The changes, local and general, resulting from the physiological state of pregnancy are extremely variable, often approximating or simulating pathological conditions, so that we must differentiate and discriminate between such as pertain to the normal condition and such as indicate pathological changes and threatening danger. This is necessary, as prevention is, above all, important, it being often possible thus to save two lives with by far less danger and suffering to the mother than is to be expected from the treatment of abortion once inaugurated after the time of possible prevention has passed. Moreover, a correct post-abortum diagnosis is important for the future welfare of the patient, if not from a medico-legal point of view; and this is equally impossible without a knowledge of the physiological condition. This will enable us to determine whether the ovum expelled is healthy or not—whether the causes are traumatic or criminal, or whether the abortion is due to pathological changes; which, again, must guide us in treatment.
Abortion is the expulsion of an ovum the product of a conception, and can only occur during the period of menstrual life, as conception, the impregnation of the female ovule by the male semen, is the consequence of fruitful intercourse, liable to take place at any time during the period of womanhood, the thirty years of female menstrual life from puberty—the appearance of the catamenia—to the time of their cessation. Its occurrence is followed by intense physiological activity of the maternal organism, lasting throughout gestation to the time of its natural termination with the expulsion of the fully-developed ovum at term at the end of the tenth lunar month. This is made evident by striking changes in the entire system, but especially in the sexual organs, which in the earlier period of pregnancy are entirely progressive, developmental, whilst in the later months, toward term, the character is changed to that of a retrograde metamorphosis, preparatory to the separation and expulsion of the ovum and final restitution of the organs. This hyper-activity inaugurated by impregnation becomes evident by marked changes in the system of the mother, in the sexual organs, and in the ovum itself.
Changes in the Maternal System.—These are most peculiar and varied, differing in repeated pregnancies in the same patient, sometimes entirely absent, at others most distressing, even fatal; sometimes appearing at one period, sometimes at another. Healthy, robust women may suffer throughout the entire period of gestation, whilst those at other times ailing are well only in this condition. The most marked of these symptoms are the hystero-neuroses, disturbances of the entire nervous system, central and peripheral; mental depression, more rarely excitement; gastric disturbances, nausea and vomiting; increased activity, renal and pulmonary, consequent upon changes in the circulation; discoloration of the skin upon the forehead, the linea alba, and areola; oedema and varicosities of the veins upon the lower extremities. All these, and many others still more erratic, may accompany the normal physiological condition.
Changes in the Uterus and Pelvic Viscera.—Whilst the ovum develops in the uterus, this organ, its appendages, and the viscera surrounding it, enclosed together within the pelvic cavity, undergo the most marked changes. The early months of pregnancy are those of greatest physiological activity in the uterine muscle, the period of its hypertrophy. This is inaugurated from the very moment of conception, at first increasing, then gradually lessening, until within the last months, when it becomes passive, the rapidly-growing ovum merely distending the hypertrophied uterus, apparently increasing in size, but merely distended by its contents, as a rubber bag would be. In the earlier months the growth of the uterus is entirely due to muscular development—after the fifth month to distension. The individual muscular cells attain enormous growth, and a large number of pre-existing embryonic cells are developed; so also in the interlacing connective tissue. The blood-vessels as well as the lymphatics increase in size and length; the arteries become tortuous; the capillary circulation is to a great extent supplanted by sinuses.
Weighing in its normal condition, when at rest, little above an ounce, the uterus attains within the first four or five months a weight almost fifteen times greater. Remaining the first four months within the pelvic cavity, the increase in size is not of that diagnostic importance which it attains in the later months, when it is to be felt beneath the abdominal walls, though at the end of this period it is distinctly perceived above the symphysis; about the fifth month, between navel and symphysis; and at the sixth month, at the height of the navel. At the end of the third month the uterus is some 4½ to 5 inches in length, by 4 in breadth and 3 in thickness; at the end of the fourth month, 5½ to 6 inches in length, by 5 in breadth and 4 in thickness; at the end of the fifth month, 6 to 7 inches in length, 5½ in breadth, and 5 in thickness; at the end of the sixth month it is some 8 to 9 inches in length.
The changes which take place in the cervix are a merely passive accompaniment of the uterine hypertrophy, it being enlarged more especially by reason of the succulence of its tissues consequent upon the congestion and activity of the body. It is somewhat enlarged in all its dimensions, thickened, and elongated, soft, velvety to the touch, appearing, however, somewhat shortened by reason of the hypertrophy of the vaginal attachment—a condition that approximates rather that of the vagina and external sexual organs than that of the uterus, softened, succulent, somewhat hypertrophied, congested, of a deeper bluish-red wine color, its cavity occluded by thick tenacious mucus, as the secretions of the mucous membrane of the vagina and external sexual organs are also augmented. In the first and second months the uterus is retroverted, the cervix seems to descend as the enlarged organ, by reason of its weight, settles in the pelvis, the fundus sinking down in the hollow of the sacrum, the cervix consequently pointing more forward; as the organ increases in size and rises above the brim in its endeavor to escape the confining space of the pelvic cavity, the enlarged fundus, meeting with the resistance of the promontory, seeks the point of least resistance, and the uterus begins to assume that position of anteversion which continues to become more marked as pregnancy progresses: the cervix points backward into the hollow of the sacrum, and rises gradually (as the fundus increases in size and withdraws from the pelvic cavity).
