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Labor is believed to be triggered by the release of oxytocin and prostaglandins, after a fall in the levels of other hormones. Normally at the end of pregnancy oxytocin, which is stored in the posterior lobe of the pituitary gland, is released and stimulates contraction of the uterine muscles.
The progress and final outcome of labor are influenced by four factors: (1) the “passage” (the soft and bony tissues of the maternal pelvis); (2) the “powers” (the contractions or forces of the uterus); (3) the “passenger” (the fetus); and (4) the “psyche” (mother's emotional state, e.g., anxiety).
The mechanisms of labor (for a vertex presentation) consist of the following sequence of events: engagement (posterior occiput of fetus enters the pelvic outlet); flexion (of fetal head); descent (fetal head descends lower into the midpelvis); internal rotation (fetal head and body rotate so that the occiput is more anterior); extension (fetal head extends once the occiput is beneath the symphysis pubis); and external rotation (fetal head rotates back to position it had at engagement).
This first stage of childbirth is known as the dilatation period. The uterus is like a large rubber bottle with a half-inch long neck that is almost closed. As the uterine muscles contract, the cervix becomes thinner (effacement) and more open (dilated) so that the neck of the uterus eventually resembles that of a jar more than that of a bottle.
The length of the first stage of labor varies with each individual patient, with an average of 8 to 12 hours in primiparous and 6 to 8 hours in multiparous women. It is related to the strength and effectiveness of the contractions and is a period when the mother is instructed to relax as much as possible and let the uterus do the work. Pushing or bearing down is not effective during this stage and is harmful in that it may cause a tearing of the cervix and will only serve to exhaust the woman. She is encouraged to rest and possibly to nap between contractions.
The second stage of labor may be heralded by symptoms of nausea, vomiting, irritability, the urge to bear down, or periods of feeling hot and then cold, signs of the period of transition from the first to the second stage.
During labor the strength, frequency, and duration of contractions are noted and recorded. It is expected that the contractions will increase in all three characteristics, but a sudden change in any one should be reported to the health care provider immediately. The rate, regularity, and volume of the fetal heart tones are checked and recorded periodically. Some apprehensive patients may be helped by allowing them to listen to the infant's heartbeat.
Food and fluids are withheld during active labor, but thirst may cause some discomfort and may be lessened by allowing the patient to moisten her lips with a gauze sponge or to suck on ice chips. Intravenous fluids are usually given. Frequent bathing of the face with a cool washcloth often helps relieve the flushed feeling brought about by the actual hard work being done by the mother. Frequent changing of her gown and of the pad protecting the bed linens may be necessary to keep her clean, dry, and comfortable.
If there is a support person with the woman during labor, that person should be instructed in ways he or she can help the patient and at the same time feel that he or she is making some contribution in this very important event. The support person may wish to participate in keeping a record of the contractions, or might appreciate the opportunity to listen to the fetal heart tones occasionally. If the patient feels that sacral support during each contraction helps mitigate the pain, the support person can be shown how to do this. Some supporters have attended classes for expectant parents and are prepared for their role during labor and delivery. Both the patient and the support person should be informed of the progress during labor so they can feel that something is being accomplished by their efforts.
The patient is encouraged to rest and relax between contractions so as to conserve her strength. She should not bear down until the cervix is fully dilated, since this effort will only serve to exhaust her and may cause lacerations of the cervix. After the cervix is fully dilated she can speed the birth process by holding her breath and contracting her abdominal muscles. Controlled breathing exercises learned in classes for expectant parents promote relaxation and aid labor.
Although serious complications rarely develop during labor, they can occur and must be watched for. Observations to report immediately include hyperactivity of the fetus; vaginal bleeding in excess of a heavy show; a rapid and irregular pulse and drop in blood pressure; sudden rise in blood pressure; and headache, visual disturbances, extreme restlessness, or rapidly developing edema. A sudden cessation of contractions or a contraction that does not relax may indicate a serious disturbance in the labor process. The appearance of meconium in the vaginal discharge may indicate fetal distress unless the infant is in a breech position. (See also fetal monitoring.)
