The Natural Mechanism of the 
Expulsion of the Placenta 
-AND THE- 
Proper of the 
Placental Period. 
By GEORGE T. HARRISON, M. A., M. D., 
'Paper read before the Ppew York County 
June 18, 1888. 
[Reprinted from Gaillard's Medical Journal for August, 1888.] 
Horh: 
THE JUDSON PRINTING CO., 
16 Beekman Street. 
1888. The Natural Mechanism of the Expulsion of 
the Placenta 
-AND THE- 
"Proper Management of the Placental Pet iod. 
Paper read before the N. Y. County Medical Association, June 18, 1888. 
GEORGE T. HARRISON, M. A„ M. D. 
The subject to which I ask your attention this evening may seem 
to some among you, at first thought, either of slight importance, or 
else so completely exhausted that further comment is unnecessary and 
superfluous. A moment's reflection, however, will, I think, convince 
you that such a judgment is far from the truth. In a paper read to 
the Obstetrical Society of Edinburgh, in 1871, on the expulsion of the 
placenta, Dr. Matthews Duncan uses the following language: " No 
one will dare to say it is unimportant; for there is no truth in nature 
which, however insignificant it may appear, has not even now, or may 
not have in future, bearings upon practical rules which may be of 
value to the obstetrician." Playfair, in his excellent treatise on the 
science and art of midwifery, declares in reference to the management 
of the third stage of labor: "There is unquestionably no period of 
labor where skilled management is more important, and none in which 
mistakes are more frequently made." In Germany, within the last few 
years, a most animated controversy has been in progress upon this 
theme, as the result of which much valuable material has been ac- 
cumulated, of great help in explaining the physiology of the placental 
delivery and, as a corollary, in laying down the principles which should 2 
guide us in the management of the placental period. There are still 
moot points, however, and consequently this may still be considered 
one of the burning questions of the day. After the Crede method had 
been adopted by obstetricians in Germany for a quarter of a century, 
and subsequently had won its way into general use throughout the 
civilized world, the attention of the medical profession was arrested in 
1880 by a publication of Dohrn, in which this author took ground 
against the active intervention involved in the method of Crede, and 
insisted upon the adoption of an expectant plan of treatment. Ahlfeld 
followed him in successive publications, and on the basis of large clini- 
cal experience combated the Crede procedure, charging it with pro- 
ducing a greater loss of blood than would ensue if the expectant plan 
were wholly or in part adopted ; and, secondly, holding it responsible 
for the retention in the uterine cavity of remnants of decidua and 
chorion to a greater or less degree. And for this writer the retention 
of such membranes in the cavity of the uterus is often productive of 
the most disastrous consequences to the puerperal woman. The late 
Carl Schroeder, in association with his pupils, Hofmeier, Ruge and 
Stratz, recently studied the physiology of the placental period most 
carefully, and here, as in so many other directions, we owe a deep 
debt of gratitude to the Berlin school. So late as the year 1883, Ahl- 
feld* could complain " that it is certainly a striking phenomenon that 
the physiological process of the detachment and expulsion of the pla- 
centa has remained hitherto almost unknown." . . . " The single 
attempt to answer the questions here to be solved by a large number 
of investigations on the living object were made by Lemser in the year 
1865, and this work was only lately appreciated." The studies of 
Schultze and Matthews Duncan upon the mechanism of the expulsion 
of the placenta, if not fulfilling the conditions laid down by Ahlfeld, 
have yet shed much light upon this subject and will first be con- 
sidered, and then certain problems be touched upon belonging here. 
Only those among you whose duties as active practitioners have 
not allowed you the leisure requisite to keep you informed upon the 
recent investigations in regard to the physiology of birth, I wish to 
make the explanatory statement that in labor the uterus is differen- 
tiated into an active contracting upper portion, the uterine body, and a 
lower passive, flabby uterine segment and cervix, the separation be- 
tween the active and passive parts being defined by " the ring of con- 
traction." The importance of this division will immediately appear. 
