THE PROSPECTIVE MOTHER
A Handbook for Women During Pregnancy
J. MORRIS SLEMONS
Associate Professor of Obstetrics, The Johns Hopkins University.
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This book, written for women who have no special knowledge of medicine, aims to answer the questions which occur to them in the course of pregnancy. Directions for safeguarding their health have been given in detail, and emphasis has been placed upon such measures as may serve to prevent serious complications. Treatment of such conditions has not been discussed, as it can be judiciously carried out only by a physician who has the opportunity to observe and study the individual patient. Furthermore, if there is to be notable improvement in the management of cases of childbirth, the appearance of untoward symptoms should not be awaited before consulting a physician; on the contrary, prospective mothers must be taught that they should be under competent medical supervision throughout pregnancy.
At present intelligent women demand some knowledge of the anatomical and physiological changes incident to the development of the embryo and the birth of the child. These subjects do not readily lend themselves to popular description, but I have told the story as simply as possible, following in a general way the text-book of my teacher and friend, Professor J. Whitridge Williams; indeed, my main purpose has been to reproduce his book "in words of one syllable." The use of a number of technical words has been unavoidable, and, though their meaning has been given in the context, it has not been feasible to repeat the definition every time an unfamiliar term was used. On that account a glossary has been provided.
It is with pleasure that I avail myself of this opportunity to acknowledge the cheerfully given assistance of many friends. In particular I wish to thank Doctor Henry M. Hurd, until recently Superintendent of the Johns Hopkins Hospital, for his interest and advice. I am also under deep obligation to my friend John C. French, of the English Department of the Johns Hopkins University, for helpful criticism of the manuscript, and to my colleagues, Doctors Rupert Norton and Thomas R. Boggs, for valuable assistance. To many others—doctors, nurses, and patients—I am indebted for numerous suggestions which have been made either consciously or unconsciously.
J. MORRIS SLEMONS.
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In all branches of medicine the master word is prophylaxis, or prevention, and its benefits are nowhere more strikingly illustrated than in the practice of obstetrics. In former times every woman who gave birth to a child or passed through a miscarriage was exposed to grave danger of infection or child-bed fever; but at present—thanks to the recognition of the bacterial origin of the disease and of its identity with wound infection—this danger can be practically eliminated by the rigid observance of surgical cleanliness and aseptic technique. Physicians have also learned that the most effective method of coping with other serious complications of pregnancy and labor is by preventing their occurrence, or at least by subjecting them to treatment in their earliest stages; for, if they be allowed to go on to full development, the results are little better than in times past. Furthermore, a careful examination some weeks before the expected date of confinement enables us to recognize the existence of abnormal presentations and of disproportion between the size of the mother's pelvis and that of the child's head. Timely recognition of such conditions makes appropriate treatment possible and practically insures a successful outcome; while tardy recognition is frequently followed by disastrous results.
These few examples give some idea of the benefits of prophylaxis in the practice of obstetrics. Prospective mothers should understand not only that there is an advantage in taking such precautions, but that they may be risking their lives, or at least their future well-being, unless they insist upon competent medical attention. It is true, of course, that pregnancy and childbirth are generally normal processes, but they are not always so. Fortunately, most of the abnormalities give timely warning of their occurrence, and in most instances may be relieved by comparatively simple measures; or, if not, they afford indications for treatment which should lead to a happy termination. The recognition of the existence of such conditions, however, is not always easy, and their ideal treatment requires careful training and sometimes the utmost nicety of judgment. Consequently, if prospective mothers wish to be assured of the best care, they should be cautious in the choice of their medical attendant. As the ordinary layman has no means of determining the real qualifications of a physician, the choice should not be made upon the advice of casual acquaintances; but, instead, the family physician should be consulted, who, should he feel unwilling to assume the responsibility of the case, will be able to recommend a thoroughly competent substitute.
From my own experience as a teacher and consultant, I state without hesitation that in no other branch of medicine or surgery are graver emergencies encountered than in certain obstetrical complications whose treatment involves the greatest responsibility and requires the highest order of ability to insure a successful outcome for the mother and her child. For these reasons a physician should be chosen only after mature deliberation, and his services should be esteemed much more highly than is usually the case.
In order that the principles of prevention may receive their fullest application during pregnancy, labor, and the lying-in period, it is also advisable that intelligent women should possess some knowledge of the Reproductive Process in human beings. This information is imparted by Doctor Slemons' book, which I can thoroughly recommend to prospective mothers. The subject matter has been carefully chosen, and the author has wisely refrained from giving advice with regard to treatment which can be satisfactorily directed only after careful study by a physician. At the same time he has given a clear account of the physiology of pregnancy and labor, and has laid down sound rules for the guidance of the patient.
One of the most important facts emphasized by Doctor Slemons is the value of medical supervision for several weeks after the child is born; this precaution contributes greatly toward a rapid and complete convalescence. During the lying-in period the physician should supervise the care of the mother and the child, should insist upon the necessity for maternal nursing, and should keep the mother under observation until perfectly normal conditions are regained. If the latter duty is conscientiously fulfilled many years of invalidism may be saved and thousands of operations rendered unnecessary.
Although there have been notable advances in the science and in the art of obstetrics since the middle of the eighteenth century, a great many fundamental facts must yet be learned. For example, we are almost totally ignorant of the stimulus which causes the mother to fall into labor approximately 280 days after the last normal menstruation.
There are two points which I desire to impress especially upon the readers of this book. Firstly, that the advance of the science of obstetrics, and consequently improvements in its practice, must depend greatly upon the cooperation of intelligent women. They must come to realize that they will secure the best treatment only as they demand the highest standard of excellence from their attendants; and they can aid in securing this for their poorer sisters and their children by interesting themselves in obstetrical charities.
Secondly, they must realize that real progress in the science of obstetrics can be expected to proceed only from well equipped clinics connected with strong universities, and in charge of thoroughly trained and broad-minded men. As yet such institutions scarcely exist in this country. Women who are anxious to promote the welfare of their sex can find no better way of doing so than by bringing this need to the attention of wealthy men interested in philanthropy and education. Furthermore, they should bear in mind that most of our important discoveries would not have been made had animal experimentation not been available, as it is solely by this means that modern surgical and obstetrical technique has been brought to its present degree of perfection; and further progress can scarcely be expected without its aid. They should remember also that whenever they take such a well-known drug as ergot for the control of bleeding, or make use of many other apparently simple measures, they are unconsciously rendering tribute to this type of investigation.
J. WHITRIDGE WILLIAMS.
Johns Hopkins University, September, 1912.
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I. THE SIGNS OF PREGNANCY AND THE DATE OF CONFINEMENT II. THE DEVELOPMENT OF THE OVUM III. THE EMBRYO IV. THE FOOD REQUIREMENTS DURING PREGNANCY V. THE CARE OF THE BODY VI. GENERAL HYGIENIC MEASURES VII. THE AILMENTS OF PREGNANCY VIII. MISCARRIAGE IX. THE PREPARATIONS FOR CONFINEMENT X. THE BIRTH OF THE CHILD XI. THE LYING-IN PERIOD XII. THE NURSING MOTHER GLOSSARY
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The Prospective Mother
THE SIGNS OF PREGNANCY AND THE DATE OF CONFINEMENT
The Positive Signs—The Probable Signs—The Presumptive Signs: The Cessation of Menstruation; Changes in the Breasts; Morning Sickness; Disturbances in Urination—The Duration of Pregnancy—The Estimation of the Date of Confinement—Prolonged Pregnancy.
