Normal Labor and Delivery

Labor is a physiologic process during which the fetus, membranes, umbilical cord, and placenta are expelled from the uterus.

Stages of labor

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

First stage of labor

• Begins with regular uterine contractions and ends with complete cervical dilatation at 10 cm

• Divided into a latent phase and an active phase

• The latent phase begins with mild, irregular uterine contractions that soften and shorten the cervix

• Contractions become progressively more rhythmic and stronger

• The active phase usually begins at about 3-4 cm of cervical dilation and is characterized by rapid cervical dilation and descent of the presenting fetal part

Second stage of labor

• Begins with complete cervical dilatation and ends with the delivery of the fetus

• In nulliparous persons, the second stage should be considered prolonged if it exceeds 3 hours if regional anesthesia is administered or 2 hours in the absence of regional anesthesia

• In multiparous persons, the second stage should be considered prolonged if it exceeds 2 hours with regional anesthesia or 1 hour without it ^[1]

Third stage of labor

• The period between the delivery of the fetus and the delivery of the placenta and fetal membranes

• Delivery of the placenta often takes less than 10 minutes, but the third stage may last as long as 30 minutes

• Expectant management involves spontaneous delivery of the placenta

• The third stage of labor is considered prolonged after 30 minutes, and active intervention is commonly considered ^[2]

• Active management often involves prophylactic administration of oxytocin or other uterotonics (prostaglandins or ergot alkaloids), cord clamping/cutting, and controlled traction of the umbilical cord

Mechanism of labor

The mechanisms of labor, also known as the cardinal movements, involve changes in the position of the fetus’s head during its passage in labor. These are described in relation to a vertex presentation. Although labor and delivery occurs in a continuous fashion, the cardinal movements are described as the following 7 discrete sequences ^[2] :

1. Engagement

2. Descent

3. Flexion

4. Internal rotation

5. Extension

6. Restitution and external rotation

7. Expulsion

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 elicit the following information:

• Frequency and time of onset of contractions

• 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)

• Fetal movements

• Presence or absence of vaginal bleeding.

Braxton-Hicks contractions must be differentiated from true contractions. Typical features of Braxton-Hicks contractions are as follows:

• Usually occur no more often than once or twice per hour, and often just a few times per day

• Irregular and do not increase in frequency with increasing intensity

• Resolve with ambulation or a change in activity

Contractions that lead to labor have the following characteristics:

• May start as infrequently as every 10-15 minutes, but usually accelerate over time, increasing to contractions that occur every 2-3 minutes

• Tend to last longer and are more intense than Braxton-Hicks contractions

• Lead to cervical change

Physical examination

The physical examination should include documentation of the following:

• Maternal vital signs

• Fetal presentation

• Assessment of fetal well-being

• Frequency, duration, and intensity of uterine contractions

• Abdominal examination with Leopold maneuvers

• Pelvic examination with sterile gloves

Digital examination allows the clinician to determine the following aspects of the cervix:

• Degree of dilatation, which ranges from 0 cm (closed or fingertip) to 10 cm (complete or fully dilated)

• Effacement (assessment of the cervical length, which can be reported as a percentage of the normal 3- to 4-cm–long cervix or described as the actual cervical length)

• Position (ie, anterior or posterior)

• 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. ^[2]

Intrapartum management of labor

First stage of labor

On admission to the labor and delivery suite, persons having normal labor should be encouraged to assume the position that they find most comfortable. Possibilities including the following:

• Walking

• Lying supine

• Sitting

• Resting in a left lateral decubitus position

Management includes the following:

• Periodic assessment of the frequency and strength of uterine contractions and changes in cervix and in the fetus' station and position

• Monitoring the fetal heart rate at least every 15 minutes, particularly during and immediately after uterine contractions; in most obstetric units, the fetal heart rate is assessed continuously ^[3]

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 contraction. ^[3] Prolonged duration of the second stage alone does not mandate operative delivery if progress is being made, but management options for second-stage arrest include the following:

• Continuing observation/expectant management

• Operative vaginal delivery by forceps or vacuum-assisted vaginal delivery, or cesarean delivery.

