INVOLUTION OF THE REPRODUCTIVE TRACT
 Birth Canal
 Return to the nonpregnant state begins soon after delivery. The vagina and its outlet gradually diminish in size but rarely regain their nulliparous dimensions. Rugae begin to reappear by the third week but are less prominent than before. The hymen is represented by several small tags of tissue, which scar to form the myrtiform caruncles. Vaginal epithelium begins to proliferate by 4 to 6 weeks, usually coincidental with resumed ovarian estrogen production. Lacerations or stretching of the perineum during delivery may result in vaginal outlet relaxation. Some damage to the pelvic floor may be inevitable, and parturition predisposes to urinary incontinence and pelvic organ prolapse. This is discussed in detail in Chapter 27 (p. 536).
Uterus
 The massively increased uterine blood flow necessary to maintain pregnancy is made possible by significant hypertrophy and remodeling of pelvic vessels. After delivery, their caliber gradually diminishes to approximately that of of the prepregnant state. Within the puerperal uterus, larger blood vessels become obliterated by hyaline changes, are gradually resorbed, and are replaced by smaller ones. Minor vestiges of the larger vessels, however, may persist for years. During labor, the margin of the dilated cervix, which corresponds to the external os, may be lacerated. The cervical opening contracts slowly and for a few days immediately after labor, readily admits two fingers. By the end of the first week, this opening narrows, the cervix thickens, and the endocervical canal reforms. The external os does not completely resume its pregravid appearance. It remains somewhat wider, and typically, ectocervical depressions at the site of lacerations become permanent. These changes are characteristic of a parous cervix (Fig. 36-1). The markedly attenuated lower uterine segment contracts and retracts, but not as forcefully as the uterine corpus. During the next few weeks, the lower segment is converted from a clearly distinct substructure large enough to accommodate the fetal head to a barely discernible uterine isthmus located between the corpus and internal os. FIGURE 36-1 Common appearance of nulliparous (A) and parous (B) cervices. Cervical epithelium also undergoes considerable remodeling, and this actually may be salutary. Ahdoot and associates (1998) found that approximately half of women showed regression of high-grade dysplasia following vaginal delivery. Kaneshiro and coworkers (2005) found similar regression—about 60 percent overall—regardless of delivery mode. Postpartum, the fundus of the contracted uterus lies slightly below the umbilicus. It consists mostly of myometrium covered by serosa and internally lined by basal decidua. The anterior and posterior walls, which lie in close apposition, are each 4 to 5 cm thick (Buhimschi, 2003). At this time, the uterus weighs approximately 1000 g. Because blood vessels are compressed by the contracted myometrium, the uterus on section appears ischemic compared with the reddish-purple hyperemic pregnant organ. Myometrial involution is a truly remarkable tour de force of destruction or deconstruction that begins as soon as 2 days after delivery as shown in Figure 36-2. As emphasized by Hytten (1995), studies that describe the degree of decreasing uterine weight postpartum are poor quality. Best estimates are that by 1 week, the uterus weighs approximately 500 g; by 2 weeks, about 300 g; and at 4 weeks, involution is complete and the uterus weighs approximately 100 g. After each successive delivery, the uterus is usually slightly larger than before the most recent pregnancy. The total number of myocytes does not decrease appreciably—rather, their size decreases markedly. FIGURE 36-2 Cross sections of uteri made at the level of the involuting placental site at varying times after delivery. p.p. = postpartum. (Redrawn from Williams, 1931.) Sonographic Findings Uterine size dissipates rapidly in the first week (Fig. 36-3). And the uterus and endometrium return to pregravid size by 8 weeks after delivery (Belachew, 2012; Steinkeler, 2012). In a study of 42 normal women postpartum, Tekay and Jouppila (1993) identified fluid in the endometrial cavity in 78 percent at 2 weeks, 52 percent at 3 weeks, 30 percent at 4 weeks, and 10 percent at 5 weeks. Demonstrable uterine cavity contents are seen for up to 2 months following delivery. Belachew and colleagues (2012) used 3-dimensional sonography and visualized intracavitary tissue matter in a third on day 1, 95 percent on day 7, 87 percent on day 14, and 28 percent on day 28. By day 56, the small cavity was empty. Sohn and associates (1988) described Doppler ultrasound results showing continuously increasing uterine artery vascular resistance during the first 5 days postpartum.
Decidua and Endometrial Regeneration Because separation of the placenta and membranes involves the spongy layer, the decidua basalis is not sloughed. The remaining decidua has striking variations in thickness, it has an irregular jagged appearance, and it is infiltrated with blood, especially at the placental site (see Fig. 36-2). Within 2 or 3 days after delivery, the remaining decidua becomes differentiated into two layers. The superficial layer becomes necrotic and is sloughed in the lochia. The basal layer adjacent to the myometrium remains intact and is the source of new endometrium. This arises from proliferation of the endometrial glandular remnants and the stroma of the interglandular connective tissue. Endometrial regeneration is rapid, except at the placental site. Within a week or so, the free surface becomes covered by epithelium, and Sharman (1953) identified fully restored endometrium in all biopsy specimens obtained from the 16th day onward. Histological endometritis is part of the normal reparative process. Moreover, microscopic inflammatory changes characteristic of acute salpingitis are seen in almost half of women between 5 and 15 days, but these findings do not reflect infection (Andrews, 1951). Clinical Aspects Afterpains. In primiparous women, the uterus tends to remain tonically contracted following delivery. In multiparas, however, it often contracts vigorously at intervals and gives rise to afterpains, which are similar to but milder than labor contractions. These are more pronounced as parity increases and worsen when the infant suckles, likely because of oxytocin release (Holdcroft, 2003). Usually, afterpains decrease in intensity and become mild by the third day. We have encountered unusually severe and persistent afterpains in women with postpartum uterine infections. Lochia. Early in the puerperium, sloughing of decidual tissue results in a vaginal discharge of variable quantity. The discharge is termed lochia and contains erythrocytes, shredded decidua, epithelial cells, and bacteria. For the first few days after delivery, there is blood sufficient to color it red—lochia rubra. After 3 or 4 days, lochia becomes progressively pale in color—lochia serosa. After approximately the 10th day, because of an admixture of leukocytes and reduced fluid content, lochia assumes a white or yellow-white color—lochia alba. The average duration of lochial discharge ranges from 24 to 36 days (Fletcher, 2012).

