Difficult labor is uncommon today. Its lessened frequency in modern childbirth stems from prevention, sorting out probable cases and delivering them by Cesarean section before labor’s onset, and from the fact that there are many therapeutic measures which can be employed to prevent a labor from becoming difficult. Such measures are the stimula- tion of weak contractions by drugs, the inducement of rest during labor through sedation, the administration of glucose solution into an arm vein to eliminate dehydration, and the prevention of infection by antibiotics. But even granting the premise that the chance of having a difficult labor is slim, no discussion of birth would be complete without its inclusion.
Dystocia (Greek ‘difficult’ + ‘birth’) has many causes. These can be classified under three headings: abnormalities of the expulsive forces, of the passenger, or of the passage.
The first of these, abnormality of the expulsive forces, is termed inertia of the uterus—that is, poor pains. They may be too short, too feeble, too infrequent, or, as is usual, a combination of all three. The labor pains may be subnormal throughout the travail (primary inertia) or normal at first and then become desultory (secondary inertia). Drugs to stimulate labor, like Pitocin, are used in exceedingly small amounts to treat inertia. Usually it is given as a constant infusion in an arm vein, a little of the drug being diluted 500 or 1000 times with glucose water. When a Pitocin drip is started, it is likely to be continued until after the delivery. A very new drug, Spartine, may be used in place of Pitocin. It is usually injected into an arm muscle every forty minutes. Strong pains often follow these wonderful aids to labor.
Contrary to expectation, the patient’s physical condition at the onset of labor seems to have no influence on the character of the pains. Patients debilitated by wasting disease to the point of complete invalidism have as strong pains as the most robust
It seems wise at this point to continue to lay the ghost of dry labors. For some reason laymen and physicians alike have the idea that dry labors per se are longer, more painful, and more dangerous than labors with intact membranes. This is not true, according to several investigations. All agree that, if everything else is normal, not only is there no injurious effect from the premature rupture of the membranes, but it actually exerts a beneficial influence on the length of labor.
Abnormalities of the Passenger
The second source of dystocia is abnormality of the passenger, the. The most common complications in this respect are abnormalities of position and size. The normal position of the fetus during labor is with the head down, the breech up, the spinal column parallel to the long axis of the mother, and the back of the baby facing forward toward the mother’s abdominal wall. The head is flexed so that the baby’s chin practically rests on its breastbone. Labor in the average case is lengthened somewhat by the two most common variations from normal fetal position—posterior presentations and breech presentations. In the former, the baby presents head first, but its back faces the back of the mother instead of her abdomen, and the length of labor is often increased. In a breech presentation, where the child presents with the breech down and the head up, the average duration of the labor is increased about one hour. The less common abnormalities of position—transverse (the long diameter of the child and that of the mother being at right angles), face (the head, instead of being completely flexed or bowed as usual, is extended so that the face presents to the pelvic inlet instead of the crown of the head), and brow (the head flexed only partially so that the forehead presents)—lengthen labor more than one hour. Strange as it may seem, the weight of the baby appears to have no effect on multiparous labors but exerts an appreciable one on the labor of primiparas. A first labor with a nine-pound baby is usually two and one-half hours longer than a first labor with a five-and-one-half-pound baby.
Abnormalities of the Passage
The third source of dystocia lies in abnormalities of the passage, the birth corridor, which includes the bony pelvis as well as soft tissues, the cervix and vagina.
The bony pelvis is roughly funnel-shaped—the child enters the circular mouth of the funnel (pelvic inlet) and issues forth from the spout (pelvic outlet). If any diameter of the pelvis is diminished below the limit of ordinary normal variations we classify the pelvis as contracted. The type of contraction depends, first, on the particular diameter affected and, second, on the cause.
Our modern concept of the obstetrical pelvis and its measurement (pelvimetry) dates from the middle of the last century, when two professors in Kiel each carefully measured the pelves of a thousand German women, and in this way established what measurements cause a pelvis to be classified as normal, borderline, or contracted.
Indications of pelvic size can be gathered from the patient’s history, by manual measurements, by how far the baby has already descended when labor commences, and by the labor’s course.
It is obvious that when a woman has given birth successfully to a nine-pound baby in a previous labor one may be quite certain she has a normal, capacious pelvis. The reverse may also be significant. If the birth of a five- or six-pound baby was attended with difficulty it is quite possible that the pelvis is small.
At the pelvic examination during the first prenatal visit the obstetrician takes a key measurement for the estimation of pelvic size. He measures the diagonal conjugate (C. D.), the distance from the under surface of the symphysis bone in front to the top of the sacrum (the posterior bony wall of the pelvis) where it joins the last vertebra, as felt on vaginal examination. If the measurement is five inches or longer, one can almost be certain that the upper part of the pelvis, the pelvic inlet, is not contracted. He also feels vaginally the general shape and contour of the bony pelvis, particularly to determine whether its lowermost portion is ample in size.
