AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

DEFINITION

Section 2 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

Labor is a physiologic process during which the products of conception (ie, the fetus, membranes, umbilical cord, and placenta) are expelled outside of the uterus. Labor is achieved with changes in the biochemical connective tissue and with gradual effacement and dilatation of the uterine cervix as a result of rhythmic uterine contractions of sufficient frequency, intensity, and duration (American College of Obstetricians and Gynecologists [ACOG], 2003; Norwitz, 2003).

Labor is a clinical diagnosis. The onset of labor is defined as regular, painful uterine contractions resulting in progressive cervical effacement and dilatation. Cervical dilatation in the absence of uterine contraction suggests cervical incompetence, whereas uterine contraction without cervical change does not meet the definition of labor.

For excellent patient education resources, visit eMedicine's Pregnancy and Reproduction Center. Also, see eMedicine's patient education articles Labor Signs, Pregnancy, and Cesarean Childbirth.

STAGES OF LABOR AND EPIDEMIOLOGY

Section 3 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

Stages of labor

Obstetricians have divided labor into 3 stages that delineate milestones in a continuous process.

First stage of labor

The first stage begins with regular uterine contractions and ends with complete cervical dilatation at approximately 10 cm. In his landmark studies of 500 nulliparas, Friedman (1955) subdivided the first stage into an early latent phase and an ensuing active phase. The latent phase describes the period between the onset of labor and when the rate of cervical dilatation changes most rapidly, usually at about 3-4 cm of cervical dilatation. The active phase heralds a period of increased rapidity of cervical dilation and ends with complete cervical dilation of 10 cm. According to Friedman, the active phase is further divided into an acceleration phase, a phase of maximum slope, and a deceleration phase.

Characteristics of the average cervical dilatation curve is known as the Friedman curve, and a series of definitions of labor protraction and arrest were subsequently established (Friedman, 1961 and 1961). However, subsequent data suggest that the rate of cervical dilatation is slower and the progression of labor may be significantly different from that shown on the Friedman curve (Kilpatrick, 1989; Albers, 1996; Zhang, 2002).

Second stage of labor

The second stage begins with complete cervical dilatation and ends with the delivery of the fetus. The ACOG has suggested that a prolonged second stage of labor should be considered when the second stage exceeds 3 hours if regional anesthesia is administered or 2 hours in the absence of regional anesthesia in nulliparas. In multiparous women, such a diagnosis can be made if the second stage of labor exceeds 2 hours with regional anesthesia or 1 hour without it (ACOG, 2003).

Studies performed to examine perinatal outcomes associated with a prolonged second stage of labor revealed increased risks of surgical deliveries and maternal morbidities but no differences in neonatal outcomes (Menticoglou 1995; Janni, 2002; Cheng, 2003; Myles, 2003). Maternal risk factors associated with a prolonged second stage include nulliparity, maternal weight and/or weight gain, use of regional anesthesia, induction of labor, fetal occiput in a posterior position, and increased birthweight (Cheng, 2003; Myles 2003; O'Connell, 2003; Senécal, 2005).

Third stage of labor

The third stage of labor lasts from the delivery of the fetus until the delivery of the placenta and fetal membranes. Although delivery of the placenta requires less than 10 minutes, the duration of the third stage of labor may last as long as 30 minutes before active intervention is commonly considered (Norwitz, 2003).

Epidemiology

The childbearing population in the United States has changed, and the clinical obstetric management of labor also has evolved since Friedman's studies. Data from number a studies (Kilpatrick, 1989; Albers, 1996; Zhang, 2002) have suggested that normal labor can progress at a rate much slower than that Friedman and Sachtleben had described (1961). Zhang et al (2002) examined the labor progression of 1162 nulliparas who presented in spontaneous labor and constructed a labor curve that was markedly different from Friedman's: The average interval to progress from 4-10 cm of cervical dilatation was 5.5 hours compared with 2.5 hours of Friedman's labor curve. Kilpatrick et al (1989) and Albers et al (1996) also reported that the median lengths of first and second stages of labor were longer than those Friedman suggested.

Furthermore, data suggest that a number of factors are associated with the length of labor. One group reported that increasing maternal age associated with a prolonged second stage but not first stage of labor (Rasmussen, 1994).

