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labor is a topic covered in the Taber's Medical Dictionary.

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(lā′bŏr )

[L., labor, hard work]
In pregnancy, the process that begins with the onset of repetitive and forceful uterine contractions sufficient to cause dilation of the cervix and ends with delivery of the placenta.
SYN: SEE: childbirth; SEE: parturition

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 hr. 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 11/2 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; SEE: 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. Alternatively, 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.

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.

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Venes, Donald, editor. "Labor." Taber's Medical Dictionary, 23rd ed., F.A. Davis Company, 2017. Taber's Online, www.tabers.com/tabersonline/view/Tabers-Dictionary/768640/all/labor.
Labor. In: Venes D, ed. Taber's Medical Dictionary. 23rd ed. F.A. Davis Company; 2017. https://www.tabers.com/tabersonline/view/Tabers-Dictionary/768640/all/labor. Accessed June 18, 2019.
Labor. (2017). In Venes, D. (Ed.), Taber's Medical Dictionary. Available from https://www.tabers.com/tabersonline/view/Tabers-Dictionary/768640/all/labor
Labor [Internet]. In: Venes D, editors. Taber's Medical Dictionary. F.A. Davis Company; 2017. [cited 2019 June 18]. Available from: https://www.tabers.com/tabersonline/view/Tabers-Dictionary/768640/all/labor.
* Article titles in AMA citation format should be in sentence-case
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