After the expulsion of the child the placenta arches into the uterine 
* JJerichte u. Arbeiten. 3 
cavity, forming marked torosities, so that blood accumulates between 
it and the uterine wall. The completely detached placenta gradually 
descends into the ring of contraction, presenting its foetal surface, 
and in its descent inverting and detaching the membranes of the 
ovum, until it attains to the space formed by " the lower uterine seg- 
ment " and cervical cavity. The placenta lies in this space, folded 
upon its uterine surface, and between these folds a coagulum of blood 
is contained. This mode of the delivery of the placenta is that de- 
scribed by Schultze. Matthews Duncan maintains, however that it is 
observed because the natural mechanism is interfered with. He in- 
sists that the placenta Comes edgeways, its uterine surface gliding 
along the surface of the uterus; that its foldings, parallel to the length 
of the maternal passages, are well squeezed together, and that little 
space is offered for the reception of blood flowing from the uterine 
sinuses. The uterine wall keeps close to the folded placenta. Ac- 
cording to him, in the natural mechanism there is no haemorrhage 
worthy of the name. I am convinced from my clinical observations 
that the mechanism described by Schultze is the usual one, and that 
what Duncan calls the normal is the exceptional mechanism. Let us 
now consider some of the facts which modern investigation has 
elicited in reference to the anatomy and physiology of placental de- 
tachment. 
Possessing as we do numerous anatomical studies upon the struct- 
ure and attachment of the placenta, it is nevertheless a fact that none 
of them furnish us an anatomical basis on which to construct a theory 
competent to explain satisfactorily the process by which placental de- 
tachment is effected. An exception, however, must be made in favor 
of the researches of C. Ruge, which undoubtedly help us to a clearer 
understanding of this process. According to this author,* the follow- 
ing are the microscopical appearances of the zone of attachment of 
the placenta to the parturient uterus. In consequence of the displace- 
ment of the placenta on its place of attachment, called forth by its in- 
ability to contract in contrast with the latter, a relaxation begins very 
soon in the decidua serotina, without, however, going so far as to pro- 
duce separation. Cords of attachment are formed, to a certain ex- 
tent, which render it possible for the placenta to follow the contracting 
surface of the attachment. A species of network of connective tissue 
is developed which is susceptible of extensive displacement. The con- 
nective tissue bands constituting the meshes of this network contain 
vessels which effect the exchange of gas between maternal and foetal 
* Der Schwongere und Kreessende Uterus, Bonn, 1886. 4 
placenta. This phenomenon furnishes an explanation of the fact that, 
in spite of the long task of parturition, in spite of frequent labor pains, 
and notwithstanding retraction of the uterine body, however fully de- 
veloped, the foetal circulation is not disturbed. As a consequence of 
the uterine contractions, a locus minoris resistentiae is created from 
the beginning in the placenta, in which also the complete detachment 
takes place later on. This place is not united to a definite layer of 
the decidua, but is developed accidentally, sometimes higher, some- 
times deeper. In the very beginning of labor, with the first regular 
pains this phenomenon commences, and the relaxation becomes more 
complete the longer their duration. It is plain that the effect of the 
displacement of placenta and uterine wall will be exhibited more in 
the centre than at the edge, where the attachment is closer. Ruge 
demonstrated the network developing in the decidua serotina both on 
the placenta in situ and on had been delivered, and 
showed that just here the separation had taken place. That in spite 
of the most energetic pains, only this laxity is effected lies in the be- 
havior of the placental place itself. It does not follow the remainder 
of the uterus in the contractions, and always remains thinner, because 
the placenta is pressed against it in consequence of the increased intra- 
uterine pressure during " the pain." The contraction and retraction 
of the muscular tissue is here more incomplete and does not take place 
so quickly, and instead of the interwoven and shortened condition of 
this tissue, as we find it under other circumstances, we see here the 
saw-like and wavy arrangement longest stamped. As, consequently, 
the place of attachment does not diminish so energetically in all direc- 
tions as would suffice for the detachment of the placenta, considering its 
inability to contract, it is rendered possible for the latter, in view of 
the fact that it becomes thicker, that its foetal surface shows projections 
and furrows, and that its edges protrude widely beyond the place of at- 
tachment, to preserve its cohesion with the uterus. 
