/pahr'too rish"euhn, -tyoo-, -choo-/, n. Biol.
the process of bringing forth young.
[1640-50; < LL parturition- (s. of parturitio) travail, equiv. to L parturit(us) (ptp. of parturire; see PARTURIENT) + -ion- -ION]

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Process of bringing forth a child from the uterus, ending pregnancy.

It has three stages. In dilation, uterine contractions lasting about 40 seconds begin 20–30 minutes apart and progress to severe labour pains about every 3 minutes. The opening of the cervix widens as contractions push the fetus. Dilation averages 13–14 hours in first-time mothers, less if a woman has had previous babies. When the cervix dilates fully, expulsion begins. The "water" (amniotic sac) breaks (if it has not already), and the woman may actively push. Expulsion lasts 1–2 hours or less. Normally, the baby's head emerges first; other positions make birth more difficult and risky. In the third stage, the placenta is expelled, usually within 15 minutes. Within six to eight weeks, the mother's reproductive system returns to nearly the prepregnancy state. See also cesarean section; lactation; midwifery; miscarriage; natural childbirth; obstetrics and gynecology; premature birth.
(as used in expressions)

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also called  birth  or  childbirth 

      process of bringing forth a child from the uterus, or womb. The prior development of the child in the uterus is described in the article human embryology. The process and series of changes that take place in a woman's organs and tissues as a result of the developing fetus are discussed in the article pregnancy.

Initiation of labour
      Despite decades of research, the events leading to the initiation of labour in humans remain unclear. It is suspected that biochemical substances produced by the fetus induce labour. In addition, the timing of the production of these substances and their interaction with placental and maternal biochemical factors appear to influence this process. Among the most studied of these biochemical substances are fetal hormones such as oxytocin and placental inflammatory molecules. Increased placental and maternal production of inflammatory molecules in late pregnancy has been strongly linked to the initiation of labour. Hormonelike substances called prostaglandins, which are produced by the placenta in response to various biochemical signals, can induce inflammation and are present in increased levels during labour. Several factors that increase the production of prostaglandins include oxytocin, which stimulates the force and frequency of uterine contractions, and a fetal lung protein called surfactant protein A (SP-A). Surfactant production in the fetal lung does not begin until the last stages of gestation, when the fetus prepares for air breathing; this transition may act as an important labour switch.

The stages of labour

First stage: dilatation
      Early in labour, uterine contractions, or labour pains, occur at intervals of 20 to 30 minutes and last about 40 seconds. They are then accompanied by slight pain, which usually is felt in the small of the back.

      As labour progresses, these contractions become more intense and progressively increase in frequency until, at the end of the first stage, when dilatation is complete, they recur about every three minutes and are quite severe. With each contraction a twofold effect is produced to facilitate the dilation, or opening, of the cervix (uterine cervix). Because the uterus is a muscular organ containing a fluid-filled sac called the amnion (or “bag of waters”) that more or less surrounds the child, contraction of the musculature of its walls should diminish its cavity and compress its contents. Because its contents are quite incompressible, however, they are forced in the direction of least resistance, which is in the direction of the isthmus, or upper opening of the neck of the uterus, and are driven, like a wedge, farther and farther into this opening. In addition to forcing the uterine contents in the direction of the cervix, shortening of the muscle fibres that are attached to the neck of the uterus tends to pull these tissues upward and away from the opening and thus adds to its enlargement. By this combined action each contraction of the uterus not only forces the amnion and fetus downward against the dilating neck of the uterus but also pulls the resisting walls of the latter upward over the advancing amnion, presenting part of the child.

      In spite of this seemingly efficacious mechanism, the duration of the first stage of labour is rather prolonged, especially in women who are in labour for the first time. In such women the average time required for the completion of the stage of dilatation is between 13 and 14 hours, while in women who have previously given birth to children the average is 8 to 9 hours. Not only does a previous labour tend to shorten this stage, but the tendency often increases with succeeding pregnancies, with the result that a woman who has given birth to three or four children may have a first stage of one hour or less in her next labour.

