CHAPTER II THE COURSE OF PREGNANCY
As gestation advances, the development taking place in the uterus impresses itself upon the general system. The first effect of this is manifested by certain changes in the nervous system; as for instance, emotional disturbances, perverted desire for food, and nausea and vom- iting. These manifestations are due to nerve irritability, and are spoken of as reflex.
Again, pregnancy affects the organs of excretion, the kid- neys especially, and influences the output of substances which, when retained within the sys- tem, produce poisonous or toxic effects. This is spoken of as the toxic manifestation of preg- nancy.
Later, the mere presence of the weighty uterus influences the gait of the woman and alters her carriage and figure
Fic. 3—Showing the (Fig. 3). This change consti- carriage of the pregnant tutes the physical manifestation woman ae Hise of pregnancy.
While these general changes are taking place the uterus rises toward the abdom- inal cavity and displaces the intestines.
This gives rise to the early abdominal enlarge- ment, scarcely noticeable to the woman herself, except in the feeling of slight distention it produces,
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THE COURSE OF PREGNANCY 15
There follows also an engorgement or fulness of the blood-vessels of the lower portion of the birth canal, which causes a purplish discoloration of the mucous membrane lining the vagina.
The center of active change, however, is in the uterus itself. Here the lining membrane, which is spoken of as the decidua, becomes thickened and forms a wall about the ovum, spreading not only around the latter, but completely covering it later on. That portion of the decidua lying between the ovum and the wall of the uterus, and serving as the point of attachment for the ovum, is called the decidua serotina; that surrounding the ovum, the decidua reflexa; and that lining the remainder of the uterine cavity, the decidua vera.
Changes in the Ovum.—Within the wall of the ovum itself, which appears as a minute spheric mass, the so-called embryonic portion makes its appearance. This is at first a mere swelling. It soon begins, however, to undergo changes which result in the grouping of the cells of which it is composed into different layers. From these, as development proceeds, the different structures of the body are formed: namely, the muscles, bones, brain, nerves, blood-vessels, and internal organs.
While this arrangement of cells is taking place a small double sac called the amnion arches over the back of the embryo and spreads out until it completely envelops it. The growing embryo by this time has pushed into the center of the original ovum and has severed its connection with the wall of the latter, except where it remains attached by what is later to become the umbilical cord or navel-string. Finally, the amnionic sac enfolds the cord also. It is as if the fetus—which is the proper term, instead of embryo, as soon as the umbilical cord has made its appearance— had been held by its cord and dropped into a double sac, pressing in one layer against the other
16 OBSTETRIC NURSING
until the edges of the cup-like depression which it makes are closed together about it (Fig. 4). The interior of this sac becomes filled with fluid. The sac, as mentioned above, is called the amnion, the fluid within it, the amniotic fluid.
The fetus is now attached by the umbilical cord to the placenta or after-birth, which has become developed from a layer of cells of the ovum, called the chorion. At the point of attachment between the ovum and uterus, in the early stage of the for- mation of the placenta, the chorion throws out
Fic. 4—Developing embryo suspended within the amniotic sac.
minute finger-like projections, which penetrate into the decidua. These projections grow and become united in a disk-like mass, which is the placenta.
By the time the placenta is formed pregnancy has advanced to the end of the third month or twelfth week. Before this, if the ovum should be expelled it would look like a small sac containing fluid, and surrounded by the delicate projections of the chorion. The latter give to it a shaggy appearance. The embryo is to be found within the sac, attached to the wall of the latter. At this
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THE COURSE OF PREGNANCY 7
early period its form would be scarcely perceptible. At the end of the second month it would appear as a gelatinous oblong mass, bent upon itself, with an enlargement at the head end marked by trans- verse grooves and furnished with the eyes. Development of the Fetus.—Should the fetus be expelled after the placenta has been formed, it would be seen suspended by the umbilical cord within the amniotic sac. At one point in the sac wall the placenta would be seen with the umbilical cord attached to its central portion. The shaggy chorion will have disappeared by this time.
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Fro. 5.—Fetal surface of placenta, showing the convergence of the 5" acental blood-vessels info the umbilical cord.
After the third month the sex may be made out and the fingers and toes are formed. The growth of the bones gives the fetus shape and distin- guishes it from the gelatinous form of the early embryo. It is now from 3 to 4 inches in length.
From this time on the fetus grows to resemble the full-term infant, passing through, first, a stage in which a downy covering called lanugo envelops its body, and then a stage in which it takes on the enveloping layer of fat which characterizes a healthy newborn infant.
Up until the fifth month the head is developed at the expense of the rest of the body, but in the latter weeks of pregnancy the development of the
a
18 OBSTETRIC NURSING
head and body progresses more evenly, so that the head no longer overbalances the rest of the body in size.
We must bear in mind that the most important demand of the fetus is nutrition. The only source of nutrition is from the mother’s blood. The placenta is the means by which this nutrition is supplied. The circulation of the fetus and that of the mother come in contact with each other in the placenta, not by commingling of the blood, but by the fetal blood being conveyed to the delicate branched processes in the uterine or maternal surface of the placenta. These are called villi.
Fro. 6 Diagrammatic sketch of cross-section of placenta, showing the i fioating in the blood of the placental sinuses
They float in the maternal blood current, which permeates the spaces or sinuses of the placenta. They extract from the blood the nourishment for the fetus. The umbilical cord conveys the fresh- ened blood from the placenta to the fetus and returns the venous blood. Thus a chemic inter- change between the blood of the fetus and that of the mother is constantly going on in the placenta.
It is, therefore, to be understood that the fresh- ened blood enters the fetus’s circulation through the umbilical vein instead of from the lungs, as is the case after the child begins to breathe at birth. This means a decided difference in the course of the circulation. Instead of the blood which enters
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THE COURSE OF PREGNANCY 19
the right side of the heart being conveyed to the lungs, it goes directly from the right to the left side through an opening called the foramen ovale, be- tween the auricles or fore-chambers of the heart. After supplying the various parts of the body it is directed to the artery that enters the umbilical cord and is conveyed back to the placenta. The current of blood thus ‘passes by the lungs, but takes in the placenta instead.
Enlargement of the Uterus.—This process of
Fro. 7-—Enlarged uterus containing fetus occupying the abdominal cavity.
nutrition adds to the growth of the fetus. The uterus, therefore, enlarges to accommodate the latter. The enlarging uterus may be felt at the end of the third month as a rounded mass in the lower region of the abdomen, behind the bladder. By the end of the fourth month the swelling is large enough to be seen, and at the end of the sixth month the upper portion or fundus of the uterus is more than a hand’s-breadth above the umbilicus or navel. By the beginning of the ninth month the fundus presses against the ribs, the enlargement having reached its greatest height.
After this there is a subsidence and the abdomi-
OBSTETRIC }
RSING
f nal wall seems to protrude. There is considera greater protrusion in a woman carrying her secc of third child than in a primigravida (a wom who is carrying her first child). This is due relaxation of the abdominal wall. The presel of the gravid uterus during an earlier pregnat has stretched the structures of the abdominal w and separated, to a certain degree, its muscl
} that is, more properly speaking, the recti muscl Thus, women in their later pregnancies (mult arous women) present a lax or pendulous abi men. Thus, also, the subsidence of the fund which is spoken of as lightening, is not so lik ‘o occur in multiparous women, as not only is { tate a Patt of the fetus more readily accomm sively om pelvis: but the fundus sinks prog therefore, is he seventh month on ; Lightenit estimating she’s 2 absolutely reliable’ sign advanced: ‘© period to which pregnancy