In a first pregnancy, by the time labor commences at term the part of the baby presenting, the head or breech, should be engaged—that is, it already should have descended well into the pelvic inlet, the mouth of the bony funnel. Lack of engagement at the onset of labor in births subsequent to the first does not suggest a contracted pelvis.
If after several hours of adequately strong labor there is little evidence of progress in either the baby’s descent or dilatation of the cervix, the properly trained physician will reconsider his previous favorable estimate of pelvic size.
Whenever for any reason, the physician is suspicious of the adequate size of the pelvis, he has available an excellent technique for confirming or refuting these suspicions, X-ray pelvimetry.
Only by X-ray pelvimetry can the internal diameters of the pelvis be measured with precision. Numerous techniques are in use, and roentgenologists have individual preferences. All of the standard methods are satisfactory when scrupulous attention is paid to technical details such as the positioning of the patient and the distance of the X-ray tube from the film. Ordinarily two pictures are taken: a front view from which one can measure the transverse diameters of the pelvis, and a lateral view from which the longitudinal diameters are read.
The experienced physician is not only able to obtain precise measurements of crucial pelvic diameters from X-ray pelvimetry but he also gains an understanding of the pelvic architecture which offers him valuable guidance in a problem case. He can determine whether the inlet is round, heart-shaped, narrowed like a tennis court, or elliptical; he can see whether the walls of the pelvis tend to converge or diverge; and he can study the form of the sacrum. It may be important to know whether it is straight or curved, and whether it flares back or forward.
If, because of a previous bad obstetric history or subnormal manual measurements, the physician determines at the patient’s first visit to obtain X-ray pelvimetry, he will undoubtedly postpone the procedure until about the thirty-sixth week of pregnancy. The postponement is motivated by his desire to eliminate the purely theoretical danger of exposing the very early fetus to Roentgen rays, but, more important, it permits a meaningful comparison between the pelvic diameters and those of the fetal skull. On the other hand, if X-ray pelvimetry is not decided upon until after labor commences, it can be done with equal satisfaction at this time.
Large, modern maternity hospitals, like the one at the Mount Sinai Hospital, have an X-ray unit as part of the delivery-floor equipment. It can render valuable assistance. For example, in a case of dystocia, the mother was a twenty-eight-year-old woman in her first pregnancy. She was found to have a small pelvis on manual measurement, which was confirmed at the thirty-sixth week by X-ray pelvimetry. Labor started early in the morning in the thirty-eighth week of pregnancy. The baby seemed smaller than average, so it was determined to allow a trial of labor. In order to determine precisely the extent of progress, additional X-rays were taken at noontime. Their study revealed that the baby’s head was undergoing a physiologic, harmless process of molding from its compression within the mother’s bony pelvis. The molding was causing the head to narrow and at the same time lengthen. Since the pelvis was contracted only at the inlet, the rest being very roomy, it was obvious that if the fetal head could mold sufficiently to pass through the bony ‘narrows’ the baby could fall out. Two hours later it virtually did; the patient had a simple spontaneous delivery of a seven-pound baby with an unattractively elongated head which was perfectly rounded within three days.
In reality there is no straightforward entity such as a contracted pelvis or a normal pelvis. The true issue is whether or not Mrs. Jones’s pelvis is large enough to deliver successfully baby Jones, with whom she will labor or is laboring. A pelvis technically contracted may be functionally normal, or a technically normal pelvis may be functionally contracted, as in the case of a woman with small but normal pelvic measurements who labors with an eleven-pound infant. Therefore in each labor one attempts to judge the size of the baby in relation to the size of the pelvis. If the baby is big and the pelvis small, examination demonstrating true disproportion between the two, unsuccessful labor is obviated by Cesarean section a few days before the due date or early in the labor. However, if there is uncertainty about the possibility of a vaginal delivery, a test of labor is called for, which harms neither mother nor baby. Today such test labors are rarely allowed to last more than eight or ten hours; if at the end of the test period little progress has been made, a Cesarean section is performed. On the other hand, if the presenting part has descended and the cervix is dilating satisfactorily, labor is permitted to continue with full anticipation of a normal birth.
The baby’s head is extremely malleable, since the bones forming the skull are still separated, not having fused together as they will by the age of eighteen months. Molding of the head by the forces of labor is very gradual, the head acting as though made of very stiff clay. Molding may make a big difference—the head may gradually decrease a half-inch or more in a critical diameter during several hours of labor. When a baby comes breech first, the aftercoming head is born without the opportunity to mold. Therefore larger pelvic diameters are required to accommodate a breech birth than when the baby exits head first. Because of this, many physicians make it routine to secure X-ray pelvimetry in all breech cases, particularly in first labor.
CAUSES OF CONTRACTED PELVES
Contracted pelves are due to heredity or environment. The generally contracted variety usually occurs in undersized, small-boned, fragile-looking women. In them it is largely an inherited stigma. General malnutrition and poor hygiene during the years of growth may exaggerate this in- herited pattern. A typical generally contracted pelvis is about four-fifths the size of the normal pelvis.
Individuals in whom the inherited reduction in height is decidedly more marked than is seen in small normal people are classed as dwarfs.