Many puzzling questions occur to the woman who is about to become a mother. Most of these questions are reasonable and natural, and should be frankly answered; but a false conventionality has—until recently, at least—forbidden any open discussion of facts connected with childbirth. The inevitable result has been that, without experience of their own to guide them, prospective mothers have sought advice from older women, whose experience was at best very narrow, and whose views were often biased by tradition. Or, distrusting such sources of information, they have consulted technical medical works which they could not understand. Either of these methods is very likely to result in misinformation and to cause unnecessary anxiety. Yet no one need be alarmed by a plain, accurate account of Nature's plan to provide successive generations of human beings. Some trustworthy knowledge of a process so fundamental should be part of every person's education; it is especially helpful to women who are pregnant because it affords a rational basis for hygienic measures which they should adopt. A popular work, however, no matter how frank and helpful it may be, will not enable one to dispense with professional advice. For the prospective mother no counsel is more important than this: Put yourself at once under the care of a physician.
Insistence on the importance of medical advice should not be taken to imply that pregnancy is to be regarded as other than a normal process. Its dangers are comparatively slight, as we should expect, since the property of all living matter to reproduce its kind is both fundamental and essential; the continuance of living creatures in this world, plants as well as animals, depends upon the Reproductive Process. And yet, natural as it is, pregnancy may be attended by complications. Such complications, though happily rare, are to be guarded against in every case, and that may be most effectually done if patients are taught to remain under competent medical supervision from the time of conception until several weeks after the child is born. This precaution greatly reduces the frequency of annoyances during pregnancy and also assists materially toward conducting a birth to a safe conclusion. Moreover, if this advice is followed, when complications do arise they will be recognized and dealt with promptly; they will not be permitted to grow more serious until, perhaps, they may jeopardize the life of the mother or the child or both.
The initial symptoms of pregnancy are so widely known that in most instances the prospective mother herself makes the diagnosis shortly after conception has taken place; but now and then pregnancy advances for several months unrecognized and is then detected by a physician who has been consulted on account of symptoms which the patient has incorrectly attributed to some other condition. On the other hand, women sometimes suspect that they are pregnant when they are not; and such mistakes occur because certain symptoms which are implicitly trusted by the laity as manifestations of pregnancy are occasionally associated with conditions quite foreign to it. It is clear that one interested in the matter must know not only what the manifestations of pregnancy are and when they appear, but also how far the evidence that they give is reliable.
The signs of pregnancy may be classified, according to their reliability, as presumptive, probable, and positive. The doubtful evidence appears first and the infallible proof last. No one need be surprised, therefore, if, when her suspicion is first aroused, she is unable to decide positively whether she is pregnant. Physicians of broad experience, possessed of facilities for observation which their patients cannot employ, may find it necessary to make more than one examination before they commit themselves to a definite opinion; in some cases, though very rarely, they must wait for two or three months to be able to do this.
THE POSITIVE SIGNS.—The earliest absolutely trustworthy manifestation of pregnancy is the motion of the fetus. The perception by the mother of these movements, which is spoken of as "quickening," generally occurs toward the eighteenth week, if she has been told to watch for them; otherwise they may pass unnoticed until the twentieth week or later. At first the motion, felt in the lower part of the abdomen, is very gentle; it has been variously likened to tapping, or to quivering, or to the fluttering of a bird's wings. As time goes on the movements grow stronger and occur more frequently; they are, however, perceived but rarely throughout the day and seldom interfere with sleep. Occasionally women are annoyed by the sensation and complain that the child is hardly ever quiet. Even these troublesome movements are never a cause for anxiety; but prolonged failure to feel motion after it is once well established should be reported to the doctor.
In the first pregnancy the passage of gas through the intestines may be mistaken for quickening long before the movements of the child are really perceptible; but those who have once experienced quickening will not be deceived. Whenever women who have borne children are in doubt the sensation is almost surely not quickening. Furthermore, in any doubtful case, the motion should be observed by a physician before being accounted a positive sign of pregnancy. This precaution will scarcely delay an absolutely positive diagnosis, since the proper method of examination reveals these movements to the physician almost as early as the patient feels them.
About the time these movements become perceptible another positive sign is available. The physician whose ear has been trained to catch such sounds when he listens over the lower part of the mother's abdomen will hear the fetal heart-beat. Other sounds may be audible there, but the character and the rate of the heart-sounds are distinctive. Since the child's heart beats almost twice as fast as the mother's, under ordinary conditions it is impossible to confuse one with the other. The mother never feels the beating of the child's heart, but occasionally she will mistake for it the throbbing of her own blood vessels.
Ability to hear the fetal heart not only provides a means of confirming the existence of pregnancy in doubtful cases, but also enables the physician to reassure his patient if she fails temporarily to feel the child move. Sometimes the presence of twins is recognized in this way. Toward the end of pregnancy the heart sounds are also of material assistance in determining what position the child has permanently assumed.
There is a third positive sign of pregnancy to which the physician has recourse, but generally it is inapplicable as early as those already mentioned. In the latter months of pregnancy it is possible to outline the child through the mother's abdominal wall. Although this procedure adds little or nothing to our resources for making an early diagnosis, the information it ultimately affords proves one of the greatest aids in the practice of obstetrics.
THE PROBABLE SIGNS.—Obviously, phenomena for which the child is responsible—such as have just been described—supply the most trustworthy evidence of pregnancy; and these phenomena alone are accepted as positive signs. But there are earlier manifestations which intimate very strongly that conception has taken place. Shortly after pregnancy has become established changes begin in the uterus, as physicians call the womb, and soon reach the point where they may be recognized by a simple examination which enables the physician to express an opinion little less than positive. As one result of pregnancy, for example, the supply of blood is increased to all the organs concerned with the reproductive process. Partly on account of this congestion and partly on account of embryonic development, the uterus becomes altered in a number of ways. Although these changes occur regularly in pregnancy, they may also occur when the womb is enlarged from other causes; therefore, if a physician should make the diagnosis of pregnancy whenever they were found, he would make it somewhat too frequently. With a little patience, however, he excludes the chance of being misled; a second examination, approximately four weeks after the first, will generally place the existence of pregnancy beyond question, for under normal conditions the degree of enlargement which takes place in a pregnant womb during a given interval is absolutely characteristic.
THE PRESUMPTIVE SIGNS.—Although women are most often led to suspect that they are pregnant by symptoms which are of such doubtful significance that they must be regarded as merely presumptive evidence, the practical value of these symptoms is attested by the fact that subsequent developments rarely fail to confirm the suspicion. Perhaps they prove misleading once or twice in a hundred cases; the number of mistakes is small, because the diagnosis is commonly made not from only one of these doubtful signs but from a group of them. In order of importance the doubtful or presumptive signs of pregnancy are these: (1) cessation of menstruation, (2) changes in the breasts, (3) morning sickness, (4) disturbances in urination.
The Cessation of Menstruation.—The failure of menstruation to appear when it is expected is nearly always the first symptom of pregnancy to attract attention, and, as a rule, when this happens to healthy women during the child-bearing period—which usually extends from the fifteenth to the forty-fifth year—it may be taken to indicate that conception has occurred. But there are exceptions to this very good rule. Besides pregnancy we are acquainted with several conditions that cause temporary suppression of menstruation; and to understand its significance we must learn something of the menstrual process itself.
Menstruation is a function of the womb and in all probability is brought about through the influence of the ovaries. The bleeding, popularly regarded as the entire menstrual process, is, in fact, indicative of only one of its stages; the others give rise to no symptoms whatever. What the stages in the menstrual process are, what relation they bear to each other, and what the significance of the whole process is, are problems that have been solved with the aid of the microscope. In this way the mucous membrane lining the womb has been studied both at the time of the periods and in the interval between them, and we have learned that it is constantly undergoing changes intended to facilitate the reception and the maintenance of an embryo. Anticipating these duties the mucous membrane receives a more abundant supply of blood; it also increases in thickness and all the structures which enter into its composition become more active. Unless conception takes place these preparations, which represent the most important phase in the menstrual process, are without value; and therefore failure to conceive means that the mucous membrane will return to the same condition as existed before the preparations were begun. The congestion is relieved by rupture of the smallest blood vessels, and there follow other retrogressive steps which completely restore the various structures to their former state. Then there is a pause, though it is not long, until preparatory changes are again initiated, or, as we say, another Menstrual Cycle is begun. Each cycle lasts twenty-eight days, and includes four stages, namely, a stage of preparation, of bleeding, of restoration, and of rest.