Some authors have observed that the length of labor differs among racial groups. One group reporting that Asian women have the longest first and second stages of labor compared with Caucasian or African American women (Tuck, 1983), and American Indian women had second stages shorter than those of non-Hispanic Caucasian women (Albers, 1996). However, others report conflicting findings (Duignan, 1975; Sills, 1997). Differences in the results may have been due to variations in study designs, study populations, labor management, or statistical power.

In 1 large retrospective study of the length of labor, specifically with respect to race and/or ethnicity, investigators observed no significant differences in the length of the first stage of labor. However, the second stage was shorter in African American women than in Caucasian women for both nulliparas (-22 min) and multiparas (-7.5 min). Hispanic nulliparas, compared with their Caucasian counterparts, also had a shortened second stage, whereas no differences were seen for multiparas. In contrast, Asian nulliparas had a significantly prolonged second stage compared with their Caucasian counterparts, and no differences were seen for multiparas (Greenberg, In press).

MECHANISM OF LABOR, OR CARDINAL MOVEMENTS

Section 4 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

The ability of the fetus to successfully negotiate the pelvis during labor involves changes in position of its head during its passage in labor. The mechanisms of labor, also known as the cardinal movements, are described in relation to a vertex presentation, as is the case in 95% of all pregnancies. Although labor and delivery occurs in a continuous fashion, the cardinal movements are described as 7 discrete sequences, as discussed below (Norwitz, 2003).

Engagement

The widest diameter of the presenting part (with a well-flexed head, where the largest transverse diameter of the fetal occiput is the biparietal diameter) enters the maternal pelvis to a level below the plane of the pelvic inlet. On the pelvic examination, the presenting part is at 0 station, or at the level of the maternal ischial spines.

Descent

The downward passage of the presenting part through the pelvis. This occurs intermittently with contractions. The rate is greatest during the second stage of labor.

Flexion

As the fetal vertex descents, it encounters resistance from the bony pelvis or the soft tissues of the pelvic floor, resulting in passive flexion of the fetal occiput. The chin is brought into contact with the fetal thorax, and the presenting diameter changes from occipitofrontal (11.0 cm) to suboccipitobregmatic (9.5 cm) for optimal passage through the pelvis.

Internal rotation

As the head descends, the presenting part, usually in the transverse position, is rotated about 45° to anteroposterior (AP) position under the symphysis. Internal rotation brings the AP diameter of the head in line with the AP diameter of the pelvic outlet.

Extension

With further descent and full flexion of the head, the base of the occiput comes in contact with the inferior margin of the pubic symphysis. Upward resistance from the pelvic floor and the downward forces from the uterine contractions cause the occiput to extend and rotate around the symphysis. This is followed by the delivery of the fetus' head.

Restitution and external rotation

When the fetus' head is free of resistance, it untwists about 45° left or right, returning to its original anatomic position in relation to the body.

Expulsion

After the fetus' head is delivered, further descent brings the anterior shoulder to the level of the pubic symphysis. The anterior shoulder is then rotated under the symphysis, followed by the posterior shoulder and the rest of the fetus.

CLINICAL HISTORY AND PHYSICAL EXAMINATION

Section 5 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

History

The initial assessment of labor should include a review of the patient's prenatal care, including confirmation of the estimated date of delivery. Focused history taking should be conducted to include information, such as the frequency and time of onset of contractions, the status of the amniotic membranes (whether spontaneous rupture of the membranes has occurred, and if so, whether the amniotic fluid is clear or meconium stained), the fetus' movements, and the presence or absence of vaginal bleeding.

Braxton-Hicks contractions, which are often irregular and which do not increase in frequency with increasing intensity, must be differentiated from true contractions. Braxton Hicks contractions often resolve with ambulation or a change in activity. However, true labor contractions tend to be long and intense, and they tend to lead to cervical change. True labor is defined as uterine contractions leading to cervical changes. If contractions occur without cervical changes, it is not true labor. Other causes for the cramping should be diagnosed. Gestational age is not a part of the definition of labor.

In addition, Braxton-Hicks contractions occur occasionally, usually no more than 1-2 per hour, and they often occur just a few times per day. Labor contractions are persistent, they may start as infrequently as every 10-15 minutes, but they accelerate over time, increasing to 1 every 2-3 minutes.