      The first stage of labour is notably prolonged in women who become pregnant for the first time after age 35, because the cervix dilates less readily. A similar delay is to be anticipated in cases in which the cervix is extensively scarred as a result of previous labours, amputation, deep cauterization, or any other surgical procedure on the cervix. Even a woman who has borne several children and whose cervix, accordingly, should dilate readily may have a prolonged first stage if the uterine contractions are weak and infrequent or if the child lies in an inconvenient position for delivery and, as a direct consequence, cannot be forced into the mother's pelvis.

      On the other hand, the early rupturing of the amnion often increases the strength and frequency of the labour pains and thereby shortens the stage of dilatation; occasionally, premature loss of the amniotic fluid leads to molding of the uterus about the child and thereby delays dilatation by preventing the child's normal descent into the pelvis. Just as an abnormal position of the child and molding of the uterus may prevent the normal descent of the child, an abnormally large child or an abnormally small pelvis may interfere with the descent of the child and prolong the first stage of labour.

Second stage: expulsion
      About the time that the cervix becomes fully dilated, the amnion breaks, and the force of the involuntary uterine contractions may be augmented by voluntary bearing-down efforts of the mother. With each labour pain, she can take a deep breath and then contract her abdominal muscles. The increased intra-abdominal pressure thus produced may equal or exceed the force of the uterine contractions. These bearing-down efforts may double the effectiveness of the uterine contractions.

      As the child (fetus) descends into and passes through the birth canal, the sensation of pain is often increased. This condition is especially true in the terminal phase of the stage of expulsion, when the child's head distends and dilates the maternal tissues as it is being born (presentation).

Fetal presentation and passage through the birth canal
 The manner in which the child passes through the birth canal in the second stage of labour depends upon the position in which it is lying and the shape of the mother's pelvis (pelvic girdle). The sequence of events described in the following paragraphs is that which frequently occurs when the mother's pelvis is of the usual type and the child is lying with the top of its head lowermost and transversely placed and the back of its head (occiput (occipital)) directed toward the left side of the mother (see onset of labour in the figure—>). The top of the head, accordingly, is leading, and its long axis lies transversely.

 The force derived from the uterine contractions and the bearing-down efforts exerts pressure on the child's buttocks and is transmitted along the vertebral column to drive the head into and through the pelvis. Because of the attachment of the spine to the base of the skull, the back of the head advances more rapidly than the brow with the result that the head becomes flexed (i.e., the neck is bent) until the chin comes to lie against the breastbone (see flexion in the figure—>). As a consequence of this flexion mechanism, the top of the head becomes the leading pole and the ovoid head circumference that entered the birth canal is succeeded by a smaller, almost circular circumference, the long diameter of which is about 2 centimetres (0.75 inch) shorter than that of the earlier circumference.

 As the head descends more deeply into the birth canal, it meets the resistance of the bony pelvis and of the slinglike pelvic floor, or diaphragm, which slopes downward, forward, and inward. When the back of the head, the leading part of the child, is forced against this sloping wall on the left side, it naturally is shunted forward and to the right as it advances (see internal rotation of head in the figure—>). This internal rotation of the head brings its longest diameter into relation with the longest diameter of the pelvic outlet and thus greatly assists in the adaptation of the advancing head to the configuration of the cavity through which it is to pass.

  Further descent of the head directly downward in the direction in which it has been traveling is opposed by the lower portion of the mother's bony pelvis, behind, and the resisting soft parts that are interposed between it and the opening of the vagina (see internal rotation of head in the figure—>). Less resistance, on the other hand, is offered by the soft and dilatable walls of the lower birth canal, which is directed forward and upward. The back of the child's head accordingly advances along the lower birth canal, distending its walls and dilating its cavity while the head progresses. Soon the back of the child's neck becomes impinged against the bones of the pelvis, in front, and the chin is forced farther and farther away from the breastbone. Thus, as extension (bending of the head backward) takes the place of flexion, the occiput, brow, eye sockets, nose, mouth, and chin pass successively through the external opening of the lower birth canal and are born (see extension in the figure—>).