Delivery of the fetus

Positioning of the patient for delivery can be any of the following ^[2] :

• Supine with the knees bent (ie, dorsal lithotomy position; the usual choice)

• Lateral (Sims) position

• Partial sitting or squatting position

• On the hands and knees

Episiotomy used to be routinely performed at this time, but current recommendations restrict its use to maternal or fetal indications

Delivery maneuvers are as follows:

• The head is held in mid position until it is delivered, followed by suctioning of the oropharynx and nares

• Check the fetus's 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

• The fetus's 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 birthing parent

• 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 birthing parent's abdomen

Third stage of labor

The following 3 classic signs indicate that the placenta has separated from the uterus ^[2] :

• The uterus contracts and rises

• The umbilical cord suddenly lengthens

• A gush of blood occurs

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 of the fetus.

Pain control

Agents given in intermittent doses for systemic pain control include the following ^[4] :

• 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

• Morphine, 2-5 mg IV or 10 mg IM every 4 hours

As an alternative, regional anesthesia may be given. Anesthesia options include the following:

• Epidural

• Spinal

• Combined spinal-epidural

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. ^{[1, 2]}

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 insufficiency, whereas uterine contraction without cervical change does not meet the definition of labor.

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 10 cm. In Friedman’s landmark studies of 500 nulliparas, ^[5]  he subdivided the first stage into an early latent phase and an ensuing active phase. The latent phase begins with mild, irregular uterine contractions that soften and shorten the cervix. The contractions become progressively more rhythmic and stronger. This is followed by the active phase of labor, which usually begins at about 3-4 cm of cervical dilation and is characterized by rapid cervical dilation and descent of the presenting fetal part. The first stage of labor ends with complete cervical dilation at 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 labor curve, and a series of definitions of labor protraction and arrest were subsequently established. ^{[6, 7]} However, subsequent data of modern obstetric population suggest that the rate of cervical dilatation is slower and the progression of labor may be significantly different from that suggested by the Friedman labor curve. ^{[8, 9, 10]}

Second stage of labor

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

Studies performed to examine perinatal outcomes associated with a prolonged second stage of labor revealed increased risks of operative deliveries and maternal morbidities but no differences in neonatal outcomes. ^{[11, 12, 13, 14]} Maternal risk factors associated with a prolonged second stage include nulliparity, increasing maternal weight and/or weight gain, use of regional anesthesia, induction of labor, fetal occiput in a posterior or transverse position, and increased birthweight. ^{[13, 14, 15, 16]}

Third stage of labor

The third stage of labor is defined by the time period between the delivery of the fetus and the delivery of the placenta and fetal membranes. During this period, uterine contraction decreases basal blood flow, which results in thickening and reduction in the surface area of the myometrium underlying the placenta with subsequent detachment of the placenta. ^[17] Although delivery of the placenta often requires less than 10 minutes, the duration of the third stage of labor may last as long as 30 minutes.

Expectant management of the third stage of labor involves spontaneous delivery of the placenta. Active management often involves prophylactic administration of oxytocin or other uterotonics (prostaglandins or ergot alkaloids), cord clamping/cutting, and controlled cord traction of the umbilical cord. Andersson et al found that delayed cord clamping (≥180 seconds after delivery) improved iron status and reduced prevalence of iron deficiency at age 4 months and also reduced prevalence of neonatal anemia, without apparent adverse effects. ^[18]

A systematic review of the literature that included 5 randomized controlled trials comparing active and expectant management of the third stage reports that active management shortens the duration of the third stage and is superior to expectant management with respect to blood loss/risk of postpartum hemorrhage; however, active management is associated with an increased risk of unpleasant side effects. ^[19]

The third stage of labor is considered prolonged after 30 minutes, and active intervention, such as manual extraction of the placenta, is commonly considered. ^[2]

Epidemiology

As the childbearing population in the United States has changed, the clinical obstetric management of labor also has evolved since Friedman's studies. Data from number a studies have suggested that normal labor can progress at a rate much slower than that Friedman and Sachtleben ^{[6, 7]} had described. Zhang et al 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. ^[20] Kilpatrick et al ^[8] and Albers et al ^[9] also reported that the median lengths of first and second stages of labor were longer than those Friedman suggested.