Dwarfs present an interesting obstetrical problem. Medically we distinguish two types of inherited dwarfism: the true ateliotic (Greek: ‘not’ + ‘complete’) dwarf, a properly proportioned individual who differs from the normal only in his miniature appearance; and the chondrodystrophic (Greek: ‘cartilage’ + ‘ill’ + ‘nutrition’) dwarf, an individual with very short arms and legs and a normal-sized head and trunk. Circus troupes contain both types.
The ateliotic rarely have children, but the short-limbed chondrodystrophic, so faithfully depicted by Velazquez, presents a very real obstetrical problem, since both sexes are normally fertile. This type of dwarfism narrows the pelvic inlet and, since the children are of normal size, dystocia invariably results. Before the modern surgical era and its relatively safe Cesarean operation, chondrodystrophic women rarely survived pregnancy. Today, of course, the chances for a live mother and a live infant are excellent. A chondrodystrophic parent of either sex may have normal children; in fact, this is usually the case, although there is no doubt that the deformity is more common in certain stocks tainted by it.
Rickets and Osteomalacia
Rickets and osteomalacia (Greek: ‘bone’ + ‘softness’) are the two environmental conditions which cause the greatest distortion and contraction of the pelvis. Rickets, a disease of infancy, is due to dietary deficiencies of calcium, phosphorus, and Vitamin D, and at the same time a subnormal quantity of the ultra-violet rays from sunlight. Therefore it is mainly an urban disease, for though rural children may have rickets-producing diets, they get enough sunlight to compensate. It is a disease for which the colored races have a special predisposition since their skin pigment makes it more difficult for the ultra-violet rays to penetrate.
In a severe case the whole skeleton of the infant becomes soft and putty-like. Arms and legs bow; the spinal column becomes bent and angulated; and the ribs become beaded where they join the breastbone (the rickety rosary). At the same time the forehead protrudes on either side (rachitic bossae) and the pelvis becomes narrowed. A rachitic infant delays its walking because of pain in standing on its softened limbs; as a result, it spends its waking hours sitting. The whole weight of the upper body, transmitted down the spinal column, constantly presses upon the putty-like sacrum (the large bone that forms the base of the spinal column and the rear of the pelvic girdle); this makes the sacrum buckle forward, reducing the most important diameter of the pelvic inlet. In severe cases this diameter is so diminished that it offers an insuperable barrier to vaginal delivery. The lower portion of the pelvis, the pelvic outlet, is not contracted in rickets; as a matter of fact it is often widened, since the constant sitting posture of the child tends to spread apart the softened bones.
Osteomalacia, adult rickets, is unknown in this country but flourishes in northern China and in certain parts of India. In the latter country it is intimately associated with the folk custom that decreed permanent indoor seclusion for the women of certain classes.
Unlike rickets, osteomalacia contracts the outlet as well as the inlet of the pelvis—the spout of the funnel as well as the bowl.
Both rickets and osteomalacia are best treated by prevention. A well-balanced diet, cod-liver oil or other substances rich in Vitamin D, and abundant sunshine during childhood and pregnancy make their acquisition virtually impossible. I am happy to say that during my medical lifetime rickets has almost disappeared from the American scene, a tribute to our efficient public-health agencies. This makes a striking contrast to thirty years ago, when I assisted at, or performed, many Cesarean sections because of rachitic pelvic deformities. Today there are few if any such cases in all New York.
In rare instances, despite strong pains, a normal pelvis, an average-sized infant, and a satisfactory position of the fetus, the cervix dilates with abnormal tardiness. These cases are spoken of as instances of cervical dystocia. Some of them follow previous operations or treatments of the cervix, while others show no discoverable cause. Cervical dystocia may prolong labor many hours, and even then the very last stages of dilatation may have to be completed by some operative means. Treatment consists of patience on the part of patient and physician, to say nothing of patience on the part of the family.
Resistant vaginal tissues may prolong the second stage, the time intervening from the full dilatation of the cervix to the birth of the child. This is especially common in comparatively elderly primiparas, women aged thirty-five or more, in their first labor. Strenuous athletic pursuits, especially horseback riding, thicken vaginal muscles, and this occasionally produces a soft-tissue dystocia. From this point of view—and from only this one viewpoint—the thin, emaciated, sedentary type of woman has an obstetrical advantage over her robust, muscular, athletic sister. Dystocia from unusually resistant vaginal tissues can be easily overcome by an episiotomy—cutting of the tissues.
The author is constantly aware that a lay reader may have a tendency to overemphasize and personalize anything which smacks of the abnormal in birth. Instead of taking the cheerful attitude that the abnormal is the infrequent—an attitude which would be fully justified by facts—she says to herself, ‘It would be just my luck to have a tough time.’
More than ninety-five out of a hundred readers will not They will be pleasantly surprised to discover how easy and simple the whole process is. To the remaining five or less we can give comfort by assuring them honestly that modern obstetrics accepts the challenge of the abnormal with glee, since it finds no abnormality beyond the reach of the knowledge and tools now available to it.