NEWBORN

INITIATION OF AIR BREATHING
Immediately following birth, the infant must promptly convert to air breathing as the fluid-filled alveoli expand with air and pulmonary perfusion is established. The newborn begins to breathe and cry almost immediately after birth, which indicates establishment of active respiration. Some factors that appear to influence the first breath include: • Physical stimulation—examples include handling the neonate during delivery. • Oxygen deprivation and carbon dioxide accumulation—these serve to increase the frequency and magnitude of breathing movements both before and after birth (Dawes, 1974). • Thoracic compression—this occurs during pelvic descent, following which vaginal birth forces fluid from the respiratory tract in volume equivalent to approximately a fourth of the ultimate functional residual capacity (Saunders, 1978). • Aeration of the newborn lung does not involve the inflation of a collapsed structure, but instead, the rapid replacement of bronchial and alveolar fluid by air. After delivery, the residual alveolar fluid is cleared through the pulmonary circulation and to a lesser degree, through the pulmonary lymphatics (Chernick, 1978). Delay in fluid removal from the alveoli probably contributes to the syndrome of transient tachypnea of the newborn (TTN) (Guglani, 2008). As fluid is replaced by air, compression of the pulmonary vasculature is reduced considerably, and in turn, resistance to blood flow is lowered. With the fall in pulmonary arterial blood pressure, the ductus arteriosus normally closes (Fig. 7-8, p. 136). High negative intrathoracic pressures are required to bring about the initial entry of air into the fluid-filled alveoli. Normally, from the first breath after birth, progressively more residual air accumulates in the lung, and with each successive breath, lower pulmonary opening pressure is required. In the normal mature newborn, by approximately the fifth breath, pressure-volume changes achieved with each respiration are very similar to those of the adult. Thus, the breathing pattern shifts from the shallow episodic inspirations characteristic of the fetus to regular, deeper inhalations (Chap. 17, p. 337). Surfactant, which is synthesized by type II pneumocytes and already present in the alveoli, lowers alveolar surface tension and thereby prevents lung collapse. Insufficient surfactant, common in preterm infants, leads promptly to respiratory distress syndrome, which is described in Chapter 34 (p. 653).