      The neck, which was twisted during internal rotation of the head, untwists as soon as the head is born. Almost immediately after its birth, therefore, the top of the head is turned toward the left and backward.

 As the child's lower shoulder advances, it meets the sloping resistance of the pelvic floor on the right side and is shunted forward and to the left toward the middle of the pelvis in front. This position brings the long diameter of the shoulder circumference into relation with the anteroposterior, or long diameter, of the pelvic cavity. Because of this internal rotation of the shoulders, the top of the head undergoes further external rotation backward and to the left so that the child's face comes to look directly at the inner aspect of the mother's right thigh (see external rotation of head in the figure—>).

      Soon after the shoulders rotate, the one in front appears in the vulvovaginal orifice and remains in this position while the other shoulder is swept forward by a lateral bending of the trunk through the same upward and forward curve that was followed by the head as it was being born. After this shoulder is delivered, the shoulder in front and the rest of the child's body are expelled almost immediately and without any special mechanism.

      An average of about one hour and 45 minutes is required for the completion of the second stage of labour in women who give birth for the first time. In subsequent labours the average duration of the stage of expulsion is somewhat shorter.

Other fetal presentations

Posterior presentation
      The child may lie so that the back of its head is directed backward and toward either the right or left side. The leading pole is then in the right or left posterior quadrant of the mother's pelvis, and the presentation is referred to as occipitoanterior position. In such cases the back of the child's head usually rotates to the front of the pelvis and labour proceeds as in transverse positions. Because of the longer rotation required, labour may be somewhat more prolonged than in transverse positions.

Face presentation
      When the child's head becomes bent back (extended) so that it enters and passes through the pelvis face first, the condition is known as a face, or cephalic, presentation. The chin is then the leading pole and follows the same course that is followed by the back of the head in occipital presentations. If the chin lies to the front as it enters the pelvis, labour often is easy and of short duration. Should it be directed backward, on the other hand, considerable difficulty may be encountered, and the head may have to be flexed or rotated artificially.

Breech presentation
      Passage of the lower extremities or the buttocks through the pelvis first, called breech presentation, is encountered in 3 to 4 percent of deliveries. Because the head in such cases is the last part of the child to be delivered and because this part of the delivery is the most difficult, the umbilical cord may be compressed while the aftercoming head is being born, with the result that the child may be asphyxiated (asphyxia). Asphyxia or injuries to the child that result from the attendant's effort to hasten the delivery in order to prevent the child's asphyxiation are responsible for the loss of three times as many breech babies as head-on babies. For this reason the child may need to be manipulated into a head-on position by the attendant or be delivered by the surgical procedure called cesarean section.

      The infant mortality rate in developed countries varies from 2 to 10 percent according to the size of the child and skill of the attendant. Because very small premature infants are particularly susceptible to the dangers of breech delivery, the mortality among them is very high when they are born breech first.

      In this relatively rare situation the long axis of the child tends to lie across, or transverse to, the long axis of the mother. Unless the child is very small, delivery through the natural passages is impossible in such cases; therefore, delivery by cesarean section is necessary.

      Because the above-mentioned complications are infrequent and can be cared for easily, the maternal death rate is less than 1 per 1,000 and would be still lower if the deaths caused by complicating systemic diseases were excluded. The infant mortality rate is also low, ranging between 1.5 and 3 percent. It would be much lower if premature and poorly developed infants were excluded. In other words, the risk to a healthy mother who carries her child to maturity is less than 1 per 1,000, and the risk to her mature child is about 0.5 percent.

Third stage: placental stage
 With the expulsion of the child, the cavity of the uterus is greatly diminished (see uterus immediately after birth in the figure—>). As a consequence, the site of placental (placenta) attachment becomes markedly reduced in size, with the result that the placenta (afterbirth) is separated in many places from the membrane lining the uterus. Within a few minutes subsequent uterine contractions complete the separation and force the placenta into the vagina, from which it is expelled by a bearing-down effort. The third stage of labour, accordingly, is of short duration, seldom lasting longer than 15 minutes. Occasionally, however, the separation may be delayed and accompanied by bleeding, in which case surgical removal of the placenta is necessary.