Patients may also describe what has been called lightening, ie, physical changes felt because the fetus' head is advancing into the pelvis. The mother may feel that her baby has become light or that it as started to drop, and the shape of her abdomen may change to reflect descent of the fetus. Her breathing may be relieved because tension on the diaphragm is reduced, whereas urination may become frequent because of added pressure on the bladder.

Physical examination

Physical examination should include documentation of the patient's vital signs, the fetus' presentation, and the fetus' wellbeing. The frequency, duration, and intensity of uterine contractions should be assessed. Be particularly alert when performing abdominal and pelvic examinations in patients who present in possible labor.

Abdominal examination begins with the Leopold maneuvers described below (Norwitz, 2003):

• The initial maneuver involves the examiner placing both of his or her hands on each upper quadrant of the patient's abdomen and gently palpating the fundus with the tips of the fingers to define which fetal pole is present in the fundus. If it is the fetus' head, it should feel hard and round. In a breech presentation, a large, nodular body is felt.
• The second maneuver involves palpation in the paraumbilical regions with both hands by applying gentle but deep pressure. The purpose is to differentiate the fetal spine (a hard, resistant structure) from its limbs (irregular, mobile small parts) to determinate the fetus' position.
• The third maneuver is suprapubic palpation by using the thumb and fingers of the dominant hand. As with the first maneuver, the examiner ascertains the fetus' presentation and estimates its station. If the presenting part is not engaged, a movable body (usually the fetal occiput) can be felt. This maneuver also allows for an assessment of the fetal weight and of the volume of amniotic fluid.
• The fourth maneuver involves palpation of bilateral lower quadrants with the aim of determining if the presenting part of the fetus is engaged in the mother's pelvis. The examiner stands facing the mother's feet. With the tips of the first 3 fingers of both hands, the examiner exerts deep pressure in the direction of the axis of the pelvic inlet. In a cephalic presentation, the fetus' head is considered engaged if the examiner's hands diverge as they trace the fetus' head into the pelvis.

Pelvic examination is performed in a sterile fashion to decrease the risk of infection. Use of sterile gloves is preferred. If membrane rupture is suspected, examination with a sterile speculum is performed to visually confirm pooling of amniotic fluid in the posterior fornix. The examiner also looks for fern on a dried sample of the vaginal fluid under a microscope and checks the pH of the fluid by using a nitrazine stick or litmus paper, which turns blue if the amniotic fluid is alkalotic. If frank bleeding is present, pelvic examination should be deferred until placenta previa is excluded with ultrasonography. Furthermore, the pattern of contraction and the patient's presenting history may provide clues about placental abruption.

Digital examination of the vagina allows the clinician to determine the following: (1) the degree of cervical dilatation, which ranges from 0 cm (closed or fingertip) to 10 cm (complete or fully dilated), (2) the effacement (assessment of the cervical length, which is often reported as a percentage of the normal 3- to 4-cm-long cervix), (3) the position, ie, anterior or posterior, and (4) the consistency, ie, soft or firm. Palpation of the presenting part of the fetus allows the examiner to establish its station, by quantifying the distance of the body (-5 to +5 cm) that is presenting relative to the maternal ischial spines, where 0 station is in line with the plane of the maternal ischial spines) (Norwitz, 2003).

The shape of the mother's pelvis can also be assessed and classified into 4 broad categories based on the descriptions of Caldwell and Moloy (1933): gynecoid, anthropoid, android, and platypelloid. Although the gynecoid and anthropoid pelvic shapes are thought to be most favorable for vaginal delivery, many women can be classified into 1 or more pelvic types, and the distinctions can be arbitrary (Norwitz, 2003).

WORKUP

Section 6 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

High-risk pregnancies can account for up to 80% of all perinatal morbidity and mortality. The remaining perinatal complications arise in pregnancies without identifiable risk factors for adverse outcomes (Friedman, 1967). Therefore, all pregnancies require thorough evaluation and close surveillance. As soon as the mother arrives at the labor and delivery suite, external tocometric monitoring for the onset and duration of uterine contractions and use of a Doppler device to detect fetal heart tones and rate should be started.

If a laboring mother has ruptured membranes, an intrauterine pressure catheter can be inserted past the fetus into the uterus to best determine the onset and the duration if the external tocometer does not detect contractions because of patient factors (eg, obesity). Because the external tocometer records only the timing of contractions, an intrauterine pressure catheter can be used to measure the pressures generated during uterine contractions if their strength or adequacy is a concern.