CARE IN THE DELIVERY ROOM
 Personnel designated for infant support are responsible for immediate care and for acute resuscitation initiation if needed.
 Immediate Care
 Before and during delivery, careful consideration must be given to several determinants of neonatal well-being including: (1) maternal health status; (2) prenatal complications, including any suspected fetal malformations; (3) gestational age; (4) labor complications; (5) duration of labor and ruptured membranes; (6) type and duration of anesthesia; (7) difficulty with delivery; and (8) medications given during labor and their dosages, administration routes, and timing relative to delivery.
 Newborn Resuscitation
The International Liaison Committee on Resuscitation (ILCOR) updated its guidelines for neonatal resuscitation that are sanctioned by the American Academy of Pediatrics and the American Heart Association (Biban, 2011; Perlman, 2010). These substantially revised guidelines are incorporated into the following sections. Approximately 10 percent of newborns require some degree of active resuscitation to stimulate breathing, and 1 percent require extensive resuscitation. It is perhaps not coincidental that there is a two- to threefold risk of death for newborns delivered at home compared with those delivered in hospitals (American College of Obstetricians and Gynecologists, 2013b). When deprived of oxygen, either before or after birth, neonates demonstrate a well-defined sequence of events leading to apnea (Fig. 32-1). With oxygen deprivation, there is a transient period of rapid breathing, and if it persists, breathing stops, which is termed primary apnea. This stage is accompanied by a fall in heart rate and loss of neuromuscular tone. Simple stimulation and exposure to oxygen will usually reverse primary apnea. If oxygen deprivation and asphyxia persist, however, the newborn will develop deep gasping respirations, followed by secondary apnea. This latter stage is associated with a further decline in heart rate, falling blood pressure, and loss of neuromuscular tone. Neonates in secondary apnea will not respond to stimulation and will not spontaneously resume respiratory efforts. Unless ventilation is assisted, death follows. Clinically, primary and secondary apneas are indistinguishable. Thus, secondary apnea must be assumed and resuscitation of the apneic newborn must be started immediately.


Resuscitation Protocol
 The updated algorithm for newborn resuscitation recommended by ILCOR and the International Consensus on Cardiopulmonary Resuscitation is shown in Figure 32-2. Many of its tenets follow below.
Basic Measures
 The vigorous newborn is first placed in a warm environment to minimize heat loss, the airway is cleared, and the infant dried. Routine gastric aspiration has been shown to be nonbeneficial and even harmful (Kiremitci, 2011). And although previously recommended, there is no evidence that bulb suctioning for clear or meconium-stained fluid is beneficial, even if the newborn is depressed (Chap. 33, p. 638). With stimulation, the healthy newborn will take a breath within a few seconds of birth and cry within half a minute, after which routine supportive care is provided.
Assessment at 30 Seconds of Life. Apnea, gasping respirations, or heart rate < 100 bpm beyond 30 seconds after delivery should prompt administration of positive-pressure ventilation with room air (Fig. 32-3). Assisted ventilation rates of 30 to 60 breaths per minute are commonly employed, and the percent of oxygen saturation is monitored by pulse oximetry. At this point, supplemental oxygen can be given in graduated increasing percentages to maintain oxygen saturation (Spo2) values within a normal range (Vento, 2011). Adequate ventilation is indicated by improved heart rate. ventilation. The head should be in a sniffing position with the tip of the nose pointing to the ceiling. The neck should not be hyperextended. Assessment at 60 Seconds of Life. If the heart rate remains < 100 bpm, then ventilation is inadequate. The head position should be checked as shown in Figure 32-3, secretions cleared, and if necessary, inflation pressure increased. If the heart rate persists below 100 bpm beyond 60 seconds, tracheal intubation is considered. A number of conditions may be the cause of inadequate response, including the following: • Hypoxemia or acidosis from any cause • Drugs administered to the mother before delivery • Immaturity • Upper airway obstruction • Pneumothorax • Lung abnormalities • Meconium aspiration • Central nervous system developmental abnormality • Sepsis syndrome. Tracheal Intubation If bag-and-mask ventilation is ineffective or prolonged, tracheal intubation is then performed. Other indications include the need for chest compressions or tracheal administration of medications, or special circumstances such as extremely low birthweight or a congenital diaphragmatic hernia. A laryngoscope with a straight blade—size 0 for a preterm infant and size 1 for a term neonate—is introduced at the side of the mouth and then directed posteriorly toward the oropharynx as shown in Figure 32-4. The laryngoscope is next moved gently into the vallecula—the space between the base of the tongue and the epiglottis. Gentle elevation of the laryngoscope tip will raise the epiglottis and expose the glottis and the vocal cords. The tube is then introduced through the vocal cords. Gentle cricoid pressure may be useful. Tube sizes vary from 3.5 to 4.0 mm for term infants down to 2.5 mm for those < 28 weeks or < 1000 g.