Although pregnancy may become established at any time during the interval between the periods of bleeding, it is more likely to be established just before a period is expected or shortly after it has ceased. Furthermore, whenever conception does take place, the preliminary preparations for the reception of the embryo are followed by much more elaborate arrangements for its protection and nutrition. Under these circumstances the hemorrhagic discharge does not appear.
Were there no other condition to bring about the cessation of menstruation, the diagnosis of pregnancy would be greatly simplified. But any one can appreciate the fact that diseases of the womb may interfere with the menstrual process. Menstruation is influenced, also, by the ovaries. As a result of age, for example, the ovaries undergo changes which invariably bring about the permanent cessation of menstruation, called the menopause. This event occurs prematurely if both the ovaries are removed by operation. In view of these facts it is not surprising that sometimes ovarian disorders abolish menstruation. An impoverished state of the blood, or nervous shock and strain, or constitutional debility may also interrupt the regular appearance of the menstrual discharge.
The value of menstrual suppression as an evidence of pregnancy is not, however, to be discounted to the extent that we might expect. This is true because the ailments which lead to confusion are relatively infrequent, and also because they exhibit characteristic symptoms which are foreign to pregnancy. Often these symptoms are obvious to the patient herself; if not to her, they will be obvious to her physician. It is about the doubtful cases, naturally, that a professional opinion is sought, and on that account physicians are perhaps inclined to overestimate the difficulty women have in learning for themselves whether or not they are pregnant. As a matter of fact, it is unusual for a prospective mother to fail to reach a correct decision—a decision for which she relies chiefly upon the suppression of her menstrual periods.
It is doubtful whether menstruation ever continues after conception has taken place. Instances in which the menstrual function is believed to persist are not uncommon, and yet in all probability the discharge regarded as menstrual has a different origin. In most cases it should be interpreted as meaning that there is some danger of miscarriage. Since miscarriage often occurs about the time a menstrual period would ordinarily be expected, there is unusual opportunity for confusing the symptoms. At all events women err much more frequently in suspecting that they are pregnant than in overlooking the condition. Indeed, pregnancy is not likely to be overlooked unless menstruation has been irregular or suppressed for a month or more previous to conception. Thus, in the case of nursing mothers in whom menstruation is already suppressed and who are, moreover, deprived of certain evidence that the breasts give, pregnancy may sometimes advance several months before it is recognized.
The Changes in the Breasts.—Various sensations in the breasts are accepted by women as a reliable sign of pregnancy; thus throbbing, tingling, pricking, or a feeling of fullness will be mentioned by one mother or another as having given her the first intimation that she was pregnant. A few women also find their breasts become tender immediately after they have conceived; this may be so marked that they cannot bear pressure. But unless such symptoms are accompanied by definite, visible changes, they have no value as signs of pregnancy.
About the end of the second month the nipples become larger and more erectile, and deepen in color. The pigmented, circular area of skin which surrounds the nipple, called the areola, also darkens. The shade that the areola assumes will vary according to the complexion of the individual, growing darker in brunettes than in blondes. Ultimately, within this pigmented circle a number of elevated spots appear about the size of a large shot. These spots betray the presence of tiny glands always located there which, on account of the better state of nutrition during pregnancy, grow larger, and generally become visible.
Usually, after two menstrual periods have been missed the breasts increase in size and firmness, and often the veins which run just beneath the skin stand out conspicuously. Before very long it is possible to squeeze from the breasts a fluid which many persons believe to be milk, though it is really colostrum, a substance that resembles milk but very slightly. At first colostrum is a clear, white fluid, but in the later months of pregnancy it becomes yellow and cloudy.
None of the changes in the breasts are absolutely characteristic of pregnancy; even the secretion of colostrum has been noted in association with various other conditions. Furthermore, as a sign of pregnancy the presence of colostrum is totally deprived of value in the case of a woman who has recently nursed an infant, for a small quantity of milk or colostrum often remains in the breasts for months after the infant is weaned. In general, however, women who have not been pregnant before should assume that they have conceived if, after missing a menstrual period, they note the characteristic changes in the breasts.
Morning Sickness.—Soon after conception many women suffer from nausea and vomiting, especially on rising in the morning. "Morning sickness" usually passes off in a few hours, although it may be more persistent. Perhaps this manifestation occurs more frequently in the first than in subsequent pregnancies, but certainly one-half, and probably two-thirds, of all prospective mothers suffer from it. Usually the nausea begins just after a menstrual period has been missed, and ceases about the third month or a little later.
But morning sickness is never counted an indication of pregnancy unless taken in conjunction with other symptoms, for individuals who are not pregnant may also suffer from nausea in the morning. On the other hand, a number of prospective mothers escape morning sickness altogether, and a few experience nausea at other times of day.
Disturbances in Urination.—It is not an uncommon belief that some characteristic change occurs in the urine shortly after conception. But this is not true; at least no change is revealed by any method of analysis known at present. Yet there are symptoms associated with the passage of the urine which appear very promptly and prevail for several weeks. Chief among these is the desire to empty the bladder frequently; some patients also have difficulty in urination, and a few experience discomfort with it. All the bladder symptoms gradually disappear about the fourth month, but become prominent again toward the end of pregnancy.
Since the inclination to empty the bladder more often than usual may be due merely to nervousness or to many other conditions, this symptom taken alone cannot be regarded as a definite sign of pregnancy. Indeed, it is mentioned, not because of its importance, but to point out that it is in no way connected with the kidneys, as patients are sometimes led to believe. It is a direct and natural result of pregnancy. Since the womb enlarges and tilts forward at a more acute angle than formerly, it presses against the bladder, giving the same sensation as when the bladder is distended with urine.
Although the presumptive signs which we have considered by no means exhaust the list, all the others are totally untrustworthy. Each of the more reliable symptoms, as we have seen, must be accepted cautiously; but taken altogether, except in very unusual cases, they may be relied upon. If, for example, menstruation has previously been regular and then a period is missed, the patient has good reason to suspect she is pregnant; if the next period is also missed and meanwhile the breasts have enlarged, the nipples darkened, and the secretion of colostrum has begun, it is nearly certain that she is pregnant; whether morning sickness and the desire to pass the urine frequently are present is of no importance. But the most characteristic evidence, we must remember, is not available until the eighteenth or twentieth week; then the signs of pregnancy are unmistakable.
THE DURATION OF PREGNANCY.—After the existence of pregnancy has become assured, perhaps the greatest interest centers about the date upon which the birth may be expected. Even to approach accuracy in this prediction the prospective mother must be familiar with certain facts which she will always observe, but which, unless she appreciates their importance early in pregnancy, she may fail to record or to remember. In a few cases, however, such exceptional information as knowing the date of conception does not lead to an absolutely accurate prediction. But the deviation from the rule will be understood only after we understand the rule itself, which is based upon what we accept as the average duration of human pregnancy, technically called the period of gestation.
In a broad sense, the period of gestation for each variety of mammal is determined by the time required for embryonic development to reach the point where the young may live independently of the mother. This point is reached more quickly with small animals than with large. The mouse, for example, generally brings forth its young in three weeks, whereas the pregnancy of the elephant lasts two years. In human beings, counting from the time of conception to the time of delivery, pregnancy continues approximately 273 days. This number is merely an estimate calculated from hundreds of cases in which there was no question as to the underlying facts. Individual cases vary notably, and indicate that two women may become pregnant on the same day and yet not necessarily be delivered at the same date.
