Читать книгу Obstetrical Nursing - Carolyn Conant Van Blarcom - Страница 17

A general understanding of the physiology of pregnancy is indispensable to an appreciation of the importance of observing the present-day teachings about the hygiene of pregnancy. Upon this, in turn, must rest intelligently administered prenatal care, one of the most important branches of obstetrics.

The physiology of pregnancy really represents an adjustment of the various functions of the maternal organism, which are altered to meet the demands made upon the mother’s organs by the body which is developing, growing and functioning within hers. These adjustments are in the nature of an emergency service, since they come into existence and operate only while needed, which is during pregnancy, and promptly disappear when the need for them ceases with the birth of the child. The mother’s body then begins to return to its normal, non-pregnant state, which, with the exception of the breasts, which function for nine or ten months, is accomplished in a few weeks.

But in addition to the normal changes in physiology in the course of pregnancy, there are frequently abnormal changes, too, which may be symptoms of grave complications. The detection of these symptoms, and the employment of treatment which they indicate, constitute one of the most valuable aspects of prenatal care.

Although, as might be expected, the alterations in the structure and functions of the maternal organism are most marked in the generative organs, there are definite changes in other and remote parts of the body as well. And there are adjustments in metabolism, which, though not wholly understood, are now widely recognized as important. It is pretty generally believed that as a direct, result of pregnancy, certain substances are created, possibly by the corpus luteum, which circulate in the blood and definitely influence the maternal functions. It is possible that a development of the present imperfect knowledge of these substances will result ultimately in the discovery of a blood reaction which will serve to diagnose pregnancy in an early stage.

At present, we know that, in spite of the creation of an infant body weighing upwards of seven pounds, a placenta weighing more than a pound, together with an increase of about two pounds in the weight of the uterine muscle, all in the short span of nine months, the expectant mother has to eat very little more during this period than she ordinarily does to maintain her own bodily functions. This suggests a highly developed economy in the use of nutritive material by maternal cells.

We also know that the mother excretes waste materials for the fetus and must assume that this requires an increased, or adjusted, functional activity of her excretory organs, the skin, lungs and kidneys. Moreover, the secretory activity of the previously inactive mammary glands, in spite of their remoteness from the pelvis, suggests a nervous or chemical stimulation, or both, which occurs only during pregnancy.

The changes in the uterus itself, however, are unquestionably the most marked that take place during the period of gestation. Those that relate to the lining have been described in a previous chapter. The change and growth in the muscle wall are amazing. New muscle fibres come into existence; those already there increase greatly in size and there is a marked development of connective tissue.

The actual substance of the uterus is so increased that it is converted from an organ weighing two ounces into one weighing two pounds. From a firm, hard, thick walled, somewhat flattened body in its non-pregnant state, the gravid uterus assumes a globular outline and grows so soft that the fetus may be felt through the walls.

During the first few months the uterine walls increase in thickness, but later they grow progressively thinner, until by the end of pregnancy they are only about 5 millimetres thick.

This early growth of the uterus is doubtless brought about by general systemic changes rather than by the presence of the contained embryo. Evidence of this is found in the case of tubal pregnancies when there is a definite enlargement of the uterus during the early weeks. After the third month, however, the growth of the uterus is apparently due to pressure which the growing fetus makes on the uterine walls.

The cervix does not enlarge as a result of pregnancy, but it loses its hard cartilaginous consistency, becoming quite soft, and the secretion of the cervical glands is much more profuse.

The changes in the vagina are chiefly due to increased vascularity. The blood vessels are actually larger, the products of the glands are greatly increased and the normal pinkish tint of the mucous lining deepens to red or even purple.

The most important changes in the tubes and ovaries is in their position because of their being carried up from the pelvis by the enlarging uterus into the abdominal cavity. Although they increase in vascularity, ovulation is ordinarily suspended during pregnancy.

The abdomen as a whole changes in contour as it steadily enlarges, and the skin and underlying muscles are somewhat affected as a result. The tension upon the skin is so great that it may rupture the underlying elastic layers which later atrophy and thus produce the familiar striæ of pregnancy, known variously as the striæ gravidarium and the linea albicantes. Fresh striæ are pale pink or bluish in color, but after delivery they take on the silvery, glistening appearance of scar tissue, which they really are.

In a woman who has borne children, therefore, we find both new and old striæ; those resulting from former pregnancies being silvery and shining, while the fresh tears are pink or blue. Striæ may be found also on the breasts, hips and upper part of the thighs, and as they are of purely mechanical origin, are not necessarily associated with pregnancy alone. They may result from a stretching of the skin by ascites, a marked increase in fat or an abdominal tumor.

The same distension that causes striæ sometimes causes a separation of the recti muscles. This separation, known as diastasis, is sometimes slight but frequently very marked, the space between the muscles being easily felt through the thinned abdominal wall.

The umbilicus is deeply indented during about the first three months of pregnancy. But during the fourth, fifth and sixth months the pit grows steadily shallower, and by the seventh month it is level with the surface. After this it may protrude, in which state it is described as a “pouting umbilicus.”

The increased pigmentation at the umbilicus and in the median line is scarcely to be classified among the abdominal changes, as the skin elsewhere presents the same discolored appearance. The degree of pigmentation varies with the complexion of the individual, as blondes may be but slightly tinted while the discolored areas on a brunette may be dark brown, sometimes almost black.