Alfred C. Beck

Relief of pain in labour
      Pain experienced in childbirth can be reduced or relieved by psychoprophylaxis, systemic drugs, regional nerve blocks, or a combination of these methods. One of the first drugs to be used for pain relief was chloroform, which was initially employed in the late 1840s but eventually came into disuse because of its toxicity. In the early 20th century a mixture of scopolamine, an amnesic drug, and morphine was given to produce “twilight sleep.” On awakening from the induced dreamlike state, the woman would have no memory of her labour pains. The desire to be an active participant in the birth experience and to avoid the side effects of delirium and hallucinations led to abandonment of this approach.

      Since first described in the 1930s, psychoprophylaxis has gained in popularity as a method of psychologically and physically preparing a woman for childbirth, thereby helping her to anticipate and cope with the pain of labour (see below Natural childbirth (parturition)). In addition, a comfortable and pleasant environment, supportive friends and family, and a competent and encouraging birth attendant can help to reduce or even eliminate the need for pharmaceutical pain relief. No one method, however, is suited to every woman. Drugs and techniques that are currently in use are described briefly in the following sections (see also drug: Anesthetics (drug)).

Systemic drugs
       meperidine and morphine, given intravenously, are common narcotic drugs used for pain relief (analgesic) ( analgesia) during labour. There are side effects associated with both drugs—namely, nausea and vomiting. When promethazine is given in conjunction with meperidine, these side effects are ameliorated. Other negative maternal effects caused by systemic analgesics are drowsiness, respiratory depression, and lowering of blood pressure (hypotension). Because systemic drugs cross the placental barrier, they can also affect the newborn, causing respiratory depression, decreased alertness, and abnormal reflexes. The longer the duration between the administration of the narcotic and the birth of the child, the higher the level of the drug in the infant and the greater its effects. Another drug commonly used for systemic analgesia is butorphanol, which produces less neonatal depression.

      Barbiturates (barbiturate), once important for lessening labour pains, are now only rarely administered during labour. Although they are sedatives, which normally induce a relaxed state, they are not analgesics and actually may increase sensitivity to pain. Barbiturates also cause respiratory depression in the newborn if administered in active labour, which can be exacerbated by the concomitant use of narcotic analgesics. Sedatives (sedative-hypnotic drug) are used only in the early stages of labour to help the woman relax and rest before the contractions of active labour begin.

Local anesthesia
      Concerns about the negative effects that systemic drugs may have on the mother and newborn have led to heavy reliance on local anesthesia (anesthetic). Local anesthetic agents work by preventing the conduction of nerve impulses. Their actions are limited to nervous tissue located near the injection site, because of their ability to diffuse only short distances. Therefore, local anesthetics numb only an isolated part of the body and allow the woman to retain consciousness, lucidity, and control over the rest of her body.

Epidural block
      The lumbar epidural block has become one of the most popular choices for management of labour pain in the United States. The most common anesthetics used are bupivacaine and lidocaine. When a catheter is used, the advantages of this technique include the ability to modify dose, volume, and type of anesthetic, as appropriate to the stage of labour. If a cesarean delivery becomes necessary, the epidural anesthesia can be extended to provide pain relief for the procedure. Problems associated with a lumbar epidural block include lowering of maternal blood pressure and urinary retention. Because this procedure can slow labour, the hormone oxytocin is often administered concurrently to stimulate uterine contractions.

      Spinal anesthesia (sometimes called spinal block) is produced when a local anesthetic agent, such as lidocaine or bivucaine, sometimes mixed with a narcotic, is injected into the cerebrospinal fluid in the lumbar region of the spine. This technique allows the woman to be awake, while producing extensive numbing of the abdomen, legs, and feet. Because it is a single injection, its duration is limited, generally lasting about two hours, depending on the dose. As a result, spinal anesthesia is typically reserved for cesarean sections or is administered during labour when delivery is expected within two hours. A type of spinal anesthesia called a saddle block anesthetizes the inner thighs, buttocks, and perineum—the parts of the body that in a sitting position would come into contact with a saddle. The numbing effect occasionally extends beyond the intended saddle area, however, reaching as far as the toes. Extreme maternal hypotension, a decrease in utero-placental perfusion, and loss of the urge to push are risks that can accompany spinal anesthesia. These effects, as well as the popularity of more natural childbirth experiences and of epidural block, contributed to a decline in the use of this method.