A number of investigators have identified several maternal characteristics obstetric factors that are associated with the length of labor. One group reported that increasing maternal age was associated with a prolonged second stage but not first stage of labor. ^[21]

While nulliparity is associated with a longer labor compared to multiparas, increasing parity does not further shorten the duration of labor. ^[22] Some authors have observed that the length of labor differs among racial/ethnic groups. One group reported that Asian women have the longest first and second stages of labor compared with Caucasian or African American women ^[23] , and American Indian women had second stages shorter than those of non-Hispanic Caucasian women. ^[9] However, others report conflicting findings. ^{[24, 25]} Differences in the results may have been due to variations in study designs, study populations, labor management, or statistical power.

In one large retrospective study of the length of labor, specifically with respect to race and/or ethnicity, the authors observed no significant differences in the length of the first stage of labor among different racial/ethnic groups. 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. ^[26]

According to a systematic review of 13 trials involving 16,242 women, most women whose prenatal and childbirth care were led by a midwife had better outcomes compared with those whose care was led by a physician or shared among disciplines. Patients who received midwife-led pregnancy care were less likely to have regional analgesia, episiotomy, and instrumental birth and more likely to have no intrapartum analgesia or anesthesia, spontaneous vaginal birth, attendance at birth by a known midwife, and a longer mean length of labor. They were also less likely to have preterm birth and fetal loss before 24 weeks' gestation. However, the average risk ratio for caesarean births did not differ between groups, and there were no differences in fetal loss/neonatal death at 24 or more weeks' gestation or in overall fetal/neonatal death. ^{[1, 27]}

Concerns associated with midwife-attended home births

However, concerns about the effect of midwife-attended home births on neonatal health were raised by an analysis of nearly 14 million singleton, full-term births, from 2007-2010, of infants of normal weight. The data, from the National Center for Health Statistics, indicated that delivering at home was associated with a greater than 10-fold increased risk for an Apgar score of 0 and a nearly 4-fold increased risk for neonatal seizure or serious neurologic dysfunction, as compared with hospital delivery. ^{[28, 29]}

Compared with delivery by a hospital physician, midwife-attended home birth was associated with a relative risk (RR) of 10.55 for an Apgar score of 0. For midwife deliveries at freestanding birth centers, the RR was 3.56, and for hospital midwife deliveries, the RR was 0.55. ^{[28, 29]}

In the same study, the RR for neonatal seizures or serious neurologic disorders for midwife-attended home births, compared with physician-attended hospital delivery, was 3.80. Compared with in-hospital physician delivery, the RR for midwife delivery at freestanding birth centers was 1.88, and for hospital midwife delivery, the RR was 0.74. ^{[28, 29]}

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. ^[2]

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.

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 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, contractions that lead to labor tend to last longer and are more intense, leading to cervical change. True labor is defined as uterine contractions leading to cervical changes. If contractions occur without cervical changes, it is not 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 usually accelerate over time, increasing to contractions that occur 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 patient may feel that the baby has become light. As the presenting fetal part starts to drop, the shape of the patient's abdomen may change to reflect descent of the fetus. Breathing may be relieved because tension on the diaphragm is reduced, whereas urination may become more frequent due to the added pressure on the urinary bladder.

Physical examination

Physical examination should include documentation of the patient's vital signs, the fetus' presentation, and assessment of the fetal well-being. The frequency, duration, and intensity of uterine contractions should be assessed, particularly the abdominal and pelvic examinations in patients who present in possible labor.

