PRESENTATIONS AND POSITIONS OF THE FŒTUS.
The child may present several different parts of its body, at the
commencement of delivery, and they may be in different positions
relatively to the different parts of the Pelvis. All these require to
be known.
Different authors have made different classifications of the
presentations and positions, and have differently named them; but this
is of little consequence, since they are still the same, no matter how
they are named. I shall follow the arrangement of M. Chailly, because I
think it equally perfect, and much more simple and practical, than any
other yet proposed.
PRESENTATIONS.
The fœtus may present at the mouth of the Womb either by the _head_,
the most usual way--by the lower extremities, which is the most
frequent way after the head--or by various parts of the trunk, which is
the least frequent way of all.
In each of these _three_ full presentations there may be certain
variations, which require to be noticed. The head, for instance, may
present either by the _cranium_ or by the _face_; the lower part of the
body may present either by the _feet_, the _knees_, or the _breech_,
according as the legs and thighs are flexed or extended; and the trunk
may present either on the _right_ or _left_ side, and inclined towards
the _back_ or towards the _chest_, though neither the back nor abdomen
ever fully present.
Each of these variations may also have slight variations again. Thus
the face may present full, or by one or the other cheek, and so on.
These variations however, are of little practical consequence, because
we only find them at the very commencement of the labor, and they
always change to the full presentation.
Practically speaking therefore, there are _five full presentations_,
viz., _the Cranium_, _the Face_, _the Breech_, _the Feet_, or knees,
and the _Trunk_, either by the right or left side.
The _varieties_ of these, as already remarked, not requiring any
special attention from the accoucheur, providing he is not puzzled or
misled by them.
POSITIONS.
The position means the particular direction in which the presenting
part of the Fœtus is placed in relation to the Pelvic straits. The
Pelvis itself is supposed to be divided into two similar halves, the
_right_ and the _left_, and each presenting part has one particular
place which is referred to as the indicating point. Thus, for
instance, in the Cranium the Occipit, or behind part of the head, is
the indicating point; and we therefore say, in Cranium presentations,
that it is a _right or left Occipital position_, according as the
back of the head is to the right or left side of the Pelvis. In face
presentations, the chin (_mentor_) is the indicating point, and we
therefore say it is a _right or left mento position_, according as the
chin is towards the right or left side. In breech presentations, the
child's sacrum is the indicating point, and we then say it is a _right
or left sacral position_, according as the Sacrum is towards the right
or left side of the Pelvis. In trunk presentations, which are always
crosswise, the head (cephalo) is the indicating point, and we therefore
say it is a _right or left cephalo position_, according as the head
lies towards the right or left side of the mother's body.
In Cranium presentations also, the back of the head is not merely on
the right or left side, but may be at two different points on each
side. It may be either nearest to the Sacrum (posterior), or nearest
to the pubes (anterior), but still against the Ilium; it is therefore
called a _right or left anterior_, _or posterior_, _occipito iliac
position_, as the case may be. Sometimes also, the occiput lodges
immediately on the pubis, instead of going to either side, and that is
called an _occipito pubic position_; at other times, on the contrary,
it is placed against the Sacrum, instead of being on either side, and
that is called an _occipito sacral position_.
In presentations of the head therefore, we may reckon _six_
positions--the right and left anterior and posterior occipito iliac,
and the pubic and sacral.
In presentations of the face the same; they being _mento_ iliac and so
on, instead of occipito.
In presentations of the lower extremities also the same, excepting that
they are _sacro_ iliac and so on, instead of occipito.
In presentations of the trunk we have but two positions for each side,
the right and left cephalo iliac; according as the head is on the
right or left side of the mother's body. The child always lying, in
presentations of the trunk, crosswise--the feet on one side and the
head on the other.
Most authors enumerate many more presentations and positions, but they
are of little practical utility. When the head presents, for instance,
the delivery takes place in nearly the same manner, let it be in what
position it may. And in presentations of the face, or of the lower
extremities, the particular position is of little consequence, the
delivery being usually effected much the same in them all. Some of
the positions are, it is true, much more favorable than others, but a
spontaneous delivery, generally speaking, occurs in all of them, when
the head, face, or lower extremities presents. Very frequently indeed,
the less favorable positions are changed to the more favorable ones,
and the worst seldom do more than impede delivery for a time, unless
there be some malformation, or loss of power. I therefore refer to them
more for convenience in future explanations, and to enable my readers
to know what is meant by them, when they read other books; not because
they are really necessary to be understood, or of any great practical
use.