Pudendal block
      The pudendal block is a relatively simple and common procedure that numbs the birth canal and perineum for spontaneous delivery, forceps delivery, vacuum extraction, and episiotomy. The same anesthetic agents employed in epidural anesthesia are used and are injected through the vagina to the pudendal nerve. This technique relieves the pain from perineal distension but not from uterine contractions.

      In the 1930s Grantly Dick-Read, a British obstetrician, developed a technique of delivery called natural childbirth that minimized the surgical and anesthetic aspects of delivery and concentrated upon the mother's conscious effort to give birth to her child. Although opposed by many physicians who felt that it denied the progress of modern medicine and needlessly primitivized the process of birth, the method was gradually accepted and by the late 1950s was practiced by a sizable percentage of women, especially in the United States and England.

      Natural childbirth—sometimes called psychoprophylaxis, prepared childbirth, or the Lamaze method (Lamaze)—as formulated by Dick-Read and later advanced by Fernand Lamaze, Elizabeth Bing, Robert Bradley, and Charles Leboyer, stems from the premise that childbirth need not be accompanied by excessive pain. It is believed that labour pains are the result of unnatural physical tension caused by fear, which can be counteracted by understanding and by developing the ability to relax. The various methods prescribe for the expectant mother and a partner a lengthy course of instruction in the mechanics of labour and birth as well as exercises to strengthen the musculature and to encourage proper breathing. Emphasis is placed on involving other family members, especially the father, in the birth process. During her labour the mother is aided by trained personnel and her partner, or “coach,” and anesthetic is made available to her when needed. No claims are made that natural childbirth is totally painless; rather it enables the mother's physical response to transcend discomfort.

      Natural childbirth presents the advantage of allowing the woman to participate actively, rather than passively, in labour and to experience the actual moment of birth. The prenatal instruction course also provides women with information about the birthing process, which affords them a greater sense of control over this event.


Operative obstetrics (obstetrics and gynecology)
      Most women deliver a baby spontaneously. However, complications that were present before labour or that develop during labour may threaten the life of the mother or of the baby and may require intervention by the attending physician.

      When a child cannot be delivered through the vagina, it may be necessary to resort to cesarean section, a procedure in which the fetus is delivered through a surgical opening made in the uterus after the uterus has been exposed through an opening made in the abdominal wall. The cesarean section evolved from being a surgical procedure used only in extreme cases and from which the mother rarely recovered to one of the most commonly performed procedures in the United States. Prior to the 20th century, women undergoing a cesarean section usually developed peritonitis and died. Not until the advent of aseptic technique, dependable anesthesia, and proper suturing methods that controlled hemorrhage was the cesarean delivery considered a reasonable alternative to vaginal delivery.

      Cesarean delivery is considered appropriate in various situations in which the risks of vaginal delivery to the fetus or mother are deemed to be greater than the risks from abdominal delivery. Common indications for the procedure include failure of labour to progress, premature delivery for medical reasons, fetal distress, and improper positioning of the fetus for delivery. In addition, cesarean section is often used if the birth canal is too small for vaginal delivery. The procedure is used to avoid further hemorrhage when there is bleeding from placenta praevia (attachment of the placenta to the uterine wall in such a way that it covers the cervix) or from a prematurely separated placenta. If the mother is infected with recurrent genital herpes and lesions are apparent at the time of delivery, a cesarean delivery is usually recommended. It is also resorted to if a woman's blood pressure rises precipitously during labour, as can occur with preeclampsia (although, in general, vaginal delivery is preferable to cesarean delivery for women with preeclampsia). Unusual cases, such as an anomaly of the genitalia or a paralytic muscular disorder that prevents the mother from pushing during labour, will generally require this procedure.