Abdominal examination begins with the Leopold maneuvers described below ^[2] :

• 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 patient's pelvis. The examiner stands facing the patient'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 often performed using sterile gloves to decrease the risk of infection. 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 can be reported as a percentage of the normal 3- to 4-cm-long cervix or described as the actual cervical length); actual reporting of cervical length may decrease potential ambiguity in percent-effacement reporting, (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). ^[2]

The pelvis can also be assessed either by clinical examination (clinical pelvimetry) or radiographically (CT or MRI). The pelvic planes include the following:

• Pelvic inlet: The obstetrical conjugate is the distance between the sacral promontory and the inner pubic arch; it should measure 11.5 cm or more. The diagonal conjugate is the distance from the undersurface of the pubic arch to sacral promontory; it is 2 cm longer than the obstetrical conjugate. The transverse diameter of the pelvic inlet measures 13.5 cm.

• Midpelvis: The midpelvis is the distance between the bony points of ischial spines, and it typically exceeds 12 cm.

• Pelvic outlet: The pelvic outlet is the distance between the ischial tuberosities and the pubic arch. It usually exceeds 10 cm.

The shape of the patient's pelvis can also be assessed and classified into 4 broad categories based on the descriptions of Caldwell and Moloy: gynecoid, anthropoid, android, and platypelloid. ^[30] Although the gynecoid and anthropoid pelvic shapes are thought to be most favorable for vaginal delivery, many patients can be classified into 1 or more pelvic types, and such distinctions can be arbitrary. ^[2]

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. ^[31] Therefore, all pregnancies require a thorough evaluation of risks and close surveillance. As soon as the patient 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.

In the presence of labor progression, monitoring of uterine contractions by external tocodynamometry is often adequate. However, if a laboring person is confirmed to have rupture of the membranes and if the intensity/duration of the contractions cannot be adequately assessed, an intrauterine pressure catheter can be inserted into the uterine cavity past the fetus to determine the onset, duration, and intensity of the contractions. Because the external tocometer records only the timing of contractions, an intrauterine pressure catheter can be used to measure the intrauterine pressure generated during uterine contractions if their strength is a concern. While it is considered safe, placental abruption has been reported as a rare complication of an intrauterine pressure catheter placed extramembraneously. ^{[32, 33]}

Bedside ultrasonography may be used to assess the risk of gastric content aspiration in pregnant persons during labor, by measuring the antral cross-sectional area (CSA), according to a study by Bataille et al. ^{[34, 35]} In the report, which involved 60 women in labor who were under epidural analgesia, the investigators found that at epidural insertion, half of the women had an antral CSA of over 320 mm², indicating that they were at increased risk of gastric content aspiration while under anesthesia. ^{[34, 35]}

It was also found that the antral CSA was reduced during labor, falling from a median of 319 mm² at epidural insertion to 203 mm² at full cervical dilatation, with only 13% of the women at that time still considered at risk of aspiration. ^{[34, 35]} This change, according to the investigators, suggested that even under epidural anesthesia, gastric motility is preserved.

Often, fetal monitoring is achieved using cardiotography, or electronic fetal monitoring. Cardiotography as a form of fetal assessment in labor was reviewed using randomized and quasirandomized controlled trials involving a comparison of continuous cardiotocography with no monitoring, intermittent auscultation, or intermittent cardiotocography. This review concluded that continuous cardiotocography during labor is associated with a reduction in neonatal seizures but not cerebral palsy or infant mortality; however, continuous monitoring is associated with increased cesarean and operative vaginal deliveries. ^[36]

If nonreassuring fetal heart rate tracings by cardiotography (eg, late decelerations) are noted, a fetal scalp electrode may be applied to generate sensitive readings of beat-to-beat variability. However, a fetal scalp electrode should be avoided if the birthing parent has HIV, hepatitis B or hepatitis C infections, or if fetal thrombocytopenia is suspected. A framework has been suggested to classify and standardize the interpretation of a fetal heart rate monitoring pattern according to the risk of fetal acidemia with the intention of minimizing neonatal acidemia without excessive obstetric intervention. ^[37]

The question of whether fetal pulse oximetry may be useful for fetal surveillance in labor was examined in a review of 5 published trials comparing fetal pulse oximetry and cardiotography with cardiotography alone. It concluded that existing data provide limited support for the use of fetal pulse oximetry when used in the presence of a nonreassuring fetal heart rate tracing to reduce caesarean delivery for nonreassuring fetal status. The addition of fetal pulse oximetry does not reduce overall caesarean deliveries. ^[38]

Further evaluation of a fetus at risk for labor intolerance or distress 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 of the parturient, such as complete blood cell (CBC) count, blood typing and screening, and urinalysis, are usually performed. Intravenous (IV) access is established.