If worrisome tracings (eg, late decelerations) are noted on the fetal heart rate monitor, a fetal scalp electrode may be applied to generate sensitive readings of beat-to-beat variability. Avoid attaching a fetal scalp electrode if the mother has HIV, hepatitis B, or hepatitis C infections or if fetal thrombocytopenia is suspected.

Further evaluation of a distressed fetus can be accomplished with blood sampling from fetal scalp capillaries. This procedure allows for a direct assessment of fetal oxygenation and blood pH. A pH of <7.20 warrants further investigation for the fetus' well-being and for possible resuscitation or surgical intervention.

Routine laboratory studies, such as CBC analysis, blood typing and screening, and urinalysis, are usually performed. Intravenous (IV) access is established.

INTRAPARTUM MANAGEMENT OF LABOR

Section 7 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

First stage of labor

Cervical change occurs at a slow, gradual pace during the latent phase of the first stage of labor. According to Friedman (1955) and Friedman and Sachtleben (1961), the rate of cervical dilation should be at least 1 cm/h in a nulliparous woman and 1.2 cm/h in a multiparous woman during the active phase of labor. However, labor management has changed substantially during the last quarter century, and the induction of labor, the augmentation of labor, the use of regional anesthesia for pain control, and fetal heart rate monitoring are common practice. Vaginal breech and mid- or high-forceps deliveries are rarely preformed. Therefore, subsequent authors have suggested normal labor may precede at a rate less rapid than those previously described (Kilpatrick, 1989; Albers, 1996; Zhang, 2002).

On admission to the labor and delivery suite, a woman having normal labor should be encouraged to assume the position that she finds most comfortable. Possibilities including walking, lying supine, sitting, or resting in a left lateral decubitus position. Of note, ambulating during labor did not change the progression of labor in a large randomized controlled study of >1000 women in active labor (Bloom, 1998).

The patient and her family or support team should be consulted regarding the risks and benefits of various interventions, such as the augmentation of labor of oxytocin, artificial rupture of the membranes, methods and pharmacologic agents for pain control, and surgical vaginal or cesarean delivery. They should be actively involved, and their preferences should be considered in the management decisions made during labor and delivery (Norwitz, 2003).

The frequency and strength of uterine contractions and changes in cervix and in the fetus' station and position should be assessed periodically to evaluate the progression of labor. Although progression must be monitored, vaginal examinations should be preformed only when necessary to minimize the risk of chorioamnionitis, particularly in women whose amniotic membrane has ruptured. During the first stage of labor, fetal well-being can be assessed by monitoring the fetal heart rate at least every 15 minutes, particularly during and immediately after uterine contractions. In most labor and delivery units, the fetal heart rate is assessed continuously (ACOG, 2005).

Two methods of augmenting labor have been established. The traditional method involves the use of low doses of oxytocin with long intervals between dose increments. For example, low-dose infusion of oxytocin is started at 1 milli IU/min and increased by 1-2 milli IU/min every 20-30 minutes until adequate uterine contraction is obtained (Norwitz, 2003).

The second method, or active management of labor, involves a protocol of clinical management that aims to optimize uterine contractions and shorten labor. This protocol includes strict criteria for admission to the labor and delivery unit, early amniotomy, hourly cervical examinations, early diagnosis of inefficient uterine activity (if the cervical dilation rate is <1.0 cm/h), and high-dose oxytocin infusion if uterine activity is inefficient. Oxytocin infusion starts at 4 milli IU/min (or even 6 milli IU/min) and increases by 4 milli IU/min (or 6 milli IU/min) every 15 minutes until a rate of 7 contractions per 15 minutes is achieved or until the maximum infusion rate of 36 milli IU/min is reached (O'Driscoll, 1986; Norwitz, 2003).

Although active management of labor was originally intended to shorten labor in nulliparous women, its application at the National Maternity Hospital in Dublin produced a primary cesarean delivery rate of 5-6% in nulliparas (O'Driscoll, 1984). Data from randomized controlled trials confirmed that active management of labor shortens the first stage of labor and reduces the rate of maternal fever, but it does not consistently decrease the rate of cesarean delivery (Lopez-Zeno, 1992; Frigoletto, 1995; Sadler, 2000).