The celebrated Baudelocque admitted _seventy-four positions_, and
_twenty-two presentations_; and the number might be made still greater,
if all the variations were to be enumerated. Such classifications
however, are more ingenious than useful, and they are but little
noticed even by medical men.
I shall merely describe the mechanism of labor in the most frequent
positions, in each presentation, because the others usually change
into these; and even when they do not, the process of delivery is
essentially the same, and also the mode of assisting it.
MODE OF ASCERTAINING THE PRESENTATION AND POSITION.
_The Presentation._--Although in general it is not possible to
ascertain with certainty, what part of the fœtus presents to the
mouth of the Womb, until labor commences, yet a tolerable judgment
can frequently be formed before. In head presentations, on performing
ballotment, the head is felt, like a firm round tumor, occupying all
the space which the finger can reach, very differently from any other
part. The peculiar cramps in the female's lower limbs, and frequent
inclination to urinate, mentioned in the signs of labor, are also
strong indications of this presentation, being seldom experienced in
any other. When the labor has actually commenced there can be but
little uncertainty in these cases, for, immediately the mouth of the
Womb is sufficiently open, the finger can be introduced, and the head
felt like a smooth, round, and elastic bony tumor, not likely to be
mistaken for anything else, if ordinary care be taken. After the waters
have escaped, it can of course be felt still more distinctly. If even
an inexperienced person bears in mind the _shape_ of the head, and
reflects how it must _fill up_ the passage, and how it must feel, from
being composed of separated thin bony plates, lying on a soft yielding
substance like the brain, he can scarcely fail to recognize it. The
sensation is very much like that of pressing a piece of firm card board
on an inflated bladder, which forms a tolerable representative of the
fœtal head. Sometimes there is a difficulty from a great quantity
of water being intruded between the membranes and the head, which
somewhat obscures the touch, but this only necessitates greater care.
The water however, may be in such quantity as to entirely prevent the
touch, in which case nothing can be done till the membranes break; the
presentation can then be ascertained with certainty, and it will be
quite early enough to render assistance, if it should be an unfavorable
one. I have known some inexperienced persons mistake the bag of water
itself for the head, and commit great errors in consequence.
The Face can seldom be mistaken, because the nose, or mouth, may be
felt; and, by passing the finger up the side of the head, the ears also.
The trunk is in general easy of recognition. Nearly always the right
or left shoulder occupies the passage, or is near to it, so that the
finger may be readily passed under the arm pit. The shoulder joints,
the ribs, or the shoulder blade bone, all feel very different to the
head, and are not likely to be taken for it.
In presentations of the lower extremities there is still less danger of
error. If the feet, or knees, occupy the passage, they can scarcely be
mistaken. The breech is certainly something like the head in its form,
but feels different, and is divided down the middle by the indentation
between the two cheeks, along which the finger can be passed till it
enters between the limbs.
In irregular presentations, as of the arms for instance, or of one
leg, or an arm and leg, it is only necessary to carefully feel them,
so as to ascertain their form, and the relation of their parts. Thus
the fingers can be distinguished from the toes, and the feet from the
hands, particularly if the ankle can be felt.
The accoucheur should ascertain the particular presentation _as early
as possible_, because he may sometimes be of service in correcting
an unfavorable one, if he is certain of it in time, and knows what he
is about. He should not however, use any degree of force to ascertain
it, in case he cannot do so without, but wait till the conditions are
more favorable. Neither should he, with the same object, rupture the
membranes too soon, for he may thereby cause considerable delay and
difficulty, without any good to counterbalance it.
All the above-named presentations may, and usually do, terminate
spontaneously, except those of the trunk, and even they do
occasionally, though more frequently they require assistance.
_Relative frequency of the different presentations._--The most
favorable presentations, and positions also, are always the most
frequent, while the unfavorable ones are but seldom met with.