First stage of labor

Cervical change occurs at a slow, gradual pace during the latent phase of the first stage of labor. Latent phase of labor is complex and not well-studied since determination of onset is subjective and may be challenging as women present for assessment at different time duration and cervical dilation during labor. In a cohort of women undergoing induction of labor, the median duration of latent labor was 384 min with an interquartile range of 240-604 min. The authors report that cervical status at admission for labor induction, but not other risk factors typically associated with cesarean delivery, is associated with length of the latent phase. ^[39]

Most patients experience onset of labor without premature rupture of the membranes (PROM); however, approximately 8% of term pregnancies is complicated by PROM. Spontaneous onset of labor usually follows PROM such that 50% of women with PROM who were expectantly managed delivered within 5 hours, and 95% gave birth within 28 hours of PROM. ^[40]  The American College of Obstetricians and Gynecologists (ACOG) recommends that fetal heart rate monitoring should be used to assess fetal status and dating criteria reviewed, and group B streptococcal prophylaxis be given based on prior culture results or risk factors of cultures not available. Additionally, randomized controlled trials to date suggest that for women with PROM at term, labor induction, usually with oxytocin infusion, at time of presentation can reduce the risk of chorioamnionitis. ^[41]

According to Friedman and colleagues, ^[6] 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. Particularly, obstetric interventions such as induction of labor, augmentation of labor with oxytocin administration, use of regional anesthesia for pain control, and continuous fetal heart rate monitoring are increasingly common practice in the management of labor in today’s obstetric population. ^{[42, 43, 20]} Vaginal breech and mid- or high-forceps deliveries are now rarely performed. ^{[44, 45, 46]} Therefore, subsequent authors have suggested normal labor may precede at a rate less rapid than those previously described. ^{[8, 9, 20]}

Data collected from the Consortium on Safe Labor suggests that allowing labor to continue longer before 6-cm dilation may reduce the rate of intrapartum and subsequent cesarean deliveries in the United States. ^[47] In the study, the authors noted that the 95^th percentile for advancing from 4-cm dilation to 5-cm dilation was longer than 6 hours; and the 95^th percentile for advancing from 5-cm dilation to 6-cm dilation was longer than 3 hours, regardless of the patient’s parity.

On admission to the labor and delivery suite, a person having normal labor should be encouraged to assume the position that is 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. ^[48]

The patient and family or support team should be consulted regarding the risks and benefits of various interventions, such as the augmentation of labor using oxytocin, artificial rupture of the membranes, methods and pharmacologic agents for pain control, and operative vaginal delivery (including forceps or vacuum-assisted vaginal deliveries) or cesarean delivery. They should be actively involved, and their preferences should be considered in the management decisions made during labor and delivery. ^[2]

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 performed only when necessary to minimize the risk of chorioamnionitis, particularly in patients 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. ^[3]

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 mili IU/min and increased by 1-2 mili IU/min every 20-30 minutes until adequate uterine contraction is obtained. ^[2]

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 mili IU/min (or even 6 mili IU/min) and increases by 4 mili IU/min (or 6 mili IU/min) every 15 minutes until a rate of 7 contractions per 15 minutes is achieved or until the maximum infusion rate of 36 mili IU/min is reached. ^{[49, 2]}

ACOG recommends amniotomy for patients undergoing augmentation or induction of labor to shorten the duration of labor. Additionally, either low- or high-dose oxytocin administration can be used for the active management of labor to reduce operative deliveries. ^[50]

