Pathological Anatomy.—Placenta prtevia differs from the normally in serted placenta in its form, as well as in the character of its tissue. While the latter has an average weight of between 161 and 20 ounces, a thick ness of an inch, and measures about 71- inches in its greatest diameter, the former at term weighs hardly 161 ounces, and does not exceed 1 • inches in thickness. In most cases, a placenta prEevia is extremely thin, and is elongated rather than oval in shape. The portion which presents is often dark red, and is thus distinguished from the rest of the placenta, which is pale and anaemic. As the placenta approaches the os the villi become small and scattered, and the portion corresponding to the cervix, or its vicinity, is the softest of all. It is not rare to see part of it trans formed into connective-tissue, or undergoing fatty degeneration, whence arise isolated cotyledons (placenta succenturiata); or it may spread out in such a way as to cover nearly the whole of the internal surface of the uterus. On examining the placenta, we usually find the cotyledons at the edge of the os flattened, and the placental tissue reduced to a sort of lamella, and heaped upon itself, as it were; under the microscope we rec ognize fibrous metamorphosis and fatty degeneration of the cells of the villi. Apoplectic spots are frequently seen. The cord has usually a cen tral, often a marginal insertion. Gendrin describes the changes in the placenta as consisting of a general softening of the tissue and its conver sion into a homogeneous, reddish mass, which resembles the dependent portion of a congested lung, but is as fragile as the spleen. This change takes place when hemorrhage has occurred some time before, or during, parturition. In the zone adjacent to the central portion the placental tis sue is condensed and is reduced to a dense, granular, homogeneous mass, of a yellow color, very fragile, and traversed by whitish filaments. In the midst of the tissue are small clots, which are intimately connected with the surrounding substance. The surface of the placenta, over the portions thus altered, often presents numbers of small, white spots, slight ly projecting, and resembling at first sight tubercles on the peritoneum in tuberculous peritonitis. The zone external to the one just described pre sents a reddish tissue, in which is blood that has become coagulated and even incorporated with the placental tissue; this tissue itself is much *softer and more friable than normal. The appearances differ according to the age of the changes, those near the centre of the placenta being most ancient and corresponding to the early hemorrhages. Aside from these alterations, lesions are produced in the placenta at the moment of expulsion; these appear as lacerations filled with coagulated blood, the ruptures radiating from a central point, as when a fragile body is crushed in the hand.
reports 813 cases of placenta prasvia among 876,432 cases of confinement (1 to 1078), the greatest number occurring in patients between the ages of 30 and 35, the smallest between 13 and 19. 1347 out of 1574 women (observed by various authors) were multiparte; among 691 cases collected by Muller, 134 were primiparfe, 114 II-parEe, 70 III-parze, 78 IV-paree, 54 V-parse, 42 VI-parte, 48 VII-parte; 24 XI-parse, 6 XIII-parw.
etc. In general, causes that induce enlargement of the uterus favor ab normal implantation.
Various explanations are offered to account for cervical implantation, such as the mobility of the uterus, the position of the woman during fecundation, the weight of the ovum (!), obliquity of the uterus, etc.
Some affirm that the decidua developes at such a point in the cavity, that the ovule is attached abnormally when it reaches the cavity. Carmichael thinks that the placenta may become displaced from its normal position, through the general expansion of the uterus, and be pushed downwards and backwards. Schroeder admits that increased size of the uterine car ity, and an abnormally smooth condition of the mucosa, may favor abnor mal insertion; increase in size is most frequent in multiparEe, smoothness of the lining membrane is produced by previous leucorrhceal discharges.
Symptoms.—They almost never appear before the sixth or seventh month. Nearly all authorities agree on this point, that a hemorrhage which appears for the first time at this period, depends almost invariably on abnormal insertion, and, according to Naegeli.., it begins so much the sooner, according as the placenta covers the os more or less completely. When the implantation is marginal, hemorrhage may not occur until the end of pregnancy, or even the beginning of labor. Among 1,121 cases hemorrhage took place before the sixth month in 34, between the sixth and seventh in 53, during labor in upwards of 73. This hemorrhage ap pears suddenly, without previous symptoms, often during the night, when the patient is asleep or perfectly quiet. Rarely she has colicky pains, or a feeling of discomfort in the loins for a few moments before the flow. The hemorrhage is always external, beginning gradually, and soon becom ing more profuse, until a large amount is lost. It soon ceases, as it be gan, without apparent cause. The blood has sometimes a venous, some• times an arterial hue, and has a marked tendency to coagulate. The flow ceases and may not return for from eight to fifteen days, or even longer; the patients have no special symptoms during the interval; then another hemorrhage occurs, as in the first instance, without appreciable cause, but more profuse and continuous than before. These phenomena may be repeated until labor begins, when the bleeding becomes so extensive as to place the woman's life in real danger. Intermittence is the distinguish ing characteristic of the hemorrhage; anaemia, swelling of the face, gene ral ("demi, attacks of syncope, sometimes chills, fever and convulsions are accompanying symptoms. The blood may collect to some extent in the interior of the uterus, but it is essentially external in character. Bal lottement is absent in cases of placenta prsevia, as the inferior segment is so much thickened by reason of the attachment of the placenta to it that the finger can not reach the foetal part. The presentation is often faulty. Thus Simpson records 21 transverse presentations among 90 cases of pla centa prwvia, and Muller 272 among 1148.
When labor begins and the cervix is sufficiently dilated to allow the finger to be inserted, the diagnosis is no longer doubtful. We feel at once the thick, rugoso membranes, or even the edge of the placenta, easily recognized by its lobes and irregularities; great gentleness should be used during the examination, for fear of increasing the hemorrhage. Another sign is only observed after labor has begun, viz. : In accidental hemor rhage the flow always stops during the contraction, but in abnormal in sertion, on the contrary, it continues in the interval between the contrac tions, and increases during each pain, as long as the membranes aro intact.