DYSTOCIA

There are several labor abnormalities that may interfere with the orderly progression to spontaneous delivery. Generally, these are referred to as dystocia. Dystocia literally means difficult labor and is characterized by abnormally slow labor progress. It arises from four distinct abnormalities that may exist singly or in combination. First, expulsive forces may be abnormal. For example, uterine contractions may be insufficiently strong or inappropriately coordinated to efface and dilate the cervix—uterine dysfunction. Also, there may be inadequate voluntary maternal muscle effort during second-stage labor. Second, fetal abnormalities of presentation, position, or development may slow labor. Also, abnormalities of the maternal bony pelvis may create a contracted pelvis. And last, soft tissue abnormalities of the reproductive tract may form an obstacle to fetal descent. More simply, these abnormalities can be mechanistically simplified into three categories that include abnormalities of the powers—uterine contractility and maternal expulsive effort; the passenger—the fetus; and the passage—the pelvis. Common clinical findings in women with these labor abnormalities are summarized in Table 23-1.

TABLE 23-1. Common Clinical Findings in Women with Ineffective Labor

 Inadequate cervical dilation or fetal descent:

     Protracted labor—slow progress

     Arrested labor—no progress

     Inadequate expulsive effort—ineffective pushing

 Fetopelvic disproportion:

     Excessive fetal size

     Inadequate pelvic capacity

     Malpresentation or position of the fetus

 Ruptured membranes without labor

Dystocia Descriptors

Abnormalities that are shown in Table 23-1 often interact in concert to produce dysfunctional labor. Commonly used expressions today such as cephalopelvic disproportion and failure to progress are used to describe ineffective labors. Of these, cephalopelvic disproportion is a term that came into use before the 20th century to describe obstructed labor resulting from disparity between the fetal head size and maternal pelvis. But the term originated at a time when the main indication for cesarean delivery was overt pelvic contracture due to rickets (Olah, 1994). Such absolute disproportion is now rare, and most cases result from malposition of the fetal head within the pelvis (asynclitism) or from ineffective uterine contractions. True disproportion is a tenuous diagnosis because two thirds or more of women undergoing cesarean delivery for this reason subsequently deliver even larger newborns vaginally. A second phrase, failure to progress in either spontaneous or stimulated labor, has become an increasingly popular description of ineffectual labor. This term reflects lack of progressive cervical dilatation or lack of fetal descent. Neither of these two expressions is specific. Terms presented in Table 23-2 and their diagnostic criteria more precisely describe abnormal labor.

TABLE 23-2. Abnormal Labor Patterns, Diagnostic Criteria, and Methods of Treatment

Mechanisms of Dystocia

Dystocia as described by Williams (1903) in the first edition of this text is still true today. Figure 23-1 demonstrates the mechanical process of labor and potential obstacles. The cervix and lower uterus are shown at the end of pregnancy and at the end of labor.

At the end of pregnancy, the fetal head, to traverse the birth canal, must encounter a relatively thick lower uterine segment and undilated cervix. The uterine fundus muscle is less developed and presumably less powerful. Uterine contractions, cervical resistance, and the forward pressure exerted by the leading fetal part are the factors influencing the progress of first-stage labor.