Although the active management protocol likely leads to early diagnosis and interventions for labor dystocia, a number of risk factors are associated with a failure of labor to progress during the first stage. These risk factors include premature rupture of the membranes (PROM), nulliparity, induction of labor, older maternal age, and complications (eg, previous perinatal death, diabetes, hypertension, infertility treatment) (Sheiner, 2002 and 2002).

A 2-hour rule has traditionally been applied for the diagnosis of labor arrest in active labor. Traditional criteria to diagnose active-phase arrest are cervical dilatation of at least 4 cm, cervical changes of <1 cm in 2 hours, and a uterine contraction pattern of >200 Montevideo units. These findings are also a common indication for cesarean delivery.

Proceeding to cesarean delivery in this setting was challenged in a clinical trial of 542 women with active-phase arrest (Rouse 1999 and 2001). Oxytocin was started, and cesarean delivery was not performed for labor arrest until adequate uterine contraction lasted at least 4 hours (>200 Montevideo units) or until oxytocin augmentation was given for 6 hours or if this contraction pattern could not be achieved. This protocol achieved vaginal delivery rates of 56-61% in nulliparas and 88% in multiparas without severe adverse maternal or neonatal outcomes. Therefore, extending the criteria for active-phase labor arrest from 2 to at least 4 hours appears to be effective in achieving vaginal birth (Rouse, 1999; ACOG, 2003).

Second stage of labor

When the woman enters the second stage of labor with complete cervical dilatation, the fetal heart rate should be monitored or auscultated at least every 5 minutes and after each contractions during the second stage (ACOG, 2005). Although the parturient may be encouraged to actively push in concordance with the contractions during the second stage, many women with epidural anesthesia who do not feel the urge to push may allow the fetus to descend passively, with a period of rest before active pushing begins.

A number of randomized controlled trials have shown that, in nulliparous women, delayed pushing is not associated with adverse perinatal outcomes or an increased risk for surgical deliveries despite an often prolonged second stage of labor (Fraser, 2000; Fitzpatrick, 2002; Hanssen, 2002). Furthermore, investigators who recently compared obstetric outcomes associated with coached versus uncoached pushing during the second stage reported a slightly shortened second stage (13 min) in the coached group, with no differences in the immediate maternal or neonatal outcomes (Bloom, 2006).

When the second stage is prolonged, clinical assessment of the women, the fetus, and the expulsive forces is warranted. Although the 2003 ACOG practice guidelines state that the duration of the second stage alone does not mandate intervention by surgical delivery if progress is being made, the clinician has several management options (continuing observation, surgical vaginal delivery, or cesarean delivery) when second-stage arrest is diagnosed.

Prolonged second stage of labor is not associated with adverse neonatal outcomes in nulliparas, possibly because of close fetal surveillance during labor, but it is associated with maternal morbidities, such as increased rates of operative vaginal and cesarean deliveries, postpartum hemorrhage, third- and fourth-degree perineal lacerations, and peripartum infection (Menticoglou, 1995, Janni, 2002; Cheng, 2003; Myles, 2003). Therefore, it is crucial to weigh the risks of surgical delivery against the potential benefits. The question of when to intervene should involve a thorough evaluation of the ongoing risks of further expectant management versus the risks of intervention with vaginal or cesarean delivery, as well as the patients' preferences.

Delivery of the fetus

When delivery is imminent, the mother is usually positioned supine with her knees bent (ie, dorsal lithotomy position), though delivery can occur with the mother in any position, including the lateral (Sims) position, the partial sitting or squatting position, or on her hands and knees (Norwitz, 2003). Although an episiotomy (an incision continuous with the vaginal introitus) used to be routinely preformed at this time, the ACOG recommended in 2006 that its use be restricted to maternal or fetal indications.

Crowning is the word used to describe when the fetal head forcibly extends the vaginal outlet. A modified Ritgen maneuver can be performed to deliver the head. Draped with a sterile towel, the heel of the clinician's hand is placed over the posterior perineum overlying the fetal chin, and pressure is applied upward to extend the fetus' head. The other hand is placed over the fetus' occiput, with pressure applied downward to flex its head. Thus, the head is held in mid position until it is delivered, followed by suctioning of the oropharynx and nares. Check the fetus' neck for a wrapped umbilical cord, and promptly reduce it if possible. If the cord is wrapped too tightly to be removed, the cord can be double clamped and cut.