Irregularities in the duration of pregnancy are not limited to man. Thus, while the mean period of gestation in the rabbit is thirty-one days, it may be either shorter or longer by as many as eight days. Similar variations occur in the pregnancies of all animals, and are, moreover, notably greater among larger animals, since for such animals the period of gestation is relatively long. For instance, the accurate observations of veterinarians indicate that the mean period of pregnancy in the cow is 285 days from the time of conception. This fact notwithstanding, a competent observer found that, of 160 cows, 67 were delivered before the 280th day; 68 between the 280th and the 290th day; and 25 after the 290th day. Although nothing unnatural was observed in any instance, the first animal was delivered 67 days before the last, and in 5 instances gestation continued 308 days.
In ancient times it was believed that the duration of pregnancy was of even more uncertain length in man than in the lower animals; but since the eighteenth century thirty-nine weeks have been accepted as the average duration of the human pregnancy when reckoned from the day of conception. As this date is seldom known, it is most convenient to reckon from the first day of the last menstrual period. Estimated in this way its average duration is 280 days. As this period corresponds to ten menstrual cycles, physicians prefer to describe pregnancy as lasting 10 lunar months of four weeks each. This is equivalent to 9 calendar months, in terms of which its duration is popularly stated.
THE ESTIMATION OF THE DATE OF CONFINEMENT.—Since pregnancy is not an absolutely fixed period, we possess no reliable means of predicting the exact day when it will end. The most satisfactory method of prediction consists in counting forward 280 days from the beginning of the last menstruation or, what gives the same result, counting backward eighty-five days from this date. To make the calculation in the simplest way we count back three months and add seven days; this addition is made because seven days generally represents the difference between three months and eighty-five days. If the last menstruation, for example, began on October 30th, we count back three months to July 30th and add seven days, which gives August 6th as the probable date of confinement.
A prospective mother should remember that this prediction is no more than approximate. The calculation does not give the exact date of delivery more than four or five times in a hundred cases. It is accurate within a week in half the cases and within two weeks in four-fifths. We also know that delivery is somewhat more likely to occur after the expected date than before it. But perhaps we shall get the clearest idea of the accuracy of the rule, or better still of its inaccuracy, if we imagine twenty patients to have the same predicted date, all of them giving birth to mature infants. The chances are that only one of these patients will be confined upon the day predicted; nine will be confined before and ten after it. In all probability five of those who pass the predicted day will be delivered within a week and four others within the second week, while the twentieth patient will not be delivered until three weeks or more have elapsed.
Such results clearly indicate our inability to make accurate predictions even though pregnancy is normal in every way. Whenever patients pass their expected date uneventfully, if they will bear in mind that the fault lies with the method of prediction and not with the pregnancy, they will often be saved anxiety. Frequently such discrepancies are attributable to a false assumption, for our rule always assumes that the conception took place immediately after a menstrual period. While this is generally true, the number of cases in which it occurs just before the period to be missed is by no means inconsiderable, and in these we should not expect pregnancy to end until two or three weeks after the day predicted by the rule.
Occasionally patients know the precise day upon which conception took place, and prefer to estimate the day of confinement from that rather than from the beginning of the last menstruation. They may do so by counting back thirteen weeks from the day of conception; but this method also is subject to error for, as we have noted, the duration of pregnancy reckoned in this more exact manner is not constant. Such a calculation rarely offers any advantage over that made from the menstrual record.
Another method of estimating the date of confinement is based upon the assumption that fetal movements are first perceived by the mother toward the eighteenth week of pregnancy; and in consequence twenty- two weeks generally elapse between quickening and the day of delivery. Although such a calculation is far from certain in its prediction, there are instances in which no other calculation can be made. A nursing mother, for example, may become pregnant before menstruation has been reestablished. Under these circumstances, obviously, the date of confinement cannot be estimated in the ordinary way, and it is then especially important to know the first day on which the fetal movements were felt. Furthermore, it is helpful to note this date in every case, since it serves, if for nothing more, to confirm the prediction made from the menstrual record. Besides the two methods just described, which are alike in that they require the patient herself to make the necessary observations, there is a third method of estimating how far pregnancy has advanced, by which the physician is enabled to draw his own conclusions. This method is based upon the fact that the womb enlarges from month to month during pregnancy at a constant rate. Up to the end of the third lunar month it cannot be felt through the abdominal wall; but in the course of the fourth month, on account of its size, it must rise into the abdominal cavity. At the beginning of the sixth month the top of the womb is at the level of the navel, and at the ninth reaches the ribs. The diaphragm then prevents the womb from going higher; and two or three weeks before the end of pregnancy it drops several inches, causing a change in the figure which is noticeable to the patient, since her skirts hang somewhat lower than before. From this time on she is more comfortable, because the lungs are not crowded, and there is less interference with breathing.
These alterations in the position of the womb indicate very satisfactorily the month to which pregnancy has advanced, but not the week and much less the day. They do not afford a more accurate means of predicting the date of confinement than does quickening. The evidence gained from the position of the womb, like that afforded by the beginning of quickening, generally confirms the prediction made from the menstrual history; it serves only occasionally to correct it.
PROLONGED PREGNANCY.—Since birth does not occur in many cases until the predicted date has been passed, it will be helpful even at the cost of repetition to sum up what we know in explanation of such unfulfilled predictions. They are to be explained sometimes by uncertainty as to the beginning of pregnancy, as for example by the supposition that conception took place shortly after the last menstrual period, whereas it actually occurred two or three weeks later. In a few instances, however, errors of observation or of calculation will not account for false predictions.
It is generally admitted that second pregnancies average somewhat longer than first pregnancies; one series of statistics indicates that the duration increases slightly with each pregnancy up to the ninth and decreases after that. Pregnancy is protracted more frequently in healthy women than in those who are not, and again more frequently in those who are inactive than in those who work. With twins, contrary to the popular belief, pregnancy is apt to end before, not after, the expected date. The sex of the child, in all probability, has no influence upon the duration of pregnancy.
As we might expect, individuality is also a factor in this problem. Thus, the period of gestation with some women is regularly longer, with others habitually shorter than the accepted average. Until experience has demonstrated their existence, generally, such peculiarities are overlooked. But occasionally they may be detected from knowledge of the interval between the menstrual periods; an unusually long interval between them, for example, would lead us to anticipate a protracted pregnancy.
Any delay after the expected date of birth has arrived taxes the patience of the prospective mother. The fact, however, that more than 280 days have passed since the last menstruation, does not necessarily mean that a patient has gone "over time." Such a question can be decided solely from the weight and length of the child. Judged in this way, comprehensive statistics indicate that once in several hundred cases pregnancy may be fairly called prolonged. Even in these rare instances an examination about the time of the predicted date makes it clear whether pregnancy should be artificially ended or be allowed to proceed to its natural conclusion.
THE DEVELOPMENT OF THE OVUM
The Germinal Cells—Fertilization—The First Steps in Development— The Reaction of the Uterus—The Amniotic Fluid—The Placenta—The Umbilical Cord.
Pregnancy, besides changing the external form of the body, causes sensations—as for example those due to fetal movements—which are so distinctive that they cannot escape notice. These obvious evidences of approaching motherhood naturally lead thoughtful women to wonder about the hidden mechanism of development, a mechanism which, of itself, causes no sensation whatever. It is for this reason, perhaps, that a prospective mother's imagination is so apt to be unusually active, often picturing absurd conditions as responsible for one symptom or another. Those who give free play to the imagination in regard to the formation and progress of the embryo are pretty certain to arrive at erroneous if not grotesque conclusions; for example, they may attribute a protracted pregnancy to the child's having grown fast to the mother, a situation that cannot arise.