Although active management of labor was originally intended to shorten the length of labor in nulliparous women, its application at the National Maternity Hospital in Dublin produced a primary cesarean delivery rate of 5-6% in nulliparas. ^[51] Data from randomized controlled trials confirmed that active management of labor shortens the first stage of labor and reduces the likelihood of maternal febrile morbidity, but it does not consistently decrease the probability of cesarean delivery. ^{[52, 53, 54]}

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, increasing maternal age, and or other complications (eg, previous perinatal death, pregestational or gestational diabetes mellitus, hypertension, infertility treatment). ^{[55, 56]}

While the ACOG defines labor dystocia as abnormal labor that results form abnormalities of the power (uterine contractions or maternal expulsive forces), the passenger (position, size, or presentation of the fetus), or the passage (pelvis or soft tissues), labor dystocia can rarely be diagnosed with certainty. ^{[1, 50]} Often, a "failure to progress" in the first stage is diagnosed if uterine contraction pattern exceeds 200 Montevideo units for 2 hours without cervical change during the active phase of labor is encountered. ^[1] Thus, the 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, or the "2-hour rule," was challenged in a clinical trial of 542 women with active phase arrest. ^[57] In this cohort of women diagnosed with active phase arrest, 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 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. ^{[57, 1]}

Second stage of labor

When the patient 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 contraction during the second stage. ^[3] Although the parturient may be encouraged to actively push in concordance with the contractions during the second stage, many persons 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, or passive descend, is not associated with adverse perinatal outcomes or an increased risk for operative deliveries despite an often prolonged second stage of labor. ^{[58, 59, 40]} Furthermore, investigators who 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. ^[60]

Le Ray et al reported that manual rotation of fetuses who were in occiput posterior or occiput transverse position at full dilatation was associated with reduced rates of operative delivery (ie, cesarean or instrumental vaginal delivery). ^{[61, 62]} In a study involving 2 French hospitals, operative delivery rates were significantly lower at the institution whose policy favored manual rotation than at the one that favored modification of maternal position (23.2% vs 38.7%), mainly because of lower rates of instrumental deliveries (15.0% vs 28.8%).

When a prolonged second stage of labor is encountered, clinical assessment of the parturient, the fetus, and the expulsive forces is warranted. A randomized controlled trial performed by Api et al determined that application of fundal pressure on the uterus does not shorten the second stage of labor. ^[63] Although the 2003 ACOG practice guidelines state that the duration of the second stage alone does not mandate intervention by operative vaginal delivery or cesarean delivery if progress is being made, the clinician has several management options (continuing observation/expectant management, operative vaginal delivery by forceps or vacuum-assisted vaginal delivery, or cesarean delivery) when second-stage arrest is diagnosed.

The association between a prolonged second stage of labor and adverse maternal or neonatal outcome has been examined. While a prolonged second stage is not associated with adverse neonatal outcomes in nulliparas, possibly because of close fetal surveillance during labor, but it is associated with increased maternal morbidity, including higher likelihood of operative vaginal delivery and cesarean delivery, postpartum hemorrhage, third- or fourth-degree perineal lacerations, and peripartum infection. ^{[11, 12, 13, 14]} Therefore, it is crucial to weigh the risks of operative delivery against the potential benefits of continuing labor in hopes to achieve vaginal delivery. 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 patient is usually positioned supine with her knees bent (ie, dorsal lithotomy position), though delivery can occur with the patient in any position, including the lateral (Sims) position, the partial sitting or squatting position, or on her hands and knees. ^[2] Although an episiotomy (an incision continuous with the vaginal introitus) used to be routinely performed at this time, the ACOG recommended in 2006 that its use be restricted to maternal or fetal indications. Studies have also shown that routine episiotomy does not decrease the risk of severe perineal lacerations during forceps or vacuum-assisted vaginal deliveries. ^{[64, 65]}

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. Of note, some providers, in an attempt to avoid shoulder dystocia, deliver the anterior shoulder prior to restitution of the fetal head.