Next, the fetus' anterior shoulder is delivered with gentle downward traction on its head and chin. Subsequent upward pressure in the opposite direction facilitates delivery of the posterior shoulder. The rest of the fetus should now be easily delivered with gentle traction away from the mother. If not done previously, the cord is clamped and cut. The baby is vigorously stimulated and dried and then transferred to the care of the waiting attendants or placed on the mother's abdomen.

Third stage of labor - Delivery of the placenta and the fetal membranes

The labor process has now entered the third stage, ie, delivery of the placenta. Three classic signs indicate that the placenta has separated from the uterus: (1) The uterus contracts and rises, (2) the cord suddenly lengthens, and (3) a gush of blood occurs (Norwitz, 2003).

Delivery of the placenta usually happens within 5-10 minutes after delivery of the fetus, but it is considered normal up to 30 minutes after delivery. Excessive traction should not be applied to the cord to avoid inverting the uterus, which is an obstetric emergency. The placenta can also be manually separated by passing a hand between the placenta and uterine wall. After the placenta is delivered, inspect it for completeness and for the presence of 1 umbilical vein and 2 umbilical arteries. Oxytocin can be administered throughout the third stage to facilitate placental separation by inducing uterine contractions and to decrease bleeding.

Expectant management of the third stage involves allowing the placenta to deliver spontaneously, whereas active management involves administration of uterotonic agent (usually oxytocin, an ergot alkaloid, or prostaglandins) before the placenta is delivered. This is done with early clamping and cutting of the cord and with controlled traction on the cord while placental separation and delivery are awaited.

A review of 5 randomized trials to compare active versus expectant management of the third stage demonstrated that active management was associated with lowered risks of maternal blood loss, postpartum hemorrhage, and prolongation of the third stage, but it increased maternal nausea, vomiting, and blood pressure (when ergometrine was used) (Prendiville, 2000). A multicenter randomized controlled trial of the efficacy of misoprostol (prostaglandin E1 analog) compared with oxytocin showed that oxytocin 10 IU IV or given intramuscularly (IM) was preferable to oral misoprostol 600 mcg for active management of the third stage of labor in hospital settings (Gulmezoglu, 2001). Therefore, if the risks and benefits are balanced, active management with oxytocin may be considered a part of routine management of the third stage.

After the placenta is delivered, the labor and delivery period is complete. Palpate the patient's abdomen to confirm reduction in the size of the uterus and its firmness. Ongoing blood loss and a boggy uterus suggest uterine atony. Thoroughly examine the birth canal, including the cervix and the vagina, the perineum, and the distal rectum. Repair episiotomies or lacerations.

PAIN CONTROL

Section 8 of 9  

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

Uterine contractions result in visceral pain, which is innervated by T10-L1. While in descent, the fetus' head exerts pressure on the mother's pelvic floor, vagina, and perineum, causing somatic pain transmitted by the pudendal nerve (innervated by S2-4) (ACOG, 2002). Therefore, optimal pain control during labor should relieve both sources of pain.

A number of opioid agonists and opioid agonist-antagonists can be given in intermittent doses for systemic pain control. These include meperidine 25-50 mg IV every 1-2 hours or 50-100 mg IM every 2-4 hours, fentanyl 50-100 mcg IV every hour, nalbuphine 10 mg IV or IM every 3 hours, butorphanol 1-2 mg IV or IM every 4 hours, and morphine 2-5 mg IV or 10 mg IM every 4 hours (ACOG, 2002). As an alternative, regional anesthesia may be given. Options are epidural, spinal, and combined spinal epidural anesthesia. These provide partial to complete blockage of pain sensation below T8-10, with various degree of motor blockade. These blocks can be used during labor and for surgical deliveries.

Studies performed to compare the analgesic effect of regional anesthesia and parenteral agents showed that regional anesthesia provides superior pain relief (Ramin, 1995; Bofil, 1997; Sharma, 1997). Although some researchers reported that epidural anesthesia is associated with a slight increase in the duration of labor and in the rate of surgical vaginal delivery (Alexander, 2002; Halpern, 2004), large randomized controlled studies did not reveal a difference in rates of cesarean delivery between women who received parenteral analgesics compared with women who received epidural anesthesia (Ramin, 1995; Sharma, 1997; Halpern, 2004) given during early-stage or late labor (Wong, 2005). Although regional anesthesia is effective as a method of pain control, common adverse effects include maternal hypotension, maternal temperature >100.4°F, postdural puncture headache, transient fetal heart deceleration, and pruritus (with added opioids) (ACOG, 2002).