la·bor, stages of labor (lā'bŏr),
labor/la·bor/ (la´ber) [L.] the function of the female by which the infant is expelled through the vagina to the outside world: the first stage begins with onset of regular uterine contractions and ends when the os is completely dilated and flush with the vagina; the second extends from the end of the first stage until the expulsion of the infant is completed; the third extends from expulsion of the infant until the placenta and membranes are expelled; the fourth denotes the hour or two after delivery, when uterine tone is established.
laborParturition Obstetrics The physiologic process that results in the expulsion of a conceptus and placenta from the uterus via the cervix and vagina. See Back labor, False labor, Prechaotic labor, Precipitate labor, Prolonged labor Vox populi Work. See Child labor.
la·bor, stages of labor (lā'bŏr, stājĕz)
labor(la'bor) [L., labor, hard work]
Traditionally, labor is divided into three stages. The first stage of labor, progressive cervical dilation and effacement, is completed when the cervix is fully dilated, usually 10 cm. This stage is subdivided into the latent phase and the active phase.
First stage (stage of dilation): This is the period from the onset of regular uterine contractions to full dilation and effacement of the cervix. This stage averages 12 hr in primigravidas and 8 hr in multiparas.
The identification of this stage is particularly important to women having their first baby. Its diagnosis is complicated by the fact that many women experience false labor pains, which may begin as early as 3 to 4 weeks before the onset of true labor. False labor pains are quite irregular, are usually confined to the lower part of the abdomen and groin, and do not extend from the back around the abdomen as in true labor. False labor pains do not increase in frequency and duration with time and are not made more intense by walking. The conclusive distinction is made by determining the effect of the pains on the cervix. False labor pains do not cause effacement and dilation of the cervix as do true labor pains. See: Braxton Hicks contractions
A reliable sign of impending labor is show. The appearance of a slight amount of vaginal blood-tinged mucus is a good indication that labor will begin within the next 24 hours. The loss of more than a few milliliters of blood at this time, however, must be regarded as being due to a pathological process. See: placenta previa
Second stage (stage of expulsion): This period lasts from complete dilatation of the cervix through the birth of the fetus, averaging 50 min in primigravidas and 20 min in multiparas. Labor pains are severe, occur at 2- or 3-min intervals, and last from a little less than 1 min to a little more than 112 min.
Rupture of the membranes (bag of water) usually occurs during the early part of this stage, accompanied by a gush of amniotic fluid from the vagina. The muscles of the abdomen contract involuntarily during this portion of labor. The patient directs all her strength to bearing down during the contractions. She may be quite flushed and perspire. As labor continues the perineum bulges and, in a head presentation, the scalp of the fetus appears through the vulvar opening. With cessation of each contraction, the fetus recedes from its position and then advances a little more when another contraction occurs. This continues until more of the head is visible and the vulvar ring encircles the head like a crown (therefore often called crowning).
At this time the decision is made concerning an incision in the perineum (episiotomy) to facilitate delivery. If done, it is most commonly a midline posterior episiotomy. When the head is completely removed out of the vagina it falls posteriorly; later the head rotates as the shoulders turn to come through the pelvis. There is usually a gush of amniotic fluid as the shoulders are delivered.
Third stage (placental stage): This is the period following the birth of the fetus through expulsion of the placenta and membranes. As soon as the fetus is delivered, the remainder of the amniotic fluid escapes. It will contain a small amount of blood. Uterine contractions return, and usually within 8 to 10 min the placenta and membranes are delivered. After this, there is some bleeding from the uterus. The amount may vary from 100 to 500 ml.
The amount of blood loss will vary with the size of the fetus, but the average is 200 ml. The probability that blood loss will exceed 500 ml is increased with a large fetus or multiple fetuses, as the placental attachment area on the uterine wall is larger and the uterus is more distended, meaning it does not contract as well after delivery of the fetus, placenta, and membranes. The above probability is less than 5% if the fetus weighs 5 lb (2268 g) or less. Other factors such as episiotomy or perineal laceration will also affect the amount of blood loss. See: birthing chair; Credé method for assisting with the expulsion of the placenta
Often pregnant women and their partners or a labor coach who will be with them attend prenatal classes taught by obstetrical nurses to prepare the patient and family for labor, delivery, and care of the newborn. Such classes include exercises; breathing techniques; supportive care measures for labor, delivery, and the postpartum period; and neonatal care and feeding techniques. Expectant couples (or the pregnant woman and a support person) should attend classes together. The goals of expectant parent education are the birth of a healthy infant and a positive experience for the woman/couple. Labor and delivery may take place in a hospital, birthing center, or at home. Hospitals offer care in traditional labor and delivery rooms and, increasingly, in birthing rooms that simulate a homelike environment. Prenatal records are made available in order to review medical, surgical, and gynecological history; blood type and Rh; and esp. any prenatal problems in the pregnancy. If the mother is Rh negative and if the Rh status of the fetus is unknown or positive, the nurse will administer Rh immune globulin to the mother within 72 hr after delivery.
