Normal Labor and Delivery
Table Of Contents
Lisa Harrington, CNM, MPH, MSN, MA
DEFINITION OF LABOR
MANAGEMENT OF LABOR
ALTERNATE OBSTETRIC MANAGEMENT MODELS: MIDWIFERY
In the last 25 years there has been a steady increase in the rate of cesarean births, from 5.5% in 1970, to approximately 25% in 1995.1 This increase has occurred as a result of changes in the management of several factors, including malpresentation, fetal distress, prior cesarean section, and dystocia. The increase in the cesarean section rate has not been a major contributing factor in decreasing the perinatal mortality rate, which has occurred during the same period of time. In view of this increase in the cesarean section rate, it is essential that all medical personnel participating in the care of a laboring patient have a complete knowledge of the principles of management of normal labor and delivery. This knowledge will help prevent the necessity for cesarean sections by optimizing the care of laboring patients.
In this chapter we review the process of normal labor and delivery. The definition and etiology of labor are presented, followed by a discussion of the course of normal labor. A discussion of alternate approaches of labor management and controversial issues is also included.
|DEFINITION OF LABOR|
Labor is defined as the presence of regular uterine contractions with progressive cervical dilation and effacement. During the last month of gestation, several physiologic changes precede the onset of labor. Most patients report an increase in the incidence of Braxton Hicks contractions. These usually are irregular in frequency and intensity. Many nulliparous patients have difficulty distinguishing between the increased incidence of the Braxton Hicks contractions and the onset of early labor. Besides the irregular nature of the Braxton Hicks contractions, they are also characterized by their origination from diverse areas in the uterus. This contrasts with true labor, in which the contractions usually originate from the uterine fundus and extend downward toward the cervix. It is difficult, if not impossible, to determine the exact moment of transition from Braxton Hicks contractions to the onset of true labor. The clinician monitors major parameters, such as the presence of changes in cervical effacement, dilation, position, consistency, and descent of the presenting part to determine when this transition takes place.
Concomitant with the increased frequency of contractions, the patient may perceive descent of the fetus into her pelvis. This is referred to as lightening. This process will happen as the lower uterine segment expands due to the increase in frequency and intensity of contractions. As the presenting part descends into the maternal pelvis, it can apply significant pressure onto the sacrum and can exacerbate any chronic lumbosacral pain, or even originate such problems. Some patients experience sciatic nerve pain secondary to this anatomic change of pregnancy. In addition, lightening results in increased pressure on the maternal bladder, thus increasing the symptoms of urinary frequency.
The cervical changes associated with early labor involve the process of effacement, in which the cervix is incorporated into the lower uterine segment. This forces the cervical mucous plug out of the cervix. This plug consists of a tenacious mucous produced by the hypertrophied endocervical glands. It serves as both a mechanical and immunologic barrier to any ascending pathogens from the vagina. During the process of cervical effacement and dilation, some capillary blood vessels will rupture. This small amount of bleeding will give a bloody appearance to the mucous plug. This is commonly referred to as the “bloody show.” In the presence of regular contractions and effacement, the passage of the bloody show should be considered an indication of the onset of labor.2
There is no universal agreement about the series of events that triggers the onset of human parturition. Although several mechanisms have been postulated, what follows is a recently described theory that incorporates most of the factors that have been identified as possible causes of the onset of labor.3,4,5
During the last trimester of pregnancy, the process of cervical growth and remodeling is accelerated. This process is under the influence of the placental hormones and relaxin. Prostaglandin E2 (PGE2) acts synergistically with these substances to promote cervical change. At the end of gestation there is increased production of PGE2. Concomitantly, there is an increase in the production and concentration of oxytocin receptors. The number of receptors increases with uterine distention. This also causes an increase in the number of myometrial gap junctions. As a result of these last two events, there is an increased response by the myometrium to the oxytocin pulses secreted by the posterior pituitary, which then causes an increase in the frequency and intensity of the contractions. This generates greater pressure and tension on the cervix, which further increases the production of PGE2. This is followed by an increasing frequency of oxytocin pulses that increases the frequency of contractions. The decidua then responds to the oxytocin by releasing PGF2a, which increases the response to oxytocin by the myometrium.