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 birthing parent. 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 birthing parent'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. ^[2]

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 of the fetus. Excessive traction should not be applied to the cord to avoid inverting the uterus, which can cause severe postpartum hemorrhage and 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 comparing 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). However, given the reduced risk of complications, this review recommends that active management is superior to expectant management and should be the routine management of choice. ^[19]

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. ^[66] Therefore, if the risks and benefits are balanced, active management with oxytocin may be considered a part of routine management of the third stage. A study by Adnan et al that included 1075 women to compare intravenous oxytocin and intramuscular oxytocin for the third stage of labor reported that although intravenous oxytocin did not lower the incidence of standard postpartum hemorrhage, it significantly lowered the incidence of severe postpartum hemorrhage as well as lowering the frequency of blood transfusion and admission to a high dependency unit. ^[67]

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. A thorough examination of the birth canal, including the cervix and the vagina, the perineum, and the distal rectum, is warranted, and repair of episiotomy or perineal/vaginal lacerations should be carried out.

Franchi et al found that topically applied lidocaine-prilocaine (EMLA) cream was an effective and satisfactory alternative to mepivacaine infiltration for pain relief during perineal repair. In a randomized trial of 61 women with either an episiotomy or a perineal laceration after vaginal delivery, women in the EMLA group had lower pain scores than those in the mepivacaine group (1.7 +/- 2.4 vs 3.9 +/- 2.4; P = .0002), and a significantly higher proportion of women expressed satisfaction with anesthesia method in the EMLA group than in the mepivacaine group (83.8% vs 53.3%; P = .01). ^[68]

In a Cochrane review, Aasheim et al suggest that evidence is sufficient to support the use of warm compresses to prevent perineal tears. They also found a reduction in third-degree and fourth-degree tears with massage of the perineum to reduce the rate of episiotomy. ^[69]

The World Health Organization developed a checklist to address the major causes of maternal death (hemorrhage, infection, obstructed labor and hypertensive disorders), intrapartum-related stillbirths (inadequate intrapartum care), and neonatal deaths (birth asphyxia, infection and complications related to prematurity). ^{[70, 71]}

Laboring patients often experience intense pain. Uterine contractions result in visceral pain, which is innervated by T10-L1. While in descent, the fetus' head exerts pressure on the pelvic floor, vagina, and perineum, causing somatic pain transmitted by the pudendal nerve (innervated by S2-4). ^[4] 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. ^[4] As an alternative, regional anesthesia may be given. Options are epidural, spinal, or 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. ^{[72, 45, 73]} Although some researchers reported that epidural anesthesia is associated with a slight increase in the duration of labor and in the rate of operative vaginal delivery, ^{[74, 75]} large randomized controlled studies did not reveal a difference in frequency of cesarean delivery between women who received parenteral analgesics compared with women who received epidural anesthesia ^{[72, 73, 75, 76, 77]} given during early-stage or later in labor. ^[78]

Additionally, an analysis of studies published since 2005 in a Cochrane review showed epidural analgesia was not associated with an increase in the rate of assisted vaginal delivery. ^{[76, 77]} 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). ^[4]

Despite the many methods available for analgesia and anesthesia to manage labor pain, some persons may not wish to use conventional pain medications during labor, opting instead for a natural childbirth. Although these patients 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.

A Cochrane review update concluded that relaxation techniques and yoga may offer some relief and improve management of pain. Studies in the review noted increased satisfaction with pain relief and lower assisted vaginal delivery rates with relaxation techniques. One trial involving yoga noted reduced pain, increased satisfaction with pain relief, increased satisfaction with the childbirth experience, and reduced length of labor. ^[79]

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.

ACOG made the following recommendations concerning delivery of a newborn with meconium-stained amniotic fluid ^[80] :

• Infants with meconium-stained amniotic fluid should no longer routinely receive intrapartum suctioning. However, a team with full resuscitation skills that include endotracheal intubation should be available.
• The same procedures for resuscitation for infants with clear fluid should be followed for infants with meconium-stained fluid.