FIGURE 23-1 Diagrams of the birth canal. A. At the end of pregnancy. B. During the second-stage of labor, showing formation of the birth canal. C.R. = contraction ring; Int. = internal; Ext = external. (Adapted from Williams, 1903.)

As also shown in Figure 23-1B, after complete cervical dilatation, the mechanical relationship between the fetal head size and position and the pelvic capacity, namely fetopelvic proportion, becomes clearer as the fetus descends. Because of this, abnormalities in fetopelvic proportions become more apparent once the second stage is reached. Uterine muscle malfunction can result from uterine overdistention or obstructed labor or both. Thus, ineffective labor is generally accepted as a possible warning sign of fetopelvic disproportion. Although artificial separation of labor abnormalities into pure uterine dysfunction and fetopelvic disproportion simplifies classification, it is an incomplete characterization because these two abnormalities are so closely interlinked. Indeed, according to the American College of Obstetricians and Gynecologists (2013), the bony pelvis rarely limits vaginal delivery. In the absence of objective means of precisely distinguishing these two causes of labor failure, clinicians must rely on a trial of labor to determine if labor can be successful in effecting vaginal delivery.

Revised Dystocia Diagnosis

In 2009, the total cesarean delivery rate for all births in the United States reached a record high of 32.9 percent (Martin, 2011). This was the 13th consecutive year in which the cesarean rate increased, and it represented a nearly 60-percent increase compared with 20.7 percent in 1996. The 2010 rate of 32.8 percent could suggest that this long trend of increasing cesarean rates may now be moderating (Martin, 2012). Given that many repeat cesarean deliveries are performed after primary operations for dystocia, it is estimated that 60 percent of all cesarean deliveries in the United States are ultimately attributable to the diagnosis of abnormal labor (American College of Obstetricians and Gynecologists, 2013). To address this increasing cesarean delivery rate, a workshop was convened by the National Institute of Child Health and Human Development (NICHD) and the American College of Obstetricians and Gynecologists (Spong, 2012). The workshop recommended new definitions for arrest of labor progress to prevent unnecessary first cesarean deliveries. Specifically, it concluded that “adequate time for normal latent and active phases of the first The Safe Labor Consortium report by Zhang and associates (2010) was a multicenter retrospective study using abstracted 2002 to 2008 data from electronic medical records in 19 hospitals across the United States. One purpose of this study was to analyze labor patterns and develop contemporary criteria for labor progress in nulliparas. Shown in Figure 23-2 is a synopsis of the study cohort, which formed the basis of the proposed new criteria for labor progress. Importantly, all women with cesarean delivery were excluded as were all of those with compromised newborn infants. Because of these major exclusions, the pattern of labor now defined as normal is problematic given that only women who achieved vaginal birth with a normal infant outcome were included. It is also problematic to conclude that these revised labor criteria will reduce the cesarean rate when the overall rate in the Safe Labor Consortium was 30.5 percent using the newly proposed first-stage labor intervals. The authors of a report from the Maternal Fetal Medicine Units Network of the NICHD analyzed labor management practices in 8546 women undergoing primary cesarean delivery for dystocia in a wide cross section of hospitals in the United States (Alexander, 2003). Approximately 92 percent of the cesareans for dystocia were performed in the active phase of labor defined as ≥ 4 cm cervical dilatation. The median admission to delivery interval was 17 hours, and the median cervical dilation was 6 cm before the dystocia diagnosis in women in active-phase labor. Oxytocin was used in 90 percent of women diagnosed with dystocia. It was concluded that bona-fide efforts were being made in contemporary practice to achieve active labor before diagnosing dystocia leading to cesarean delivery.

FIGURE 23-2 Study cohort for the analysis of spontaneous labor in the Safe Labor Consortium. NICU = neonatal intensive care unit. (Data from Zhang, 2010.)