Of course it is not essential that a prospective mother should understand what is happening within the womb. And upon those who prefer to be ignorant of the mechanism of development I would not urge another point of view, for not ignorance but the unchallenged acceptance of "half-truths" and of totally incorrect explanations is the chief source of harm. On the other hand, my own experience has taught me that women who wish to know about development should be told the truth. In accord with this is the fact that I never have more satisfactory patients than those who have previously been trained nurses and who, in preparing for that profession, received instruction concerning the reproductive function of human beings.
A description of development, in order to be perfectly clear, must begin with a word about the fundamental structure of the adult body. Everyone knows that the various parts of the body perform different functions; but not everyone, perhaps, realizes that, in spite of their different functions, all the organs of the body are composed of similar structural units, known as cells. Of course, cells are definitely arranged according to the use for which the tissue that they chance to compose may be designed; they have, moreover, distinctive individual peculiarities which can be easily recognized under the microscope; but the essential features of the cells remain the same, wherever they may be located. That is to say, each cell is a minute portion of living matter, or protoplasm, separated from its neighbors by a partition, the cell-membrane; each has its own seat of government, the nucleus, located near its center; and each, to all intents and purposes, leads an individual existence.
THE GERMINAL CELLS.—Many of the cells in the human body are able to produce others of their kind. This they do virtually by growing and splitting in half; cell-division, as this splitting is called, really represents reproduction reduced to the simplest terms. Most cells can do no more than produce units like themselves. The bodies of women contain, however, a type of cell which possesses a far more wonderful power. Provided the requisite conditions for such development are met, these cells are capable of developing into human beings. Each of these remarkable units is called an Ovum, or egg-cell, and represents one variety of the germinal cells. But the other variety, represented by the Spermatozoon and developed only in the male sex, is also required for the production of a human being.
Every ovum originates in the ovaries. These are organs peculiar to women, having the size and shape of large almonds, and placed in the lower part of the abdominal cavity. Though the ovaries are two in number, one alone is sufficient for every requirement of health. It has been estimated that the ovaries together contain at the time of birth about 40,000 ova, distributed equally between them. Since less than 500 ova are required to insure regularity in the menstrual function, it is clear that, if the surgeon finds it necessary to remove one of the ovaries, the other will provide abundantly for menstruation and for the bearing of children. Although every ovum that will be produced as long as a woman lives has already sprung into existence by the time she is born, not a single one ripens for from twelve to fifteen years. The ripening process begins about the time of puberty, and, unless suspended through the occurrence of pregnancy, continues until the menopause. During this period, which is also characterized by the periodical appearance of menstruation, one ovum ripens each month; sometimes, though rarely, several ripen at once, and this tendency is partly responsible for twins.
The human ovum is a tiny structure, measuring about 1/125 of an inch in diameter. With the naked eye it can barely be seen; magnified by the microscope it appears as a little round bag made of a transparent membrane. Briefly described, the ovum is a single cell. That is, it belongs to the simplest class of anatomical structures, and is one of the millions upon millions of units that make up the body. It contains a nucleus surrounded by nutritive material, the yolk. Yet the quantity of yolk is exceedingly small. In this particular the human ovum differs notably from the egg of birds, as it does also in that it lacks a shell. Obviously, a shell would not only be useless to an embryo developing within the body of its parent, but would shut off the nourishment, which, since the ovum contains so little, must necessarily be provided by the mother.
When the ovum has ripened, it becomes detached from the ovary, and enters a fleshy tube about the size of a lead pencil, known as the oviduct. There are two of these tubes, one running from the neighborhood of each ovary; both enter the uterus, but on opposite sides. The ovum travels down the tube which corresponds to the ovary where it originated. The journey is fraught with momentous consequences, for it is during this passage through the oviduct that the fate of the ovum is determined. If it is to develop into a living creature, a great many conditions must sooner or later be fulfilled; but there is one which must be promptly satisfied. Shortly after leaving the ovary the ovum must receive the stimulus to live and grow; otherwise it will quickly wither and die. This vital stimulus can be imparted only by the spermatozoon.
The male germinal cell is like the female cell in the possession of a nucleus; in other respects it is very different. Longer but much narrower than the ovum, the tiny arrow-shaped spermatozoon is particularly distinguished by its active motility, for it has a tail that propels it. The human male cell must travel some distance to reach the point where it can meet a ripe and vigorous ovum; and since the journey is not without danger to its life, Nature has provided that exceedingly large numbers of the male cells shall be deposited in the vagina at the time of the marital relation. In this way, it is made sure that some of them will travel up through the uterus and oviducts, arriving in the neighborhood of the ovaries.
FERTILIZATION.—Convincing observations upon the lower forms of life, especially upon fishes, have shown that when the germinal cells come near to each other, the ovum attracts the spermatozoon. The power of attraction which the ovum exerts may be likened, most simply, to the influence of a magnet upon iron-filings. While there has been no opportunity to observe such attraction between the parent cells of human beings, its existence is not open to doubt. And it is practically certain that these cells meet in the oviduct, even in that portion of it which receives the ovum just as it leaves the ovary. Thither a number of the male cells have traveled by their own activity; several come in contact with the ovum and one, but only one, actually enters it. Almost at the moment when they touch, the two cells unite so intimately that all trace of the spermatozoon is lost. Fertilization of the ovum, as this event is scientifically termed, has as its main purpose the uniting of the nucleus of a male germinal cell with the nucleus of the female germinal cell. This detail has been carefully studied; we know that the nuclei quickly blend into one, and that the particles of living matter contributed by the male animate the female cell with a new and wonderful activity.
In our every-day way of speaking, fertilization means conception; it is the instant in which a living being begins its existence. There is no longer the slightest excuse for confusion regarding the period at which the life of the unborn child begins. Before the significance of fertilization was understood, it was perhaps not unreasonable to believe that life began with quickening or about the time the fetal heart-sounds could be heard. But now we must acknowledge that both these ideas were incorrect. The animation of the ovum at the moment of conception marks the beginning of growth and development which constitutes its right to be considered as a human being.
Individuality, hereditary traits, sex—all these, we may be sure—are unalterably determined from the moment of conception. The germinal cell forms the total contribution of the male parent to pregnancy; therefore no other opportunity for him to influence his progeny presents itself, and the substance which enters the ovum at the time of fertilization must be the basis of inheritance from the father. It is equally true, as we shall see in the next chapter, that the nucleus of the ovum and the nucleus alone transmits maternal qualities. The material which conveys inheritable characters can be seen and has been identified in both germinal cells; from each of them the fertilized ovum derives equal amounts. As the parental nuclei unite, the material which they contain intermingles and establishes a new being; to attain full development, it requires nothing further from the father, and nothing save nourishment from the mother.
THE FIRST STEPS IN DEVELOPMENT.—Although the identity of the spermatozoon is lost at the moment of fertilization, its influence just then begins to be asserted. In the fertilized ovum the dawn of development is shown at first by unusual activity within and later by alterations upon the surface. Before very long the circumference of the cell becomes indented as if a knife had been drawn around it, and shortly two cells appear in place of one. These two cells in turn divide, yielding four cells which grow and divide into eight. In this manner division follows division until a multitude of cells have sprung into existence, all of which cling together in the shape of a ball. Development always proceeds in the same orderly way; evidently it is governed by fixed laws which decree that the mass shall remain for a while in the form of a ball, though the ball, at first solid, soon becomes hollow.