      Maternal complications are still associated with cesarean section. Blood loss, injury to the bowel or bladder, and infection are common risks. Healing of the incision also lengthens recovery. Although the procedure is often done for the benefit of the fetus at risk from asphyxia or trauma resulting from a vaginal birth, there are associated neonatal risks. Infants who have been delivered at various gestational ages sometimes develop respiratory illness. The cause is not completely understood, but the syndrome is most often seen in infants delivered abdominally in the absence of labour. Accidental lacerations of the fetus with the scalpel sometimes occur. Cesarean delivery also is linked with a higher incidence of placenta praevia in future pregnancies.

      In the late 20th century there was concern that cesarean section, although a lifesaving procedure in situations in which either the woman or the child would not have survived delivery otherwise, was becoming overused. From the 1970s, obstetricians increasingly relied on the cesarean birth as an alternative to vaginal birth. The four most frequent reasons cited for performing cesarean sections in the United States were prolonged labour, fetal distress, breech presentation, and previous abdominal delivery. By 2003 roughly 28 percent of women in the United States had cesarean deliveries, which was considered too high because of the risks and complications that the cesarean section itself introduces to delivery. However, safer surgical techniques developed in the early 21st century have greatly reduced the risks traditionally associated with this technique, though there is a general trend in the health care community to encourage vaginal delivery when cesarean sections are not necessary.

Forceps delivery
      Obstetrical forceps are used in vaginal delivery to grasp the fetal head in order to extract the fetus or rotate it so that it is in a satisfactory position for delivery. Some controversy surrounds the use of this procedure, but it is generally agreed that it should be used in situations dangerous to the mother or fetus that could be relieved by prompt delivery. If an expeditious delivery is desired to reduce maternal stress, especially if the woman has heart disease, acute pulmonary edema, or certain neurological conditions or if exhaustion or a prolonged second stage of labour jeopardize a successful vaginal delivery, forceps may be employed. Fetal indications for the use of forceps include prolapse of the umbilical cord, premature separation of the placenta (abruptio placentae), and particular abnormal fetal heart rates. It is important that a certain portion of the fetal head be protruding from the cervix for this technique to be safe for the mother and fetus. Considerable care must be taken to avoid damaging maternal tissues and causing fetal deformation.

      Manual rotation may be used instead of forceps when the fetal head is in an abnormal position that makes delivery difficult or impossible. In carrying out the procedure, the obstetrician's hand is inserted into the birth canal, and the fetal head is turned to a more favourable position.

Vacuum extraction
      The vacuum extractor is a caplike device that is attached by suction to the fetal scalp and is used as an alternative to delivery by forceps. This technique is employed more frequently in Europe than it is in the United States. Cervical and vaginal trauma have occurred in women undergoing this procedure, but it is less severe and less frequent than that experienced with forceps delivery and constitutes the main advantage of vacuum extraction over forceps delivery. Possible fetal complications include damage to the scalp and intracranial hemorrhage.


Complications during labour

      Vaginal lacerations usually manifest as profuse bleeding after delivery of the baby. Not all extensive lacerations cause bleeding, however, and a large tear in the vaginal wall may not be discovered until the health care provider inspects the vagina after the placenta is delivered. There is no difficulty in diagnosing lacerations near the external opening of the birth canal, because they are easily seen by the health care provider. Even minor lacerations are repaired, because, if they are not, granulation tissue may form in the wounds and delay healing. Deep lacerations require surgical reconstruction of the torn tissues. Extensive tears of the perineum (the tissues between the genital organs and the anus) can often be avoided by performing an episiotomy—an incision in the vulvar orifice, the external genital opening—before delivery of the infant's head. Also, attention on the health care provider's part to the mechanism of labour, manual assistance in delivery of the head and shoulders, avoidance of too rapid delivery, delivery between pains, and the proper use of the forceps are some of the many measures that help to avoid injuries not only to the perineum but to all the genital tissues.