The report by Rouse and colleagues (2009) on second-stage labor was a secondary analysis of 4126 nulliparous women who reached the second stage during a randomized trial to study fetal pulse oximetry. Of the 360 women—9 percent—whose second stage was > 3 hours, 95 percent had received epidural analgesia. A third of these 360 women—3.5 percent of the whole cohort—had a second stage > 4 hours. The results of this study were interpreted as support for extending the duration of the second stage in nulliparas to beyond the current recommended 3 hours when epidural analgesia is used (American College of Obstetricians and Gynecologists, 2013). The investigators concluded that a fetus born after a > 3-hour second stage had a higher—albeit still low—neonatal intensive care unit (NICU) admission rate and a low risk for brachial plexus injury (Rouse, 2009). These latter results are in contrast to those associated with prolonged second-stage labors at Parkland Hospital (Bleich, 2012). This study included 21,991 women of whom 7 percent had a second-stage labor > 3 hours. Most of the 2 percent of women reaching 4 hours in the second stage had been given epidural analgesia and were awaiting cesarean delivery that was decided on at the 3-hour time point. Typically, oxytocin had been discontinued, and they also had reassuring fetal heart rate tracings that permitted temporization awaiting operative space. Thus, such prolonged second stages were unintentional in that further efforts to effect vaginal delivery were not made. Despite these caveats, virtually every adverse infant outcome analyzed increased significantly when the second stage exceeded 3 hours in women with labor epidural analgesia (Table 23-5).

Relationship between First- and Second-Stage Labor Duration

It is possible that prolonged first-stage labor presages that with the second stage. Nelson and associates (2013) studied the relationships between the lengths of the first and second stages of labor in 12,523 nulliparous women at term delivered at Parkland Hospital. The length of the second stage significantly increased concomitantly with increasing length of the first stage. The 95th percentile was 15.6 and 2.9 hours for the first and second stages, respectively. Women with first stages lasting longer than 15.6 hr (> 95th percentile) had a 16.3 percent rate of a second-stage labor lasting 3 hr (95th percentile) compared with a 4.5-percent rate in women with first-stages labors lasting less than the 95th percentile.

Maternal Pushing Efforts

With full cervical dilatation, most women cannot resist the urge to “bear down” or “push” each time the uterus contracts (Chap. 22, p. 451). The combined force created by contractions of the uterus and abdominal musculature propels the fetus downward. Bloom and colleagues (2006) studied effects of actively coaching expulsive efforts. They reported that although the second stage was slightly shorter in coached women, there were no other maternal advantages. At times, force created by abdominal musculature is compromised sufficiently to slow or even prevent spontaneous vaginal delivery. Heavy sedation or regional analgesia may reduce the reflex urge to push and may impair the ability to contract abdominal muscles sufficiently. In other instances, the inherent urge to push is overridden by the intense pain created by bearing down. Two approaches to second-stage pushing in women with epidural analgesia have yielded contradictory results. The first advocates pushing forcefully with contractions after complete dilation, regardless of the urge to push. With the second, analgesia infusion is stopped and pushing begun only after the woman regains the sensory urge to bear down. Fraser and coworkers (2000) found that delayed pushing reduced difficult operative deliveries, whereas Manyonda and associates (1990) reported the opposite. Hansen and colleagues (2002) randomly assigned 252 women with epidural analgesia to one of the two approaches. There were no adverse maternal or neonatal outcomes linked to delayed pushing despite significantly prolonging second-stage labor. Plunkett and coworkers (2003), in a similar study, confirmed these findings.

Fetal Station at Onset of Labor

Descent of the leading edge of the presenting part to the level of the ischial spines (0 station) is defined as engagement. Friedman and Sachtleben (1965, 1976) reported a significant association between higher station at the onset of labor and subsequent dystocia. Handa and Laros (1993) found that fetal station at the time of arrested labor was also a risk factor for dystocia. Roshanfekr and associates (1999) analyzed fetal station in 803 nulliparous women at term in active labor. At admission, the third with the fetal head at or below 0 station had a 5-percent cesarean delivery rate. This is compared with a 14-percent rate for those with higher stations. The prognosis for dystocia, however, was not related to incrementally higher fetal head stations above the pelvic midplane (0 station). Importantly, 86 percent of nulliparous women without fetal head engagement at diagnosis of active labor delivered vaginally. These observations apply especially for parous women because the head typically descends later in labor.