As part of the admission workup of the laboring woman, the nurse assesses vital signs, height and weight, fetal heart tone and activity, and labor status, i.e., condition of membranes, show, onset time of regular contractions, contraction frequency and duration, and patient anxiety, pain, or discomfort). Initial laboratory studies are carried out according to protocol. The obstetrician, resident physician or other house staff, nurse-midwife, lay midwife, or obstetrical nurse examines the patient, depending on the site and policy. The abdomen is palpated to determine fetal position and presentation (Leopold maneuvers), and a sterile vaginal examination determines cervical dilatation and effacement, fetal station, and position of the presenting part. The attending nurse or midwife monitors and assesses fetal heart rate and the frequency and duration of contractions, using palpation and a fetoscope or electronic monitoring. The frequency of assessment and repetition of vaginal examination are determined by the patient's labor stage and activity and by fetal response. In the past, admission to a labor suite usually included a perineal shave and enema in preparation for delivery, but these procedures have been largely discontinued and are currently done only if prescribed for a particular patient. The patient should urinate and have a bowel movement, if possible. Bladder distention is to be avoided, but catheterization is carried out only if all other efforts to encourage voiding in a patient with a distended bladder fail. The perineum is cleansed (protecting the vaginal introitus from entry of cleansing solutions) and kept as clean as possible during labor. Special cleansing is performed before vaginal examination and delivery, as well as after expulsion of urine or feces.
First stage: The patient may be alert and ambulating, depending on membrane status, fetal position, and labor activity. Electrolyte-rich oral liquids may be prescribed, or intravenous therapy initiated. The nurse supports the patient and her partner or other support person and monitors the progress of the labor and the response of the fetus, notifying the obstetrician or midwife of any abnormal findings. When membranes rupture spontaneously or are ruptured artificially by the midwife or obstetrician, the color and volume of the fluid and the presence of meconium staining or unusual odor are noted. To distinguish it from a sudden spurt of urine having a slightly acid pH, the fluid may be tested for alkaline pH using nitrazine paper. The fetal heart rate, an indicator of fetal response to the membrane's rupture, is noted. Noninvasive pain relief measures are provided, prescribed analgesia is administered as required by the individual patient, and regional anesthetic use is monitored. Patient-controlled epidural anesthesia (PCEA) or continuous epidural anesthesia is frequently employed, based on patient satisfaction regarding its timeliness and effectiveness, and the patient's preference for having pain management under her control.
Second stage: The patient may deliver in any agreed-on position, including lithotomy or modified lithotomy, sitting, or side lying, in a birthing chair, in a birthing bed, or on a delivery table. The nurse, midwife, or physician continues to monitor the patient and fetus; prepares the patient for delivery (cleansing and draping); sets up delivery equipment; and supports the father or support person (positioned near the patient's head), positioning the mirror or TV monitor to permit viewing of delivery by the couple. The nurse also notes and documents the time of delivery, determines the infant’s Apgar score, and provides initial infant care after delivery, including further suctioning of the nasopharynx and oropharynx as necessary (initial suctioning is done by the deliverer before delivering the infant's shoulders), drying and warming the infant (head covering, blanket wrap, or thermal warmer), application of cord clamp (after the deliverer double-clamps the cord and cuts between the clamps), and positive identification (footprints of infant and thumb prints or fingerprints of mother, and application of numbered ankle and wrist band to the infant and wrist band to the mother). Eye prophylaxis for gonorrhea and Chlamydia may be delayed up to 2 hr to facilitate eye contact and to enhance maternal-infant bonding, or may be refused by the parents, on signing of an informed consent. An Apgar score of the infant's overall condition is obtained at 1 min and 5 min after the birth. The infant in good condition is placed on the mother's chest or abdomen for skin to skin contact. This position enhances bonding and maintains infant warmth. Alternately, the infant is put to the breast, and the woman/couple is encouraged to inspect and interact with the infant. An infant in distress is hurried to the nursery, usually with the father or support person attending, so that specialized care can be provided by nursery and neonatal-nurse specialists, and a pediatrician. If the infant is critically ill, its birth may be attended by a chaplain, and photographs may be taken to assist the parents in dealing with the life, critical time, and possible death of the infant.