According to Madame Lachapelle, in _fifteen thousand six hundred and
fifty-two labors_ there are about _fourteen thousand seven hundred
and forty-nine_ presentations of the head and face; about _five
hundred and eighty-six_ of the breech, knees, and feet; and only about
_sixty-eight_ of the trunk, or shoulders.
_Positions._--The position is generally of but little consequence,
because in all the favorable presentations spontaneous delivery occurs
in every position alike, and in the unfavorable presentations the same
assistance is required in one position as in another. In some cases an
unfavorable position of the head may be changed however, to a better
one; and therefore, so far as the head is concerned, the positions are
worth ascertaining.
The mode of determining the position is by feeling for the _sutures_
and _fontanelles_, described in Chapter VIII; and this cannot be
usually done till after the membranes are broken, when the head can be
distinctly touched. By referring to Plate XXIV, the shape and position
of the Fontanelles will be seen, and if the head be supposed placed
with the top downwards, and the back of it to the mother's left side,
they may be readily found with the finger.
In the left anterior occipito iliac position, or that when the back
of the child's head is against the left side of the mother's pelvis,
and nearest the pubes, while its forehead is against the right side,
and nearest the sacrum,--the sagittal suture, or opening along the
top, will of course run across from right to left. This opening may
be distinctly felt with the finger, which should be passed along
it towards the right side, and it will then reach the _anterior
fontanelle_; afterwards it should also be passed to the left side, and
then it will reach the _posterior fontanelle_. The difference between
these two openings, in shape and size, is shown in Plate XXIV, and even
if a person has never seen, or felt, the head of a newborn child, they
can scarcely be taken for each other, after noticing that Plate.
If the anterior fontanelle should be felt on the left side instead
of the right, and near the pubes, while the posterior fontanelles is
to the right, and near the sacrum, the position must be the _right
posterior occipito iliac_, or just the reverse of the former.
If the sagittal suture should be found to run across from the pubes
to the sacrum, instead of from one side to the other, it will then
indicate either an occipito pubic, or occipito sacral position,
according as the back of the head is behind or before; and this can be
readily ascertained by finding either of the fontanelles.
In short, if the relative position, forms, and directions of these
openings in the child's head be clearly understood, the position of
the head can nearly always be determined by feeling them, as will be
evident by referring to our former explanation of them.
Sometimes however, the bones overlap a good deal, from the head being
pressed, and then instead of an opening along the top, a _seam_ will be
felt. And sometimes, from long continued pressure, a quantity of blood,
and watery fluid, will be effused under the scalp, so as to prevent
the bone being distinctly touched. But these accidents seldom happen,
and with ordinary care and perseverance, need not prevent the position
being determined, after a little delay.
The position of other presenting parts is easily ascertained, by
feeling for some known point--as the _nose_, or the face, the
depression between the cheeks, or the breech, and so on.
_Relative frequency of the different positions._--The most favorable
positions, like the most favorable presentations, are also the most
frequent. According to Baudelocque, in _ten thousand three hundred and
twenty-two cases_, of head presentation, there were _eight thousand
five hundred and twenty-two_ cases when the back of the child's head
was on the mother's left side, and towards the front, (or in the left
anterior occipito iliac position); _one thousand seven hundred and
fifty-four_ when it was on the _right_ side towards the front, (right
anterior occipito iliac); _twenty-five times_ to the right side, but
towards the Sacrum, (right posterior occipito iliac); and _nineteen
times_ on the left, but towards the Sacrum, (left posterior occipito
iliac.) Being most frequently with the back of the head _towards the
front on the left side_, as shown in Plate XXVII; next towards the
front on the right side; and but seldom towards the Sacrum, or back,
on either side. In all these ten thousand cases we do not find a
single instance of the head lying from back to front, in the _occipito
pubic_, or _occipito sacral_ positions, commonly called transverse;
neither do we find a single instance in _fifteen thousand six hundred
and fifty-two cases_ recorded by Madame Lachapelle; which will show
how rare such unfortunate positions must be. What this great frequency
of one particular position depends upon we do not know--possibly on
that cause, previously alluded to, which determines the most frequent
presentation.
In the next Chapter, the mechanism of delivery, or the manner in which
the child escapes out of the body, as it most frequently occurs, will
be fully explained.