Reported Causes of Uterine Dysfunction

Epidural Analgesia

Various labor factors have been implicated as causes of uterine dysfunction. Of these, epidural analgesia can slow labor (Sharma, 2000). As shown in Table 23-7, epidural analgesia has been associated with lengthening of both first- and second-stage labor and with slowing of the rate of fetal descent. This is documented further in Chapter 25 (p. 515). TABLE 23-7. Effect of Epidural Analgesia on the Progress of Labor in 199 Nulliparous Women Delivered Spontaneously at Parkland Hospital

Maternal Position During Labor 

Advocacy for recumbency or ambulation during labor has vacillated. Proponents of walking report it to shorten labor, decrease rates of oxytocin augmentation, decrease the need for analgesia, and lower the frequency of operative vaginal delivery (Flynn, 1978; Read, 1981). But other observations do not support this. According to Miller (1983), the uterus contracts more frequently but with less intensity with the mother lying on her back rather than on her side. Conversely, contraction frequency and intensity have been reported to increase with sitting or standing. Lupe and Gross (1986) concluded, however, that there is no conclusive evidence that upright maternal posture or ambulation improves labor. They reported that women preferred to lie on their side or sit in bed. Few chose to walk, fewer to squat, and none wanted the knee-chest position. They tended to assume fetal positions in later labor. Most women enthusiastic about ambulation returned to bed when active labor began (Carlson, 1986; Williams, 1980). Bloom and colleagues (1998) conducted a randomized trial to study the effects of walking during first-stage labor. In 1067 women with uncomplicated term pregnancies delivered at Parkland Hospital, these investigators reported that ambulation did not affect labor duration. Ambulation did not reduce the need for analgesia, nor was it harmful to the perinate. Because of these observations, we give women without complications the option to select either recumbency or supervised ambulation during labor. This policy is in agreement with the American College of Obstetricians and Gynecologists (2013), which has concluded that ambulation in labor is not harmful, and mobility may result in greater comfort.

Birthing Position in Second-Stage Labor

Considerable interest has been shown in alternative second-stage labor birth positions and their effect on labor. Gupta and Hofmeyr (2004) in their Cochrane database review compared upright positions with supine or lithotomy positions. Upright positions included sitting in a “birthing chair,” kneeling, squatting, or resting with the back at a 30-degree elevation. With these positions, they found a 4-minute shorter interval to delivery, less pain, and a lower incidence both of nonreassuring fetal heart rate patterns and of operative vaginal delivery. There was, however, an increased rate of blood loss > 500 mL with the upright positions. Berghella and colleagues (2008) hypothesized that parity, less intense aortocaval compression, improved fetal alignment, and larger pelvic outlet diameters might explain these findings. In an earlier study, Russell (1969) described a 20- to 30-percent increase in the area of the pelvic outlet with squatting compared with that in the supine position. Finally, Babayer and associates (1998) cautioned that prolonged sitting or squatting during the second stage may cause common fibular nerve neuropathy.

Water Immersion

A birthing tub or bath has been advocated as a means of relaxation that may contribute to more efficient labor. Cluett and coworkers (2004) randomly assigned 99 laboring women at term in first-stage labor identified to have dystocia to immersion in a birthing pool or to oxytocin augmentation. Water immersion lowered the rate of epidural analgesia use but did not alter the rate of operative delivery. More infants of women in the immersion group were admitted to the NICU. These findings were similar to their subsequent Cochrane database review, except that NICU admission rates were not increased (Cluett, 2009). Robertson and associates (1998) reported that immersion was not associated with chorioamnionitis or uterine infection. Moreover, Kwee and coworkers (2000) studied the effects of immersion in 20 women and reported that blood pressure decreased, whereas fetal heart rate was unaffected. Neonatal complications unique to underwater birth that have been described include drowning, hyponatremia, waterborne infection, cord rupture, and polycythemia (Austin, 1997; Pinette, 2004).