While these changes are taking place the growing ovum is carried down the oviduct a distance of four to six inches and finally comes to rest in the uterus, where it is to dwell during the months necessary to its complete development. The time consumed by this journey cannot be measured accurately; it may be as short as a few hours or as long as several days, but in all probability it is never longer than a week. Although the element of time is uncertain the method of transmission is well understood. Of its own accord the ovum can move after fertilization no better than before; it is never capable of moving itself. The active agent of transportation is the oviduct, which has been fitted for this purpose with millions of short, hair- like structures that project into its interior. These are closely set upon the inner surface of the oviduct; their outer ends are free and continually sway to and fro like a wheat field on a windy day; and by their motion they create a current in the direction in which the ovum should move, namely, toward the uterus. While passing through the oviduct, the ovum has no attachment whatever to the mother, yet development is going on all the time. It is thus made perfectly clear that development is not directed by the parent. This independence of the parent, though it continues to be one of the characteristic features of the development of the ovum, shortly becomes less evident, for communication is set up between the mother and the ovum as soon as it reaches the uterus. Unless we were warned, we might easily misinterpret the significance of this attachment to the parent. It does not permit the mother, for instance, to influence the mind or character which the child will have. The purpose of the attachment is twofold, namely, to anchor the ovum, and to arrange channels by which, on the one hand, nutriment may reach the embryo, and, on the other, its waste products may return to the mother. The mother may influence the nutrition of the fetus; but she cannot determine the kind of brain or liver her child will have; neither for that matter can she alter the development of any portion of the embryo.
After its entrance into the cavity of the uterus prepared to receive and protect it, the mass of cells sinks into the soft, velvety lining of the organ. Here it is entirely surrounded by tissue which belongs to the mother. But just before implantation takes place the architecture of the ovum is modified in such a way as to indicate the trend of its subsequent development. We left it, a hollow ball passing down the oviduct; had we examined the sphere more closely we should have found its wall composed of a single layer of cells. At one spot, however, the wall soon thickens. The thickening is due to a specialized group of cells which gradually grows toward the hollow center of the ball. A little later, if we study the structure as a whole, we find it a small, distended sac, from the inner surface of which hangs a tiny clump of tissue. The clump of cells within and the inclosing sac as well are both requisite to the ultimate object of pregnancy; yet they fulfill very different purposes. The clump within will mold itself into the embryo; the inclosing sac will make possible the continued existence and growth of the embryo by securing and conveying to it nourishment according to its needs. These two structures, which from now on constitute the ovum, can best be considered separately and in the order of their development. We shall therefore first study the sac and in the next chapter the embryo.
For a time after this sac, or ball, as you may choose to think of it, becomes implanted in the uterus, every part of its wall shares in the responsibility of procuring nourishment for the embryo. On this account the wall, or capsule, is for several weeks the most conspicuous part of the ovum. Its position is naturally advantageous, for, since it forms the outermost region of the structure and comes into immediate contact with the tissues of the mother, it has the first opportunity to seize and appropriate nutriment. Consequently, while there is still relatively little development in the embryo, the capsule of the ovum gives evidence of rapid extension; the wall becomes thicker, and the circumference of the sac increases. The significant thing about this growth, however, is the fact that it does not progress evenly. At some points cell-division is more active than at others, with the result that the surface of the ovum speedily loses its smooth, regular outline. Projections from the capsule appear; they increase in number and in length; and by the end of four weeks the ovum, as yet less than an inch in diameter, resembles a miniature chestnut-burr. To make the comparison more accurate, we must imagine such a burr covered with limp threads instead of rigid spines.
These projections, the so-called Villi, push their way into the mucous membrane of the uterus and serve a two-fold purpose. One of their functions is to fix the ovum in its new abode; and, though the attachment is not at first very secure, it becomes stronger in the course of time and is capable of withstanding whatever tendency the activity of daily life may have to loosen it. The other, and equally important, task of the villi, the majority of which dip into the mother's blood, is to transmit substances to and from the embryo.
We have traced thus far the earliest steps in the development of the ovum. One portion, we observed, was promptly set apart for the construction of the future child; this favored portion became inclosed by all the rest of the ovum, which has a more or less spherical form and is technically called the fetal sac. The first duty of the sac is to take root in the womb, and the second, no less vital, is to draw nourishment from the mother. But neither of these functions can be performed without the participation of the uterine mucous membrane, the soil, as it were, in which the ovum is planted. We must now learn how the maternal tissues assume the responsibility placed upon them.
THE REACTION OF THE UTERUS.—The womb, which is small before marriage, is converted by pregnancy into the largest organ of the body. The virginal uterus, shaped somewhat like a pear, and placed with apex downward, is carefully protected within the bony basin between the hips, which is commonly called the Pelvis. The upper and larger part of the organ, known as the body, lies at the bottom of the abdominal cavity; the lower part, the neck, projects into the vagina. The cavity inside the womb communicates above with the two oviducts and terminates below in a canal which runs through the neck and opens into the vagina by an orifice known as the mouth of the womb.
Pregnancy modifies every portion of the womb in one way or another; but the most profound alterations occur in the body, in the cavity of which the ovum has come to rest. During the forty weeks of gestation the organ grows in weight from two ounces to as many pounds; from three inches in length it increases to fifteen inches; and its capacity is multiplied 500 times.
The mucous membrane which lines the cavity of the uterus responds to the stimulus of pregnancy in a characteristic manner and with a single purpose, namely, to promote the development of the ovum. In connection with menstruation we noted that this membrane periodically prepares for the reception of an ovum. And if the expected ovum has been fertilized, its arrival is followed by arrangements for its protection and nutrition which are far more elaborate than the preparations for its reception. Within a few weeks the mucous membrane becomes half an inch thick, that is, about ten times thicker than it was; and all the elements entering into its composition, become unusually active. The blood-vessels are congested; the glands pour out a more elaborate secretion; and certain cells lay up a bountiful store of material to be drawn upon in the formation of the embryo and the building up of the structures that promote its development.
The ovum is as likely to find a resting place at one spot as another upon the surface of the uterine mucous membrane. The whole of that surface has been made ready to receive it; yet the area actually required to imbed the tiny object is extremely small. As the ovum escapes from the oviduct and enters the womb, it is smaller, in all probability, than the head of a pin. For at least a week after its coming, diligent search is necessary to find the site of implantation. Insignificant as it is at first, however, the region of implantation later becomes very prominent, for it undergoes a transformation that the rest of the mucous membrane does not share. That is to say, it becomes the point of attachment of the Placenta, an organ that has the very important function of drawing upon the resources of the mother's blood. As the ovum sinks into this especially prepared bed, the villi are formed. They break open the adjacent capillaries of the mother, thus diverting her blood from its accustomed course. The blood collects in microscopic lakes in contact with the capsule of the ovum, and from them flows back into the mother's veins. Through the veins it returns to her heart, by which it is distributed through the arteries to the various regions of the body. The tiny lakes, in which the villi hang, are thus made a part of the mother's circulation and as such are regularly replenished with purified blood. By this means the ovum receives a rich supply of nutriment, and as a natural consequence its growth is rapid.
Before very long the diameter of the ovum is greater than the depth of the mucous membrane which surrounds it. Consequently that part of the membrane which covers it is pushed into the uterine cavity, as the ground is raised by a sprouting seed. Growth continues, the bulging increases, and extensive alterations are wrought both in the womb and in the capsule of the ovum. One of these alterations will be more easily understood if we still think of the ovum as a seed, for it grows away from its roots just as plants do. Most of the capsule, therefore, is removed step by step farther from its source of nourishment, for the maternal blood-vessels do not follow the expanding sac but retain their original position at its base. Partly on account of the lack of nutriment thus occasioned and partly on account of the distention caused by the contents of the sac, atrophy occurs in the distant portions of the sac's wall. As a final result of these two factors, the maternal tissue which covers the ovum becomes thinned and stretched; it is pushed entirely across the uterine cavity; and by about the twentieth week meets the opposite side of the cavity, to which it becomes adherent. Subsequently, the sac which incloses the embryo becomes everywhere fastened to the inner surface of the uterus and completely fills the uterine cavity.
THE AMNIOTIC FLUID.—The great enlargement of the uterus which is so marked a characteristic of the latter part of pregnancy is due in a measure to the luxuriant blood-supply, for better nutrition always causes growth. In a far larger measure, however, it is due to distention for which the product of conception is responsible. Beside the fetus the inclosing sac also contains a considerable quantity of fluid. This fluid, called "The Waters" by those who have no special knowledge of anatomy, is technically designated as the Amniotic Fluid.