Third stage: The nurse continues to monitor the status of the patient and the fundus through delivery of the placenta and membranes (documenting the time), examination of the vagina and uterus for trauma or retained products, and repair of any laceration or surgical episiotomy. The placenta is examined to ascertain that no fragments remain in the uterus. The perineal area is cleansed and the mother is assisted to a comfortable position and covered with a warm blanket.
Fourth stage: The nurse continues to observe the patient closely and is alert for hemorrhage or other complications through frequent assessment, including monitoring vital signs, palpating the fundus for firmness and position in relation to the umbilicus at intervals (determined by agency policy or patient condition), and massaging the fundus gently or administering prescribed oxytocic drugs to maintain or assist uterine contraction and to limit bleeding. The character (including presence, size, and number of clots) and volume of vaginal discharge or lochia are assessed periodically; the perineum is inspected and ice applied as prescribed, and the bladder is inspected, palpated, and percussed for distention. The patient is encouraged to void, and catheterization is performed only if absolutely necessary. The nurse notifies the obstetrician or midwife if any problems occur or persist. This period also is used for parent-infant bonding, because the infant is usually awake for the first hour or so after delivery. The mother can breast-feed if she wants to, and the immediate family couple can inspect the infant. The nurse supports the family's responses to the newborn, as well as to the labor and delivery experience. The infant is then taken to the nursery for initial infant care.
Early postpartum period: Once the infant's temperature has stabilized, measurements have been taken (length, head and chest circumference, weight), and other prescribed care carried out, the infant may be returned to the mother's side (in its crib carrier). The nurse continues to assess the mother's physical and psychological status after delivery, checking the fundus, vulva, and perineum according to policy; inspects the mother's breasts and assists her with feeding (whether by breast or bottle) and with measures to prevent lactation as desired; helps the mother to deal with other responsibilities of motherhood; and carries out the mandated maternal teaching program, including providing written information for later review by the patient. In hospitals or birthing centers, the nurse prepares the mother for early discharge to the home setting and arranges for follow-up care as needed and available. In many settings, the nurse makes follow-up calls or visits to the mother during the early postpartum period or encourages her to call in with concerns, or she may receive follow-up visits by a caregiver from her health maintenance organization. The mother may also be referred to support groups, such as the La Leche League, Nursing Mothers' Club, and others as available in the particular community.
artificial laborInduction of labor.
augmented laborInduction of labor.
premature laborPreterm labor
Note: Treatment for active premature labor is best managed in a regional perinatal intensive care center, where staff members are prepared to handle the required care and treatment, and so that the neonate can remain in the same setting as the mother, rather than being transferred alone for neonatal intensive care after delivery.
In-hospital management: The patient is prepared for the use of cardiac, uterine, and fetal monitors along with intravenous therapy. Maternal vital signs and fetal heart rate (FHR) are monitored. If prescribed a tocolytic agent (beta-adrenergic drug) is administered intravenously; the infusion rate is increased every 10 to 30 min, depending on uterine response, but never exceeds a rate of 125 ml/hr. Uterine activity is monitored continuously; vital signs and FHR are checked every 15 min. Maternal pulse should not exceed 140/min; FHR should not exceed 180 bpm. When counting respiratory rate, breath sounds are noted, and the lungs are auscultated at least every 8 hr. The patient is assessed for desired response and adverse effects to treatment and is taught about symptoms she may expect and should report. If signs of drug toxicity occur, the medication is stopped. The intravenous line is kept open with a maintenance solution, and the prescribed beta-blocker as an antidote is prepared and administered. The patient is placed in high Fowler's position, and oxygen is administered. Cardiac rate and rhythm, blood pressure, respiratory rate, auscultatory sounds, and FHRs are closely monitored to evaluate the patient's response to the antidote. If no complications are present, absolute bed rest is maintained throughout the infusion, with the patient in a left-lateral position or supine with a wedge under the right hip to prevent hypotension. Antiembolism stockings are applied, and passive leg exercises are performed. A daily fluid intake of 2 to 3 L is encouraged to maintain adequate hydration, and fluid intake and output are measured. The patient is weighed daily to assess for overhydration. The patient is instructed in methods to deal with stress. Health care providers should respond to parental concern for the fetus with empathy, but never with false reassurance. Fetal fibronectin enzyme immunoassay may be carried out on a sample of vaginal secretions taken from the posterior vaginal fornix; the patient should understand that this test can help assess the risk of preterm delivery within 7 days from the sampling date. As prescribed, a glucocorticoid is administered to stimulate fetal pulmonary surfactant production.