Despite the many methods available for analgesia and anesthesia to manage labor pain, some women may not wish to use conventional pain medications during labor, opting instead for natural childbirth. Although these women may use breathing and mental exercises to help alleviate labor pain, they should be assured that pain relief can be administered at any time during labor.

Of note, use of nonsteroidal anti-inflammatory drugs (NSAIDs) are relatively contraindicated in the third trimester of pregnancy. The repeated use of NSAIDs has been associated with early closure of the fetal ductus arteriosus in utero and with decreasing fetal renal function leading to oligohydramnios.

REFERENCES

Section 9 of 9

• Authors and Editors
• Definition
• Stages of Labor and Epidemiology
• Mechanism of Labor, or Cardinal Movements
• Clinical History and Physical Examination
• Workup
• Intrapartum Management of Labor
• Pain Control
• References

• ACOG. American College of Obstetricians and Gynecologists Practice Bulletin. Dystocia and augmentation of labor. Clinical management guidelines for obstetricians-gynecologists. No 49. Washington, DC: American College of Obstetricians and Gynecologists;. December 2003.
• ACOG. American College of Obstetricians and Gynecologists Practice Bulletin. Intrapartum Fetal Heart Rate Monitoring. Clinical Management Guidelines for Obstetricians-Gynecologists. No 36. Washington, DC: American College of Obstetricians and Gynecologists;. December 2005.
• ACOG. American College of Obstetricians and Gynecologists Practice Bulletin. Episiotomy. Clinical Management Guidelines for Obstetricians-Gynecologists. No 71. Washington, DC: American College of Obstetricians and Gynecologists;. April 2006.
• ACOG. American College of Obstetricians and Gynecologists Practice Bulletin. Obstetric Analgesia and Anesthesia. Clinical Management Guidelines for Obstetricians-Gynecologists. No 36. Washington, DC: American College of Obstetricians and Gynecologists;. July 2002.
• Albers LL, Schiff M, Gorwoda JG. The length of active labor in normal pregnancies. Obstet Gynecol. Mar 1996;87(3):355-9. [Medline].
• Alexander JM, Sharma SK, McIntire DD. Epidural analgesia lengthens the Friedman active phase of labor. Obstet Gynecol. Jul 2002;100(1):46-50.
• Beckmann CR, Ling FW, Barzansky BM. Obstetrics and Gynecology. 2nd ed. Philadelphia, Pa: Lippincott Williams & Wilkins;. 1992:169-83.
• Bloom SL, McIntire DD, Kelly MA, et al. Lack of effect of walking on labor and delivery. N Engl J Med. Jul 9 1998;339(2):76-9.
• Bloom SL, Casey BM, Schaffer JI, et al. A randomized trial of coached versus uncoached maternal pushing during the second stage of labor. Am J Obstet Gynecol. Jan 2006;194(1):10-3.
• Bofill JA, Vincent RD, Ross EL, et al. Nulliparous active labor, epidural analgesia, and cesarean delivery for dystocia. Am J Obstet Gynecol. Dec 1997;177(6):1465-70.
• Caldwell WE, Moloy HC. Anatomical variations in the female pelvis and their effect in labor with a suggested classification. Am J Obstet Gynecol. 1933;26:479.
• Cheng YW, Hopkins LM, Caughey AB. How long is too long: Does a prolonged second stage of labor in nulliparous women affect maternal and neonatal outcomes?. Am J Obstet Gynecol. Sep 2004;191(3):933-8.
• Creasy RK, Resnik R. Maternal-Fetal Medicine: Principles and Practice. 3rd ed. Philadelphia, Pa: WB Saunders;. 1993.
• Cunningham FG, Gant NF, Leveno KJ. Williams Obstetrics. 21st ed. New York, NY: McGraw-Hill;. 2002: 249-420.
• Duignan NM, Studd JW, Hughes AO. Characteristics of normal labour in different racial groups. Br J Obstet Gynaecol. Aug 1975;82(8):593-601.
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Article Last Updated: Jul 12, 2006