PREMATURELY RUPTURED MEMBRANES AT TERM

Membrane rupture at term without spontaneous uterine contractions complicates approximately 8 percent of pregnancies. Until recently, management generally included labor stimulation if contractions did not begin after 6 to 12 hours. This intervention evolved more than 50 years ago because of maternal and fetal complications due to chorioamnionitis (Calkins, 1952). Such routine intervention was the accepted practice until challenged by Kappy and colleagues (1979). These investigators reported excessive cesarean delivery in term pregnancies with ruptured membranes managed with labor stimulation compared with those expectantly managed. Subsequent research included that of Hannah (1996) and Peleg (1999) and their associates, who enrolled a total of 5042 pregnancies with ruptured membranes in a randomized investigation. They measured the effects of induction versus expectant management and also compared induction using intravenous oxytocin with that using prostaglandin E2 gel. There were approximately 1200 pregnancies in each of the four study arms. They concluded that labor induction with intravenous oxytocin was the preferred management. This determination was based on significantly fewer intrapartum and postpartum infections in women whose labor was induced. There were no significant differences in cesarean delivery rates. Subsequent analysis by Hannah and coworkers (2000) indicated increased adverse outcomes when expectant management at home was compared with in-hospital observation. Mozurkewich and associates (2009) reported lower rates of chorioamnionitis, metritis, and NICU admissions for women with term ruptured membranes whose labors were induced compared with those managed expectantly. At Parkland Hospital, labor is induced soon after admission when ruptured membranes are confirmed at term. The benefit of prophylactic antibiotics in women with ruptured membranes before labor at term is unclear (Passos, 2012).

PRECIPITOUS LABOR AND DELIVERY

Labor can be too slow, but it also can be abnormally rapid. Precipitous labor and delivery is extremely rapid labor and delivery. It may result from an abnormally low resistance of the soft parts of the birth canal, from abnormally strong uterine and abdominal contractions, or rarely from the absence of painful sensations and thus a lack of awareness of vigorous labor. According to Hughes (1972), precipitous labor terminates in expulsion of the fetus in < 3 hours. Using this definition, 89,047 live births—2 percent—were complicated by precipitous labor in the United States during 2006 (Martin, 2009). Despite this incidence, there is little published information concerning adverse effects.

Maternal Effects

Precipitous labor and delivery seldom are accompanied by serious maternal complications if the cervix is effaced appreciably and compliant, if the vagina has been stretched previously, and if the perineum is relaxed. Conversely, vigorous uterine contractions combined with a long, firm cervix and a noncompliant birth canal may lead to uterine rupture or extensive lacerations of the cervix, vagina, vulva, or perineum. It is in these latter circumstances that the rare condition of amnionic-fluid embolism most likely develops (Chap. 41, p. 812). Precipitous labor is frequently followed by uterine atony. The uterus that contracts with unusual vigor before delivery is likely to be hypotonic after delivery. Postpartum hemorrhage from uterine atony is discussed in Chapter 41 (p. 784). Mahon and colleagues (1994) described 99 pregnancies delivered within 3 hours of labor onset. Short labors were defined as a rate of cervical dilatation of 5 cm/hr or faster for nulliparas and 10 cm/hr for multiparas. Such short labors were more common in multiparas who typically had contractions at intervals less than 2 minutes and were associated with placental abruption, meconium, postpartum hemorrhage, cocaine abuse, and low Apgar scores.

Fetal and Neonatal Effects

Adverse perinatal outcomes from precipitous labor may be increased considerably for several reasons. The tumultuous uterine contractions, often with negligible intervals of relaxation, prevent appropriate uterine blood flow and fetal oxygenation. Resistance of the birth canal may rarely cause intracranial trauma. Acker and coworkers (1988) reported that Erb or Duchenne brachial palsy was associated with such labors in a third of cases (Chap. 33, p. 648). Finally, during an unattended birth, the newborn may fall to the floor and be injured, or it may need resuscitation that is not immediately available.

Treatment

Unusually forceful spontaneous uterine contractions are not likely to be modified to a significant degree by analgesia. The use of tocolytic agents such as magnesium sulfate is unproven in these circumstances. Use of general anesthesia with agents that impair uterine contractibility, such as isoflurane, is often excessively heroic. Certainly, any oxytocin agents being administered should be stopped immediately.