Patients who undergo in-house therapy often receive magnesium sulfate, which helps restore the patient's beta-2 receptor sensitivity (thus improving the effectiveness of terbutaline) and decrease uterine contractions. The patient may be discharged on oral or subcutaneous tocolytic therapy. Intravenous therapy may be employed using a portable micropump that can deliver a basal rate or programmed intermittent bolus doses at predetermined times when the patient's circadian rhythms are known to increase uterine activity.
Home management: The plan for at-home care must target individuals whom the woman can call upon to help with home management. A social service referral can help the family access available community and financial assistance. Home health care nurses assist the patient to carry out the plan, provide ongoing emotional support, and evaluate fetal and patient response to therapy.
The treatment regimen is reviewed with the family, and written instructions are provided to help those involved to cooperate. The patient is maintained on bed rest (left-side, supine, with head on small pillow, feet flat or elevated) to increase uterine perfusion and to keep fetal pressure off the cervix. The patient usually is allowed out of bed only to go to the bathroom. The women's physical and psychological rest are the highest priority, as anxiety is known to compromise uterine blood flow. Paid or voluntary helpers must care for other children and all household chores. The patient's tocolytic therapy (most frequently using terbutaline) is scheduled around the clock (with food if desired), and the patient is taught about its action and adverse effects. The patient must be able to count her pulse, and is instructed to report a rate above 120/min. The patient also is taught about symptoms to report (palpations, tremors, agitation, nervousness) and how to palpate for contractions twice each day. Home uterine activity monitoring may be employed, with the patient or home health care provider recording uterine activity for an hour twice daily. The perinatal nurse analyzes the results. If contractions exceed a predetermined threshold, the patient is advised to drink 8 to 12 ounces of water, rest, then empty her bladder and monitor uterine activity for another hour. The process can reduce unnecessary visits to the medical setting, and increase the patient's peace of mind. The patient is encouraged to drink water throughout the day to prevent dehydration and reduce related uterine irritability. She also is warned not to take over the counter drugs without her obstetrician's approval. The patient is taught how to use sedation, if prescribed. Avoidance of activities that could stimulate labor is emphasized; these include sexual and nipple stimulation. Personal hygiene is reviewed, and the patient is made aware of signs of infection to report. A nonstress test may be performed weekly at home or in a medical setting, depending on the acuity of the situation and on maternal health factors (diabetes, pregnancy-induced hypertension [PIH]). The patient usually is provided with a 24-hr phone link to perinatal nurses in the health care system, who may contact her twice daily to discuss her situation. She is taught what to do in an emergency (bright red bleeding, membrane rupture, persisting contractions, decreased or absent fetal activity). If an incompetent cervix has been diagnosed based on the patient’s history, insertion of a purse-string suture (cerclage) as reinforcement at 14 to 18 weeks gestation may prevent premature labor. If labor is inevitable, it is carried out as for a low-birth-weight, readily compromised fetus. During the postpartum period, care focuses on helping the family to understand their infant's special needs, and to participate as fully as possible in care, or, in a worst-case scenario, to come to terms with the baby's death. In such a case, the family is assisted in their grieving, with encouragement to hold the swaddled infant, and look at pictures of the child if they are able. Psychological counseling may be required.
primary dysfunctional laborprotracted labor.
prolonged latent phase labor
See: arrested labor; precipitate labor