      The cervix (uterine cervix), the lower end of the uterus that projects into the vagina, is usually inspected after the placenta has been delivered. Superficial tears look somewhat like a frayed edge on the cufflike cervix. Deeper lacerations usually cause serious bleeding immediately before or after delivery of the placenta, and these lacerations must be repaired promptly. In general, small cervical lacerations are not repaired, since they heal spontaneously. However, deeper tears are sutured. The management of extensive tears into the body of the uterus or the broad ligaments that support the uterus depends on the extent of the injury and its location; abdominal surgery is sometimes required to control bleeding and to repair the uterus. Occasionally hysterectomy—removal of the uterus—is necessary.

Rupture of the uterus
      Rupture of the uterus may occur spontaneously; it may be caused by trauma, or it may occur when a cesarean-section scar gives way. The classical signs of impending spontaneous rupture are gradually increasing, constant, severe pain in the lower part of the abdomen, restlessness, a rising temperature, an increasing pulse rate, and a tense, tender uterus that does not relax between strong contractions. When rupture occurs, the patient complains, usually, of extreme pain and then a sensation of something tearing or giving way. Uterine contractions stop. There is extensive internal bleeding. The baby's body can be felt in the mother's abdomen beside the contracted uterus. Prompt delivery, almost always by cesarean section, is the treatment of impending rupture. The patient is anesthetized to stop uterine contractions as soon as the diagnosis is made.

      Immediate abdominal surgery follows the diagnosis of uterine rupture. Bleeding from the torn uterine walls must be stopped as promptly as possible. The fetus is removed. A hysterectomy is usually performed, because the ragged uterine scar is likely to rupture again if the patient has another term pregnancy, and bleeding from the torn uterus is difficult to control. Such patients often require generous quantities of transfused blood. Antibiotics are given, because infection is, or may be, present.

Uterine prolapse
      Uterine prolapse, or a sliding of the uterus from its normal position in the pelvic cavity, may result from injuries to the pelvic supporting ligaments and muscles that occur during labour. Usually the diagnosis is made months or even years later, when the patient complains of something protruding from the vagina, involuntary loss of urine while coughing or laughing, a sensation of heaviness or discomfort in the pelvic cavity, and difficulty in emptying the lower bowel. The bulging mass formed by a cystourethrocele (protrusion of the bladder and urethra into the vagina) or rectocele (protrusion of the rectum into the vagina), found during a pelvic examination, confirms the diagnosis. Uterine prolapse may be so severe that the uterus lies completely outside the vagina, and the vagina is turned inside out. Treatment depends on the severity of the symptoms; severe prolapse is repaired surgically.

Inversion of the uterus
      Another complication that may occur during labour is inversion of the uterus. The uterus turns inside out and upside down so that its inner surface lies outside and against the wall of the vagina. Inversion causes sudden hypotension and shock, and there may be severe bleeding. The diagnosis is made by noting the uterus, covered by a dark red, bleeding surface, filling or protruding outside the vagina. The placenta may be attached to the uterus.

      Restoration of a uterus to its normal position is accomplished after the patient's shock and hemorrhage are treated and she is anesthetized. The obstetrician inserts a hand into the patient's vagina and lifts up the uterus. The tension applied to the uterine ligaments by this procedure usually reinverts the uterus; if this fails, surgery is necessary.

Embolisms (embolism)
      An embolism is a blockage of a blood vessel, as by a blood clot or bubble of air. Amniotic fluid embolism causes sudden, severe respiratory distress, signs of shock, cyanosis (blueing of the skin), heart collapse, and circulatory failure. If the diagnosis is made promptly, oxygen, blood transfusion, and the injection of fibrinogen, a clotting factor, into a vein may be lifesaving.

       air embolism causes the patient to become suddenly short of breath and cyanotic. She may have heart pain and show signs of shock. The heart beats irregularly, and swishing sounds, caused by the presence of air mixed with blood in the heart, can often be heard. Death follows quickly unless the diagnosis is made at once. Treatment consists of drawing the air from the heart with a needle and syringe.

