the section on Auscultation. After labor has
commenced the part felt at the mouth of the Womb is irregular, and so
different from the head, that it is not likely to be mistaken for it.
If the knees or feet present, they can always be distinguished; and
if the breech presents it can easily be recognized by its form, and
particularly by the os coccygis, which can be distinctly felt at the
bottom of the depression between the two cheeks. The side on which it
is felt of course determines the position, and the same with the front
of the knees, or the heels. The Rectum can also be reached with the
finger, when the breech is touched; but great care must be taken not
to intrude it too far, because with a female child the _Vulva_ might
be mistaken for it, and thus the hymen be broken, and other injury
committed. The genitals of a male child are more obvious, so that the
sex of the child may be usually ascertained, along with the position.
For want of proper care the breech has been mistaken for the head, and
face, but this can scarcely happen if the accoucheur is attentive.
It is simply necessary to call to mind what _must_ be felt in each
presentation, as the _nose_ and _mouth_ with the face; the two cheeks
of the posteriors, with the opening between them; and also the
genitals, with the breech; and it can be certainly ascertained which of
these parts are really at the opening. With the knees or feet there can
scarcely be a doubt.
DELIVERY IN A BREECH PRESENTATION IN THE LEFT ANTERIOR SACRO-ILIAC
POSITION.
In this position the legs and thighs are turned up against the
abdomen, the breech in full occupying the passage, with the sacrum to
the left and in front of the mother's pelvis.
The descent of the breech usually takes place without much difficulty,
into the Pelvis, it being small and easily compressed. It descends in
the same direction in which it first presents--that is diagonally, like
the head--and also rotates, or turns round, so that the left buttock
comes in front, just to the right of the pubis, while the right one
goes behind, to the left of the sacrum. The left buttock reaches the
mouth of the Vulva first, in this position, and then remains stationary
there while the right one slides along the curve of the sacrum and
perineum, and passes out first at the lower part of the external
opening. The left however, speedily follows, and when the whole breech
is born it rotates again, one hip coming immediately in front, and
the other going immediately behind. Owing to this movement the long
diameter of the breech is adapted to the long diameter of the Pelvis,
as in the case of the head. This will be evident from the following
Plate:--
[Illustration: PLATE XXXII.
Delivery in a breech presentation, the buttocks having just passed the
Vulva.
_c._ The Coccygis, much straightened.
_p._ The pubic bone, in front.]
The rest of the body then rotates in the same way, and the arms and
shoulders pass through the external opening in the same direction as
the hips. The left shoulder first moves to the right of the pubes,
while the left passes behind; and then, just when they are both passing
out, one comes immediately in front, and the other immediately behind,
placing themselves in the long diameter of the Vulva.
The head passes through the superior strait in the left, anterior
occipital position, and is often delivered in that way; but sometimes
it rotates, and the forehead passes into the curve of the sacrum, while
the occiput is placed behind the pubes. When this occurs the body also
rotates, to accompany the head. This state of the parts is represented
in the following Plate:--
[Illustration: PLATE XXXIII.
Anterior posterior position of the head, the occiput being in front,
after the delivery of the body.
_c._ The Coccygis.
_p._ The pubic bone, in front.]
At this period the head is passed the uterus, and there is therefore
little or no contraction to expel it, so that it often remains a
long time undelivered. It will be seen that the position is very
unfavorable, the longest diameter of the head, the occipito frontal,
being the presenting one, which makes it lie immoveably across. The
means of assisting in such a case are plain enough, the forehead must
be brought down while the body is _raised_, towards the mother's
abdomen; this will throw the top of the head back, towards the sacrum,
and change the presenting diameter. The forehead and bregma rapidly
escape below, and the occiput passes out last. This is the way in which
nature herself also completes the delivery in such cases, when she has
the power.
DELIVERY BY THE BREECH IN THE RIGHT POSTERIOR SACRO ILIAC POSITION.
This position is the reverse of the preceding one, the Sacrum being
behind, and to the right, while the Abdomen is to the left in front.
The same movements are performed as in the first position, and the
whole process is similar, only the reverse way. The Sacrum being behind
however, has to rotate much further to come in front, precisely the
same as with the head when in the posterior position.
The head generally follows the Sacrum, and the occiput comes under the
pubes, as already explained; but sometimes only at the moment when
being disengaged.
DELIVERY BY THE BREECH IN THE FULL POSTERIOR, OR SACRO SACRAL POSITION.
In this position there is no rotation at all, the back of the child
being turned full to the back of the mother, and the whole body,
and head, being expelled in that position. In general there is no
particular difficulty from this position, but on the contrary it is
thought by some to be rather favorable than otherwise. The longest
diameter of the fœtal pelvis, and shoulders, are adapted to the longest
diameter of the mother's pelvis, at the upper strait, and easily pass
it. They will also generally pass the external opening in the same
direction, unless it be very unyielding, or the child very large; and
if they pass the head usually follows, because the parts have been so
much dilated by the passage of the body that they offer but little
resistance.
GENERAL REMARKS ON THE PRESENTATION OF THE LOWER EXTREMITIES.
As a general rule delivery by the breech, or by any other position of
the lower extremities, is less favorable than by the head. The labor is
usually longer, more painful, and more exhausting; still however, it is
generally spontaneous, and not necessarily dangerous to the mother. To
the child, on the contrary, it is dangerous, on many accounts.
It appears, from the observations of M. P. Dubois, that in this
presentation _one child is lost out of every twelve_, while only one
out of _fifty_ is lost in head presentations! The chief cause for this
greater mortality appears to be _the compression of the umbilical
cord_, which is greater, and lasts much longer, than when the head
presents, as will be evident on examining the circumstances under which
delivery is effected in each case. When the head presents it passes,
and also the shoulders, before the umbilicus is reached; the mother's
organs are therefore much dilated, and only the smallest parts of the
fœtus are left, when the cord is engaged in the passage; it cannot
therefore be much compressed, nor for any long time, because the labor
is then soon over. When the lower extremities present this is not the
case, the _smallest_ parts then pass before the umbilicus is reached,
so that the cord has to pass along with the head and shoulders,
which are both the largest and the longest in being delivered. This
compression of the cord stops the circulation of blood between the
fœtus and the Placenta, as will be evident on referring to the
description formerly given of _Fœtal nutrition_; and the stopping of
this circulation is as fatal, to it, as stopping the breath is to an
adult. When the breech presents altogether, there is not so much danger
as with the feet, or knees, because it is large, and in its passage
dilates the parts so much that the rest of the body, and the head,
follow more quickly. There is, of course, no danger till after the hips
have passed, because the cord is not reached before; but the delivery
should be completed as soon after they are born as possible, for every
minute's delay makes the chances for the child's life so much less.