In the earlier months of pregnancy the amniotic fluid is not abundant; later it increases rapidly, so that by the end of the period it measures about a quart, and frequently even more. The slightly yellow amniotic fluid is itself clear, but small particles of dead skin and other material cast off from the surface of the child's body are floating in it, and may cause turbidity. The absence of odor supports the view that this fluid is not the child's urine. The evidence thus far adduced, though not absolutely conclusive, gives good reason to believe that "the waters" are secreted by the inner side of the sac which incloses the fetus. Very early in pregnancy this sac becomes a double-walled structure; and, though its layers are intimately blended, and together measure not more than 1/16 of an inch in thickness, with a little care they can be separated. The outer layer, which comes in contact with the inner surface of the uterus and has to do with the matter of nutrition, is called the Chorionic Membrane; the inner, the so-called Amniotic Membrane, is much the stronger and is devoted to the protection of the embryo, which it completely surrounds with fluid, at the same time retaining the fluid within set bounds.
The amniotic fluid performs many important duties. Perhaps the first, in point of time, is to provide sufficient room for the embryo to grow in. Later, as the fluid increases, it permits the fetus to move freely, and yet renders the movements less noticeable to the mother. Again, the amniotic fluid prevents injuries that might otherwise befall the child in case the mother wears her clothing too tight. Harmful as the practice of tight-lacing during pregnancy is, it does not, thanks to the presence of the amniotic fluid, result in the disfigurement of the child. For the same reason a blow struck upon the abdomen, as in a fall forward, is not so serious as might be thought, since the fluid, not the child, receives the force of the impact. Some physicians believe that the fetus swallows the amniotic fluid and thus secures nourishment. The fluid also serves to keep the fetus warm; or, to be more exact, protects it from sudden changes in the temperature of the mother's environment. Normally the temperature of the fetus is thus kept nearly one degree higher than the temperature of the parent.
Ultimately, the amniotic fluid assists in dilating the mouth of the womb, which remains closed until the beginning of the process that terminates with birth. The uterine contractions at the onset of labor compress the fluid; in turn the fluid attempts to escape but is held in check by the amniotic membrane, which it drives into the canal leading from the uterine cavity to the vagina. Acting like a wedge, the fluid gradually pushes the mouth of the womb wider and wider open, until it is large enough for the child to pass. The sac usually ruptures when that point is reached, the fluid escapes, and in due time the child is born. This is followed within half an hour by the extrusion of a mass of tissue—in reality the collapsed fetal sac— which in every language, so far as I know, is named the After-Birth. An examination of this tissue at the time of delivery repays the physician, for it is important to ascertain that none of it has been left in the uterus. Our interest at present, however, is to learn how the after-birth has assisted toward the growth of the child.
THE PLACENTA.—The after-birth has puzzled scientists as well as the laity, and not until comparatively recent times have its origin, structure, and use been satisfactorily explained. Its meaning profoundly interested primitive men and stimulated their imagination scarcely less than the mystery of conception. Some uncivilized tribes believed that the after-birth was animated like the child; consequently they spoke of it as "the other half," and often saved it to give to the child in case of sickness. But generally the after- birth was buried with religious ceremony, and was occasionally unearthed later to discover whether the woman would have other children; the prophecy was made according to the manner of disintegration or some other equally absurd circumstance.
The after-birth consists of a round, fleshy cake, the placenta, to which two very essential structures are attached. One of these, running from one surface of the cake, is a rope-like appendage, the umbilical cord, which links the placenta with the fetus. The other, attached to the circular edge of the cake, is a thin veil of tissue, in some part of which a rent will be found. Now, if we lift the margin of the rent, we shall see that the veil and the cake together form a sac which we are holding by the opening. This aperture through which the fetus passed, and it was really made for that purpose, was formerly placed over the mouth of the womb; the sac itself, distended by the fetus and the amniotic fluid, was fastened everywhere to the inner surface of the womb.
It is plain that we have now in our hands the fetal sac, the development of which we have already traced from the beginning. The wall of the sac, it will be recalled, was originally of the same formation throughout; but when the ovum became imbedded in the womb, that part of its capsule which remained in permanent contact with the mother's blood underwent special development, whereas the rest of the capsule gradually pushed away from its primary position and, becoming stunted in its growth, even lost to some degree the development it had attained. This latter portion, the veil that passes from the edge of the placenta, is formed of the two membranes we have mentioned, namely, the chorion and the amnion.
The placenta is, for the most part, a highly developed portion of the chorionic membrane, which became specialized simply because it happened to receive the best supply of blood. At the time of birth the placenta measures nearly an inch in thickness, is as large around as a breakfast-plate, and generally weighs a pound and a quarter, that is, approximately one-sixth of the weight of the child. This relation between the weight of the placenta and of the child is regularly maintained; therefore, the larger the child the larger the placenta associated with it.
The placenta has two surfaces, easily distinguished from each other. The raw maternal surface was formerly attached to the inside of the uterus; the fetal surface, covered by the amniotic membrane, was in contact with the amniotic fluid. Across the fetal surface run a number of blood-vessels containing the child's blood, converging toward a central point at which the umbilical cord is inserted. The point at which the cord is attached affords the simplest means of distinguishing the two surfaces of the placenta.
Our knowledge as to how the exchange of food and excretory products between mother and child is carried on by the placenta has been gained chiefly through the microscope. The oldest medical writings, as we might suppose, express very fanciful ideas regarding the nature of embryonic development and the means by which it is made possible; no rational view of these matters could exist until the circulation of the blood was described by William Harvey in 1628. After this epoch-making revelation, it was accepted as true that the mother's blood entered the unborn child and returned to her own system. But that view eventually became untenable, for it was proved conclusively that there is no communicating channel between the two. For years after that, it was believed that before birth the womb manufactured milk to sustain the child, just as the breasts do afterwards; but this theory also was disproved; and, as I have said, only by the use of the microscope have we learned the truth about fetal nutrition.
When thin slices of the placenta are magnified they are found to contain countless numbers of tiny, finger-like processes; these are the villi, and they constitute the major portion of the organ. The villi seen in a mature placenta are the same as those which projected from the capsule of the young ovum, but not these alone, for many branches have sprouted from the original projections. The primary trunks with all their branches hang from the capsule of the ovum and extract nutriment from the mother's blood which surrounds them, just as the roots of a tree extract it from the soil.
The interchange of material between mother and child as carried on in the placenta can, perhaps, be made clearer if we compare one of the trunks and its branching villi to a human forearm, hand, and fingers. The hand, we will imagine, is held in a basin of water, in which, by turning on a spigot and leaving the outflow unstopped, we have arranged that the water changes constantly. In terms of this illustration, the water corresponds to the mother's blood, rich in oxygen, mineral matter, and all other kinds of essential nutriment; and the fingers are the villi. The blood-vessels in the fingers, to go a step farther, represent the blood-vessels which exist within the villi, connecting with the umbilical cord, and passing by that route to the body of the child. The blood which thus circulates through the villi, it is important to emphasize, is the child's blood; it cannot escape through the coating of the villi, just as our blood cannot escape through the skin of the fingers. Similarly, the mother's blood cannot enter the child; the two circulations are absolutely separate and distinct.
It must be noticed, moreover, that the maternal blood not only brings to the surface of the villi everything the child needs, but it also takes away the waste products of fetal life. Let us select one of the foodstuffs necessary for the unborn child, and follow its course so far as it relates to fetal nutrition. The mother's blood brings sugar, for example, from her intestinal tract to the surface of the villi; through the coating of the villi the sugar passes into the fetal blood, is carried to the fetal heart, and distributed to the various fetal organs. They burn it, deriving heat and energy, and in return give off waste products, namely, carbonic acid gas and water, which are taken up by the fetal blood, borne back to the placenta, and pass again through the coating of the villi into the mother's circulation. These waste products are then transported to the mother's lungs and to her kidneys, and are finally thrown off from her body. Before the child is born, therefore, the placenta, which is an aggregation of villi, acts as its stomach, intestines, lungs, and kidneys.