From these researches it will be seen that the detachment of the 
placenta is histologically pre-arranged during parturition up to the 
moment when the child has left the maternal parturient canal. An 
important question now confronts us : Does the change in the size of 
the uterus, appearing immediately after the birth of the child, suffice 
for the detachment of the placenta, or are several independent contrac- 
tions necessary ? As Barbour observes, there are three ways of de- 
tachment. The separation of the placenta is either : 
i. The result of the change in the size of the placental place after 
the evacuation of the uterus ; or 5 
2. The consequence of the haemorrhage or escape of serum behind 
the placenta; or 
3. The result of uterine contractions and of the endeavor on the 
part of the uterus to expel the foreign body. 
Barbour decides in favor of the latter mechanism. Ahlfeld, from 
the result of his studies, arrives at the conclusion that " the reduction 
in the surface of the place of attachment of the placenta is the most 
important factor for its detachment. Since a detachment of the edge 
in the first stages cannot, as a rule, ensue, the central part becomes 
separated. The space formed is filled with blood by aspiration." 
From the observations of E. Cohn, of Berlin, to whose excellent paper 
on this theme I beg to acknowledge my indebtedness, it is singly and 
alone the " pains " belonging to the placental period which effect the 
detachment of the placenta. " The first uterine contraction of the pla- 
cental period," says this author, " has the most important effect, 
whether it appears at the time the child leaves the maternal genital 
canal, or not until after some time of repose. It effects the detach- 
ment which had already during parturition been for the greatest part 
preliminarily prepared, and facilitates the formation of the retro- 
placental effusion of blood, which is the second important factor." 
And here I would remark that the exposition of this theme by Barnes, 
as found in his excellent text-book, partakes too much of metaphysical 
reasoning, and consequently his views rest rather upon subjective im- 
pressions than objective demonstration. The effect of the second 
uterine contraction is twofold. The placenta is now, mainly by the 
blood effusion, completely separated up to the insertion of the mem- 
branes of the ovum, and yielding to the pressure produced by the 
uterine contraction, it will make ready to leave the uterine body. This 
extrusion is completed by the following uterine contractions, aided 
by the natural weight of the placenta itself. The placenta, with the 
centre of the foetal surface presenting, now passes through " the ring 
of contraction " into " the lower uterine segment," where it makes room 
for itself by passive distension. 
As soon as the placenta is detached the placental area is contracted 
by contraction and retraction of the muscular tissue to such a degree, 
that the vessels coursing in it are occluded or very much narrowed ; on 
the other side the retro-placental blood usually coagulates so rapidly 
that, as a consequence, there is a quick thrombosis of the lacerated 
vessels. Let us note now the behavior of the uterine body as observed 
through the abdominal coverings. 
With each uterine contraction the fundus ascends higher and 6 
higher, the body becomes smaller and narrower, and the "ring of con- 
traction " which had disappeared immediately after the birth of the 
child, again becomes very plainly marked-consequently the most cer- 
tain clinical symptom of the detachment and extrusion from the 
uterine body of the placenta is the ascent of the fundus uteri, the 
diminution of its size, the manifestation of the furrow corresponding to 
"the ring of contraction," and "the lower uterine segment" dist- 
ended by the extruded placenta. This detachment of the placenta 
from the uterine wall and its extrusion into the lower uterine segment 
occurs almost without exception without external aid. Consequently 
it may be logically inferred that, leaving out of the question patholog- 
ical cases, the natural forces are fully adequate to effect the detach- 
ment of the placenta, and that there is no necessity of any sort of 
active intervention on the part of the obstetrician to assist this physi- 
ological act. Having in view the physiological facts just discussed, 
what it may now be asked is the best method of managing the placen- 
tal period. Four methods may be enumerated as having advocates 
among distinguished obstetricians. First is the method of Crede, which 
is the one most generally adopted, the essential feature of which is that 
the placenta is manually expressed out of the uterine body. Secondly, 
the Dublin method described by McClintock and Hardy in 1848, and 
afterwards by Barnes and Spiegelberg. 