At this point, maturational changes in the placenta and fetus cause the release of a diverse number of substances from several organs. This includes epidermal growth factor, platelet-activating factor, adrenocorticotropic hormone, stress hormones, vasopressin, and increased amounts of oxytocin. The release of some of these substances is caused by the stress of the transient decrease in fetal oxygenation due to the increased frequency of uterine activity. As a result of the release of these substances, additional mobilization of arachidonic acid from the uterine phospholipids occurs. This causes an increase in the release of prostaglandins from the placental membranes during the contractions. This, in turn, is a further stimulus for increased uterine activity. In this way, this process creates a continuous cycle of activity that results in the development of labor.
|MANAGEMENT OF LABOR|
Admission to Labor and Delivery
A patient who presents to a labor and delivery unit with symptoms of labor should have a thorough and systematic evaluation. The evaluating clinician should first make a rapid assessment of the clinical situation. If there are no signs of an obstetric emergency (e.g., vaginal bleeding, severe hypertension, shock), the clinician should continue with a careful history and physical examination. A complete history should be obtained, including past obstetric, gynecologic, medical, and surgical problems. Allergies should be noted clearly. The social history should be evaluated for the presence of toxic habits. The family history may suggest hereditary or multifactorial problems that could have an impact on the present pregnancy. Any current medications and their indications must be recorded. All of these components of the history should be obtained, even if they already were obtained and documented during the prenatal period. If the patient had prenatal care, careful attention should be given to any complications that may have developed (e.g., gestational diabetes, anemia). It is customary to document any prenatal laboratory results or testing. This provides the clinician with additional tools to evaluate the patient at the moment of admission. Any problems identified during the history should be evaluated for any possible impact on the course of labor, the delivery, and the neonate.
The physical examination for a patient being admitted to a labor and delivery unit should be as thorough as that for any patient being admitted to any other acute-care ward. After the vital signs are obtained, a systematic examination is rendered, the pelvic examination being reserved for last. During the abdominal examination, the clinician performs Leopold's maneuvers. This, in conjunction with the pelvic examination, allows the clinician to assess the fetal lie, presentation, and position. Careful attention should be given to the identification of any abnormalities, such as uterine tenderness, fibroids, or possible malpresentations. During the abdominal examination, the clinician should assess the fetal heart tones, using either a DeLee fetoscope or a Doppler device. If there are any difficulties obtaining the fetal heart tones, an ultrasound examination must be performed immediately. During the pelvic examination, the clinician assesses the type of pelvis. The cervix is palpated for the presence of dilation and effacement. During the pelvic examination, the station of the presenting part can be determined. The cervical examination should be plotted on graph paper (i.e., a partogram) for serial evaluation of the progress of labor. The cervical dilation is plotted on the vertical axis. The longitudinal axis is used to record time in hours (Fig. 1). Some partograms include a double vertical axis, so that dilation and fetal station can be plotted simultaneously over time (Fig. 2). By the end of the examination, the clinician should be confident of his assessment of the fetal presentation. If not, or if any other clinical indications are present, an ultrasound examination should be performed.
Occasionally, a patient presents in advanced labor. There might not be enough time to do a complete history and physical examination before the delivery. The clinician must make judgments based on the clinical situation and defer parts of the admission examination to after the delivery. No patient should be permitted to leave the labor and delivery unit without a complete examination.
Once the patient's history and physical are obtained and recorded, an assessment of the patient's risk status and labor situation is made so that the care of the patient can be individualized. Each institution should have a formal designation of what type of forms will be used for this purpose. In the United States, it is customary to obtain intravenous access on most laboring patients, although midwife nurses will frequently abstain from doing so. Some patients may request a heparin lock for more comfortable ambulation during early labor. If this is the case, intravenous solutions should be started at the earliest signs of dehydration or the development of a complication. At the same time intravenous access is obtained, a blood sample can be obtained for a complete blood count and for a type and screen. Besides the blood sample, a urine specimen is obtained for protein and glucose determination. If the laboring patient did not have prenatal care, the complete panel of routine maternal prenatal laboratory tests should be ordered. This panel can vary among institutions and types of patient populations.
During the course of labor, the fetus is monitored by either continuous or intermittent auscultation. In the United States, the majority of hospital births attended by physicians are monitored electronically. Further assessment of the fetus can be obtained from the quality of the amniotic fluid. If it is meconium stained, careful attention should be given to any abnormal fetal heart patterns. The presence of meconium suggests the possibility of a compromised fetus. If circumstances were to allow it, an ultrasound assessment for estimated fetal weight would provide the clinician with helpful information to assess the clinical situation.DeLee suctioning of the fetus at birth is essential in cases of meconium stained amniotic fluid, as is the presence of medical personnel trained to perform neonatal intubation.
Most of the discussion on the stages of labor that follows is based on the scholarly contributions of Friedman, who for the last four decades has documented the normal and abnormal patterns of human labor.
The first stage of labor is the period of time from the onset of labor to complete cervical dilation. This stage is divided into latent and active phases. The active phase is further subdivided into the acceleration, maximum slope, and deceleration phases of dilation.