The changes in the breasts during pregnancy were practically all included in the enumerated signs and symptoms of pregnancy. They increase in size and firmness and become nodular; the nipple is more prominent and together with the surrounding areolæ, grows much darker; the glands of Montgomery are enlarged; the superficial veins grow more prominent, and after the third month a thin, yellowish fluid can be expressed from the nipples. This fluid, called colostrum, consists largely of fat, epithelial cells and colostrum corpuscles and differs from milk, in its yellowish color, and in the fact that it coagulates like the white of an egg when boiled. The previously quiescent mammary glands develop very early in pregnancy an ability to select from the blood stream the necessary materials to produce a secretion. Colostrum is the product of their activity until about the third day after delivery, when milk appears.

Changes in the cardio-vascular system are among those which are not altogether understood, and it is still a moot question as to whether or not there is an actual increase in the amount of maternal blood during pregnancy. But results of the most recent investigations suggest that there is a definite increase in both the cells and the plasma. This increased amount circulating through the heart subjects it to a certain amount of strain, with the result that the organ is slightly hypertrophied and the pulse pressure is higher.

The respiratory organs do not show any marked alterations. The upward pressure of the enlarging uterus gradually shortens the height of the thoracic cavity, but if it grows sufficiently wide in compensation, there is no decrease in the capacity of the lungs. If this does not occur, the patient may suffer from shortness of breath. The larynx is sometimes reddened and edematous, a fact which explains the damaging effects which child-bearing may have upon the voice of singers.

Changes in the digestive tract during pregnancy are the morning sickness already described, and constipation. The latter is suffered by at least one half of all pregnant women, and is due chiefly to pressure of the uterus on the intestines, though impaired tone of the stretched abdominal muscles may be a factor. This condition is most troublesome during the latter part of pregnancy. There also may be gastric indigestion causing acidity, flatulence and heartburn, and intestinal indigestion giving rise to diarrhea and cramp-like pains. The appetite may be very capricious during the early weeks, and become almost ravenous later on.

Changes in the urinary apparatus include frequency of micturition mentioned among the symptoms of pregnancy.

The changes in the bony structures of the pregnant woman are characterized by partial decalcification. This is accounted for by the fact that the developing fetus requires a definite amount of calcium in the formation of its osseous structures, and unless the expectant mother absorbs an adequate quantity from her food, it must be extracted from the bones and similar structures, such as the teeth. Her bones and teeth accordingly grow softer, and we have the well-known adage, “for every child a tooth,” as well as the fact that fractures during pregnancy unite very slowly. There are also the softened cartilages which were referred to in connection with the anatomy of the pelvis. A part of the softening of the pelvic cartilages, however, is due to a temporarily increased blood supply. As will be explained in the chapter on nutrition, this partial decalcification of the mother is entirely unnecessary, and the newer knowledge of nutrition points the way to its prevention.

The skin changes consist chiefly in the appearance of striæ and the increased pigmentation to which reference has already been made. There is also an increased activity of the sebaceous and sweat glands and the hair follicles, the latter sometimes resulting in the hair becoming much more abundant during the period of gestation. Although the pigmented areas on the breasts and abdomen never quite return to their original hue, the chloasmata, sometimes called the “masque des femmes enceintes,” practically always disappear and leave no trace, a fact that is frequently a comfort to an expectant mother.

The carriage is somewhat affected during pregnancy because the increased size and weight of the abdominal tumor shifts the centre of gravity. In an effort to preserve an upright position the woman throws back her head and shoulders and finally assumes a gait that may be described as a waddle, particularly noticeable in short women.

Temperature changes are probably not caused by pregnancy per se, though some authorities believe that there is normally a slight elevation during the latter part of the day.

Mental and emotional changes are usually included among the alterations which occur during pregnancy, but the present status of psychiatry suggests that this may not be altogether true. It is a fact that many pregnant women show marked mental and emotional unbalance, but as yet there seems to be no evidence that these states are inherently due to pregnancy, though the same condition may recur in the same woman each time that she is pregnant.

We shall consider this important subject more at length in the chapter on mental hygiene, so it may be enough simply to say at this juncture that, in a sensitively strung or uncertainly poised woman, the state of being pregnant may be merely the last straw, so to speak, that upsets her equilibrium; and that some other experience, which would be an equal strain upon her slender ability to make adjustments, would result in exactly the same mental or emotional distortion, just as certain physical signs in pregnancy may be produced also in the non-pregnant state, and are not, therefore, necessarily inherent to the gravid state.

Changes in the ductless glands are in much the same category. Functional disturbances of these glands occurring at any time may give rise to great irritability, excitability or to other mental symptoms. A non-pregnant woman with even a very slight degree of hyperthyroidism, for example, may be noticeably unstable mentally or emotionally. Since there is evidently an inter-relation and inter-dependence of the functions of the ductless glands, and since ovulation, the function of one of these glands, is suspended during pregnancy, we can readily believe that other glands would undergo changes as a result. Alterations in the thyroid are particularly apparent as it becomes enlarged and more active in the majority of pregnant women, as does also the anterior lobe of the pituitary body. This increased activity may tend to compensate for the suspended function of the ovaries. But the alterations in the functions of the other glands, compensatory though they be in part, apparently produce much the same sort of nervous symptoms that they are capable of producing in a non-pregnant woman.

Taking the condition as a whole, pregnancy is usually characterized by an improved state of health. During the first few months there may be lassitude and loss of weight, but the latter part of the period is notable for an unusual degree of general well being and for an increase in flesh over the entire body, which may amount to as much as twenty-five or thirty pounds.

About fifteen pounds of the increased weight is lost at the time of labor and a still further reduction occurs during the succeeding weeks when the mother’s body returns approximately to its original condition. But it sometimes happens that the improved state of nutrition acquired during pregnancy becomes permanent.