This manipulative procedure consists in this, that immediately after 
the exit of the child's head through the vulva, the hand is laid on the 
fundus and by friction and kneading energetic contractions are evoked, 
so that the placenta is quickly separated and is expressed beneath 
" the ring of contraction." By further pressure it is forced out of the 
vulva. Thirdly, by the expectant method which has Ahlfeld, Dohrn 
and Freund as its advocates, the separation and Xatrusion of the pla- 
centa is left, as a rule, to the natural forces. Fourthly, the method of 
Schroeder-which I give in his own language: " I consider it the best 
procedure in the placental period, after the expulsion of the child, not 
to rub or press the uterus, but to wait quietly until the diminution and 
ascent of the uterine body and the protuberance above the symphysis 
indicate that the placenta is expelled from the uterine cavity, then by 
gentle pressure to expedite its passage through the vulva." The ob- 
servations of Cohn show that the spontaneous expulsion of the pla- 
centa out ot the uterine cavity into the " lower uterine segment" re- 
quires for its completion five to fifteen minutes. After this is accom- 
plished, further delay is unnecessary, as the placenta can be removed 
now without injury, and left alone, might remain undelivered hours, 7 
nay, for days. The manipulation which Schroeder employed was to 
place the side of the hand in the furrow underneath the uterine body 
and then to exert a general pressure downward. As this procedure re- 
quires a good deal of practice and skill, Schroeder recommended sub- 
sequently the gentle pressure of the fundus uteri down into the superior 
strait. As Cohn remarks, the contracted uterine body acts like the pis- 
ton of a syringe, which drives everything movable in front of it. This 
method of Schroeder I have found perfectly satisfactory in practice, 
and would urgently recommend its general adoption. The method of 
Crede I would reserve for the cases in which the placenta does not be- 
come detached, or those in which it has been separated in the way de- 
scribed by Duncan, and consequently has remained with the upper 
edge fixed in the uterine body. When there is some obstacle which 
prevents the placenta from escaping completely out of the uterine 
body, as for example, might occur when a very large placenta had to 
pass through a moderately contracted " ring of contraction," this 
method would be indicated. I concur entirely in the views expressed 
by Crede in regard to the innocuousness of the membranes of the 
ovum and decidua when retained in the uterine cavity, provided the 
conduct of the labor has been aseptic. Says this distinguished obstet- 
rician : " I might mention again the fact that in the last four years 
(ist of January, 1883, to 31st March, 1887), no regard whatever inten- 
tionally, was paid to the frequent occurrence of retained remnants of 
ovum and decidua in 4,969 births which took place in the Leipzig 
Clinic and Polyclinic, and that no single puerperal woman died of this 
treatment of omission or was even very sick, and only slight disturb- 
ances occured in the uterine secretion (bad odor, moderate, transitory, 
elevations of temperature, a matter of indifference, the general condi- 
tion being otherwise good). ... If we leave the womb at rest 
with its contents of remnants of the ovum, no disease of any sort of 
significance follows, to say nothing of a case of death."* The views I 
have here advocated I believe rest on a firm physiological basis, and 
with that conviction would commend them to your earnest considera- 
tion. 
* Archiv. fur Gynaekologie, B'd. XXXII. lift. I.