The Uterine Mucosa.—This structure is as interesting as it is important. The wonderful changes which it undergoes go hand in hand with the various changes and stages of female life: it is the nidus for the reception of the impregnated ovum; it serves to shelter and nourish the delicate ovum, and if diseased, affording insufficient nutrition, leads to the death and expulsion of the embryo. Its shreds when expelled are of diagnostic importance, and in early abortions its massive thick tissues, changed by disease, often cause greater trouble than the ovum itself, forming, alone or with the membranes proper of the ovum, what is so commonly but erroneously called the placenta in abortion. The membrane which lines the cavity proper of the uterus, passing at the internal os into the mucous membrane of the cervical canal, is characterized by the absence of even the slightest trace of submucous or areolar tissue—by its peculiar substratum of connective tissue abounding in cells and tubular glands. It is closely and inseparably attached to the muscular coat. In a state of rest it is a little over 0.04 inch in thickness at the fundus,2 and the anterior and posterior walls diminishing toward the sides, the cervical and tuber ostea. It is traversed by a series of tubular glands, wavy in their upper part, bifurcated toward their base, running more or less parallel to each other. In this membrane, so important for the preservation and development of the ovum, the physiological activity of the system is inaugurated, and seems to centre during the first week of gestation. With the impregnation of the ovule the uterine mucosa, its earliest shelter, begins to hypertrophy: the rapid development which now takes place is owing to the proliferation of the cells of the stroma and the enlargement of the individual cells of all kinds, including those of the glands themselves, as well as the increase of the succulent homogeneous and cellular substance. The glands throughout their greatest extent are enlarged: the increase in thickness is more especially due to the hypertrophy of the superficial layer, the upper half, in which the stroma appears less compact, growing far above the original gland-openings, circumvallating the enlarged ostea, and thus causing those funnel-shaped depressions which give the membrane its sieve-like, cribriform appearance when seen from above. In the third month of pregnancy the mucous membrane attains its greatest thickness, forming a soft succulent lining to the uterine cavity, by its distension closing the various ostea. It is then as much as 0.236 inch in thickness in the anterior and posterior walls, lessening toward the ostea, and begins to present the characteristic layers which become so distinct in the later months—a dense upper and a very loose lower one, comparable to a lax meshwork. Its growth now ceases, and as the uterine cavity increases in size and the ovum in growth, it is distended to cover the rapidly-expanding surface, and becomes thinner and thinner, the upper dense layer remaining as such, whilst the glandular sinuses of the lower layer of the membrane are stretched transversely until they become mere flat meshes like a network stretched along the surface of the womb.
2 Engelmann Mucous Membranes of the Uterus.
The impregnated ovum, as it rapidly enlarges during the first two or three weeks, becomes imbedded in the thickened succulent decidua; and we may compare this to the sinking of a bullet into soft dough: the soft mass of the dough yields to the weight of the superimposed body, and gradually closes over it, so the tissue of these overlapping folds soon unites, completely surrounding the ovum, the nidus thus formed, in which the ovum settles, being usually in the upper portion of the fundus upon the posterior wall of the right side. We now distinguish in the mucous membrane of the uterus three parts: the decidua vera, the greater part of the membrane lining the cavity of the womb where it is not in contact with the ovum; the decidua serotina, which is that part directly beneath the ovum, between it and the uterine wall, which is in connection with the tufts of the chorion, later in part develops to form the placenta; and the decidua reflexa, that part of the mucosa which overlaps and has overgrown the ovum. This membrane is little known and rarely recognized, though always present. It is of no practical importance; a delicate membrane even at the time when it is the great safeguard of the tender ovum, serving to protect it and hold it within the soft bed formed by the decidua serotina; this function of the reflexa continues until the third month, when the ovum has developed sufficiently to occupy the entire uterine cavity and is everywhere in contact with its walls. The thin tissues of the reflexa become more transparent and delicate as they are distended and compressed between ovum and decidua vera, which now with the muscular wall of the uterus surround the ovum and continue the previous function of the reflexa.
The Development of the Ovum.—Practically, we may distinguish two periods in the development of the ovum: the first, that in which we are here interested, before the development of the placenta, where it is a cyst-like body surrounded by the shaggy chorion, the chorion velosum; and after the development of the placenta, after the fourth or fifth month, when the foetus is more fully developed and the ovum is covered with the smooth chorion, the chorion levæ.