In every pregnancy the placenta serves in this way as an organ of nutrition, arranging for the passage of food from the mother's blood to the fetal circulation. Occasionally, it is interesting to observe, the placenta performs a very different function, namely, the protection of the unborn child from diseases that may attack the mother. It is able to afford such protection, because the coating of the villi is not permeable to all sorts of substances. In order to pass through their walls, material must be in solution; solid bodies, therefore, are denied admission to the fetal circulation. The most significant result of this restriction is, perhaps, that so long as the coating of the villi remains intact and healthful, bacteria cannot gain access to the unborn child. Since in health there are no bacteria in the mother's blood, this fact has no bearing upon the average pregnancy; but in those exceptional cases in which typhoid fever or some other infectious disease appears during pregnancy, it is gratifying to know that Nature has provided an unusual defense against infection of the unborn child.
That we do not know all about the interchange of substances between mother and child must be admitted; but the essential facts, and they alone are of interest here, have been established beyond contention. There is no doubt whatever that the mother's blood surrounds the placental villi but never enters the child. The fetal blood, on the other hand, is first in the child's body, then in the villi, and then returns to the child again. It never enters the blood-vessels of the mother but passes to and from the placenta as long as pregnancy lasts.
THE UMBILICAL CORD.—This rope-like structure, familiarly known as the navel-string, which connects the placenta and the fetus, is approximately twenty inches long; its length, therefore, is sufficient to permit the newly born child to lie between the mother's knees while the placenta remains attached to the womb. The cord is about the thickness of the thumb and contains three blood-vessels, all filled with fetal blood; in two of them the current is directed toward the placenta, the third carries the blood back to the fetus after it has circulated through the placental villi. In the cord the vessels lie near together and are encased in a jelly-like substance that protects them from injury.
So far as is known; the umbilical cord performs no service other than to link the blood-vessels in the placenta with those in the fetus. Simple as this may seem, it is of paramount importance in maintaining the life of the fetus, for compression of the vessels in the cord would shut off its nutriment. Against such accident, however, perfect provisions have been made; both the amniotic fluid and the jelly-like substance which surrounds the vessels are safeguards which effectually protect the circulation from pressure that might interrupt it.
Frequently, prospective mothers are told they must not "reach up" for fear the cord will become entangled. Such a precaution is quite unnecessary. No matter what the mother does, or does not, the cord will be found around the child's neck at the time of birth in one of every three cases. It is not difficult to understand how this happens. The cord is longer than the uterine cavity and must fall in coils toward the bottom of it. Now, since the fetus is free to move it enters and withdraws from these loops, many times, in the course of pregnancy. Finally, when it takes up a position head downward, as it nearly always does, the head is the part of the fetus which passes through the coil, should one happen to lie in its path. After the head is delivered the physician always feels about the neck to discover whether a loop of cord is there. If it is, he can release it easily. This condition, since it occurs so frequently and since it so rarely produces harmful consequences, should not be considered unnatural.
After the child is born, the physician cuts the cord, and in due time the after-birth is expelled through the same passage as was the child. The expulsion of the after-birth frees the mother of all the tissue derived from the growth of the ovum, for the intricate mechanism that served to nourish and protect the embryo was almost entirely developed from the ovum itself. It is a remarkable provision of Nature that very little of the mother's tissue is cast off at the end of pregnancy; and even this small portion is promptly replaced. By about the sixth week after delivery, the wound which was made by the separation of the fetal sac has completely healed. Meanwhile the mucous membrane that underwent elaborate preparations to receive the ovum, the cavity that was adjusted to its growth, and the muscle fibers that were strengthened to insure its safe entry into the world have all regained their original state. Except for the activity of the breasts, the mother is left in the same physical condition as before she became pregnant.
The Development of Form—The Determination of Sex—Twins—The Rate of Growth—The Newborn Infant—Heredity—Maternal Impressions.
The new human being begins existence, as I have shown, as soon as the ovum is fertilized, though at that moment it consists merely of a solitary cell formed by the union of the two parental cells. From a beginning relatively simple the human body develops into the most complex of living structures; and, startling as it may appear to be, it is demonstrably true that every one of the millions of cells which compose an adult has descended from the ovum. Furthermore, the individual himself is not the entire progeny of the ovum; the placenta and the membranes dealt with in the preceding chapter, we saw, were also derived from that same source. They possess only a transitory importance, to be sure, and to most persons they are less interesting than the embryo, yet we gave them consideration before discussing its growth because the manner in which the ovum becomes attached to the womb and draws nutriment from the mother primarily determines the fate of a pregnancy.
Now that we have become familiar with the arrangements for the protection of the embryo, we are prepared to learn how it develops, and may accept the phrase, embryonic development, to cover the whole period of existence within the womb. In a more technical sense, however, the use of the term embryo is limited to the first six weeks of pregnancy and designates the condition of the young creature before it has acquired the form and the organs of the infant; after that time the unborn child is called a fetus. Embryonic development, therefore, in the strictest sense of the term, chiefly involves the shifting of various groups of cells and the bestowal upon them of different kinds of activity. During this period comparatively slight growth takes place. By about the twentieth week, the house, it may be said, is set in order; and there follows a period marked by the rapid growth of the fetus.
THE DEVELOPMENT OF FORM.—A very old explanation of embryonic development was that the process consisted altogether in growth. According to that view the embryo lay curled up in the egg; at the outset it was equipped with organs, limbs, features, and all the other bodily structures found in an adult. In order that the ovum might be transformed into a mature infant, only unfolding and growth were required. After the microscope came into use, however, so simple an explanation could no longer be accepted. Scientists soon realized that the embryo did not exist "ready made" in the ovum, which, even when magnified, failed to bear the faintest likeness to a human being.
Although the microscope made impossible this very simple explanation, it gave in return a truer, if more complex, account of the transformation from egg to offspring. By this means it has been definitely proved that the ovum multiplies rapidly after it has been fertilized, and becomes, as was explained in the preceding chapter, a sac-like structure within which hangs a tiny clump of tissue. This inner mass of cells forms the embryo.
It has proved a difficult task to secure very young human embryos, and many of the ideas we hold relative to the initial stages in the development of man are based upon what has been found true in certain mammals, the class of animals to which we belong. The youngest human ovum known at present has already undergone about two weeks' development, and there the embryo is represented by a flat disk. From this stage to the stage of complete development a satisfactory series of embryos has now been collected, but it is impossible to give here, even in outline, a description of the evolution of the human embryo. No one can understand this intricate subject without the aid of diagrams, models, and other material beyond the reach of all save laboratory workers.
By the end of the second month the development of the embryo has advanced so far that anyone could recognize its human shape. About that time, too, the external sexual organs make their appearance. At first these are quite similar in both sexes; and, if they are used as the criterion, it is possible only toward the end of the third month to say whether the embryo is a male or female.
THE DETERMINATION OF SEX.—The fact that a number of months pass before the sex can be distinguished by an external examination of the fetus has led to the erroneous belief that it can be influenced during the early part of pregnancy or actually determined at will. Various means to accomplish this have been suggested; many of them depend upon modifying the mother's mode of living according as a boy or girl is desired. The most widely known of these doctrines, that of Schenck, was to the effect that the sex of the offspring is always that of the weaker parent. He suggested, therefore, that increasing the vigor of the mother by an appropriate diet would produce a male child, whereas a decrease in her strength would lead to the opposite result. His views, however, were incorrect. After studying extensive statistics Newcomb came to the conclusion that "it is in the highest degree unlikely that there is any way by which a parent can affect the sex of his or her offspring."