      Placenta praevia is the implantation of the placenta low in the uterus so that the placenta is close to or partially or completely covering the opening into the cervix. It is suspected if there is painless bleeding during the last three months of pregnancy. The likelihood of the abnormality increases with the number of pregnancies a woman has had and with the rapidity with which one pregnancy follows another. Untreated, the condition may result in early labour, delivery of a premature or stillborn child, and danger of death to the mother from bleeding. Treatment includes control of bleeding and replacement of lost blood by transfusion. Delivery of the infant by cesarean section may be necessary if the mother or the child will be endangered by vaginal delivery. In cases of suspected placenta praevia, the placenta can be located with considerable accuracy by a careful abdominal examination and ultrasonography. In some cases, magnetic resonance imaging (MRI) may be used to confirm diagnosis; however, the long-term effects of fetal exposure to MRI are largely unknown.

      Abnormal adherence of the placenta to the uterus, a condition called placenta accreta, is suspected when the placenta cannot be expelled. Although uncommon, placenta accreta poses serious dangers to the mother. If complicated by coexisting placenta praevia, severe bleeding before labour is common. If placenta accreta arises on the site of a scar from a previous cesarean section, the uterus may rupture during labour. Otherwise, depending on the firmness with which the placenta is anchored, it may be removed surgically after the baby is delivered. If such a removal is unsuccessful, immediate removal of the uterus (hysterectomy) is usually indicated.

Abruptio placentae (placentae abruptio)
      Abruptio placentae is the premature separation of the placenta from its normal implantation site in the uterus. This condition is differentiated from placenta praevia by the fact that the placenta is not in the lower uterine segment. The separation of the placenta causes bleeding, and replacement of the lost blood by transfusion is necessary. The mother may go into shock, and there may be signs of hidden bleeding and concealed blood within the uterus. In instances of complete abruptio placentae, the infant dies unless delivered immediately. In partial separation the mother is given oxygen, and the infant is delivered by cesarean section as soon as it is safe to do so. The cause of abruptio placentae is not known, but it is more common in women who have hypertension.

umbilical cord complications
      A complication of the umbilical cord is suspected when there is marked irregularity in the fetal heart rate and particularly when the irregularity is accentuated by uterine contractions. A prolapsed cord—that is, a cord lying below the head—can be felt through the membranes on vaginal examination. After the membranes have ruptured, the cord can be felt and seen in the vagina. It may hang out of the vulva. The fetus is delivered by cesarean section if the head can be prevented from pressing on the cord while preparations are made for surgery. The baby is delivered vaginally if the cervix is completely dilated and if conditions are favourable for prompt vaginal delivery. Attempts to replace the cord in the uterus are seldom successful.

      True knots in the cord and rupture of the cord with bleeding are seldom diagnosed until after delivery. They are usually associated with sudden and, at the time, inexplicable fetal death.

      Within six to eight weeks after childbirth, most of the structures of the maternal organism that underwent change during pregnancy return more or less to their prepregnancy state. The enlarged uterus, which at the end of gestation weighs about 1,000 grams (35 ounces), shrinks to a weight of about 60 grams (2 ounces). Along with this process of uterine involution, the lining membrane of the uterus is almost completely shed and replaced by a new lining, which is then (six to eight weeks after delivery) ready for the reception of another fertilized ovum (egg).

      The greatly dilated neck of the uterus and lower birth passage likewise undergo marked and rapid involution, but they seldom return exactly to their prepregnancy condition. The markedly stretched abdominal wall also undergoes considerable involution, particularly if abdominal exercises are performed. Although the intradermal tears (striae gravidarum) become smaller and fade, they do not completely disappear but remain as evidence of the marked and rapid stretching of the skin that took place during pregnancy.

John W. Huffman

Additional Reading
Francine H. Nichols and Sharron Smith Humenick, Childbirth Education: Practice, Research, and Theory (1988); Oxorn-Foote Human Labor & Birth, 5th ed. by Harry Oxorn (1986); Helen Varney, Nurse-Midwifery, 2nd ed. (1987). Ed.

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Universalium. 2010.

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