The latent phase is the longest of all the phases of the first stage (Table 1). It has been determined that there is a negative correlation between the length of this phase and the amount of cervical dilation at the moment of onset of labor.6,7 Although multiparous patients appear to have shorter latent phases than nulliparous ones, this has not been a consistent finding.7
* 5th or 95th percentile.
(Modified from Friedman EA: Labor: Clinical Evaluation and Management, p23, 2nd ed. New York, Appleton-Century-Crofts, 1978)
The “transition” from the latent to the active phase is sometimes a very difficult one to identify. Some patients have a transition of labor while manifesting increased levels of pain and discomfort. Not infrequently, some have emesis as the cervix starts dilating at a faster rate. This probably is due to the stimulation of vagal nerve endings present in the cervix. The use of epidural anesthesia also makes this transition more clinically difficult to assess without the performance of a cervical examination. Although the transition from latent to active phase is difficult to identify, a dilation of 3 cm is accepted as the point beyond which the rate of dilation should increase to the rate expected in the active phase7: 1.2 cm/hour in the nulliparous patient and 1.5 cm/hour in the multiparous patient.8
The acceleration phase is clinically very difficult to document unless the clinician is performing frequent serial vaginal examinations. It encompasses the period shortly before the phase of maximum slope. In the nulliparous patient, this is compatible with a cervical dilation of 3 to 5 cm. In clinical practice, there will be a significant degree of variation in the length of this phase.
Maximum Slope Phase.
This phase has the most rapid rate of cervical dilation during labor. It typically occurs during dilation from 5 to 8 cm. According to Friedman,9 the plotting of the rate of dilation during this phase reveals a linear relationship. Other authors have suggested that the labor curve during this phase is hyperbolic.10,11 This is based on observations that reflected a constantly increasing rate of dilation as dilation progressed. The rate of dilation during the active phase is currently accepted to reflect a linear relationship. It is important for the clinician to be aware that it is during this phase that the descent of the presenting part will begin.12
The existence of the deceleration phase has been questioned.11 The debate on its existence is complicated by the short length of this phase, which is shorter than the length of the acceleration phase and easily missed if the cervical examinations are done infrequently. This phase rarely lasts more than 3 hours in a nullipara or 1 hour in a multipara. It usually extends from 8 to 9 cm until cervical dilation is complete. The descent curve reaches its maximum slope concomitant with the deceleration phase.13 The normal rate of descent of the presenting part is at least 1 cm/hour in the nullipara or 2 cm/hour in the multipara.
The second stage of labor is the period of time from complete cervical effacement to the delivery of the fetus. The presenting part is expected to descend at the same rate as during the deceleration phase.
The third stage of labor is the period of time from the delivery of the fetus to the delivery of the placenta. There are several signs associated with the separation of the placenta from the wall of the uterus. The uterus becomes globular, and there is a sudden gush of blood. This is followed by the umbilical cord's extending more toward the vagina and introitus. During this process, some clinicians massage the uterus using the Brandt-Andrews maneuver and maintain a steady pull on the umbilical cord. Any excessive tension on the umbilical cord could cause evulsion of the umbilical cord from its placental insertion, requiring manual removal of the placenta. Uterine inversion is another complication derived from overaggressive uterine massage and excessive tension on the umbilical cord. Placenta accreta also has been associated with this problem. If uterine inversion occurs, rapid correction of the inversion is essential. To decrease overall blood loss, the placenta should be removed after the uterus is returned to the abdomen. Subsequent to the correction of the inversion, uterotonic agents should be administered. The agents typically used are methylergonovine or prostaglandins. A more rapid action of these agents is seen if they are administered directly intramyometrially rather than intramuscularly. Many institutions routinely use a diluted intravenous oxytocin solution after the delivery of the placenta. Oxytocin should not, however, be administered as a direct intravenous bolus because it is associated with hypotension.14
The signs of separation of the placenta usually become evident within 5 to 10 minutes after birth. Classically, failure to deliver the placenta after a period of 30 minutes or more is defined as a retained placenta. This would justify a manual removal. If the patient is not having excessive blood loss, it is advised that the clinician wait for adequate sedation before performing the removal. This can be accomplished with a combination of narcotics and benzodiazepines, or under regional anesthesia if it was used for pain control during labor and delivery. In an emergency, however, the removal may have to be performed without analgesia.
During or after the delivery of the placenta, it is important that the patient be examined for any lacerations or hematomas. A first degree laceration involves the vaginal mucosa and perineal skin, leaving intact the muscle and fascia. In a second degree laceration, there is involvement of the perineal muscles but not of the rectal sphincter. A fourth degree laceration includes involvement of the rectal mucosa. Any patient with a significant laceration requires a pelvic examination several hours after the repair to exclude the possibility of a hematoma. In addition, all patients who had an episiotomy or laceration at the moment of delivery, should have a gentle manual examination of the repair and visual examination of the perineum before being discharged from the hospital. The patient should be instructed on the warning signs of episiotomy breakdown or infection. Table 2 describes the advantages and disadvantages of different types of episiotomies.
Active Management of Labor
The active management of labor (AMOL), was first described in 1969 by O'Driscoll and colleagues.2 It was originally conceived as a technique for the prevention of prolonged labor, originally defined by the authors as more than 24 hours of labor, and in later publications as 12 hours. More recently,AMOL has been found to be a highly successful method for the prevention of labor dystocia and operative delivery.2,16,17,18 This technique was first implemented at the National Maternity Hospital in Dublin, Ireland, in 1968. Within the past 27 years, their total cesarean section rate has remained less than 10%.
The basic principles of AMOL involve the education of patients, attention to the accurate diagnosis of labor, close nursing or midwife support during labor, early amniotomy, early use of relatively high doses of oxytocin for the correction of labor abnormalities, and rigorous peer review.
In most of the published trials on AMOL, the criterion for patient enrollment has been as follows: term pregnancy (a minimum of 37 weeks), singleton, vertex presentation, nullipara, and spontaneous onset of labor.16,17,18 To our knowledge, there are no peer-review published reports documenting the use of this technique on multiparas or for induction of labor.
A very concise and clear description of the labor and delivery process is given to the patient during prenatal care visits. She is completely familiarized with all the principles of AMOL, and all of her doubts or concerns will have been answered before she is admitted to the labor and delivery unit. If there are no unexpected events, the patient is expected to have less anxiety regarding her labor, thus allowing her to develop a more comfortable attitude toward her labor process.
When patients are more aware of their labor process, unnecessary visits to labor and delivery for evaluation of possible labor can be prevented. In AMOL protocol, labor is defined as regular painful contractions in a frequency of at least one every 5 minutes. In addition to this, the patient should have at least one of the following three criteria: spontaneous rupture of membranes, complete cervical effacement, or the passage of bloody show. The evaluation of labor is carried out within 1 hour of the arrival of the patient to the unit. Every attempt is made to prevent having a patient walking for a prolonged period of time while still under evaluation for labor. If the patient does not meet the above criteria, she is encouraged to go home and to return when the labor symptoms are more intense.
One of the most important aspects of the AMOL protocol is the close support during labor. AMOL does not imply a more aggressive or interventional attitude toward labor, but an active involvement and awareness of the medical personnel with the events of a laboring patient. At the National Maternity Hospital, the nursing personnel perform duties similar to a midwife. This is done in close collaboration with the obstetrician-gynecologist. The nurse-to-patient ratio is 1:1. Every attempt is made to have a nurse attend a patient at all times. The nurse should be intimately aware of the progress and status of the patient. If there are any signs of an abnormality, she assesses the situation and consults the attending physician. Along with this, the constant presence of the nurse provides the patient with the so-called Dulla effect. “Dulla” refers to a constant companion of a laboring patient. This companion provides psycho-social support, with the goal of decreasing anxiety and stress during labor. The exact mechanism of action of the “Dulla” effect is unknown. This effect by itself has been found to be associated with a decreased incidence of cesarean section.19 The degree of participation of nurses is not limited only to labor management: Nurses also are permitted to deliver low-risk patients under the supervision of the attending obstetrician. These aspects of AMOL have made it difficult to implement in US hospitals. Several US hospitals have adopted the AMOL protocol, but not with the same degree of success as in Ireland. It is possible that if AMOL is implemented in US hospitals in association with midwives, it could achieve even better success.
Once the diagnosis of labor is made, an amniotomy is performed within 1 hour. Obviously, this should not be performed if the vertex is high and unengaged. With careful attention to the station of the vertex, the likelihood of an umbilical cord prolapse is rare.17 There are several reasons to perform early amniotomy. It allows the clinician to assess the quantity and quality of the amniotic fluid. The clinician would have a higher level of suspicion for the presence of a compromised fetus if scanty and thick, meconium-stained amniotic fluid was identified; this would also lead to a different approach to the labor management of the patient. Moreover, although it has been a source of debate in the literature, early amniotomy is generally considered to accelerate the labor process. A recent review20 of the literature on the effects of routine amniotomy on labor reached several important conclusions:
Without a comprehensive labor management plan, such as AMOL,21 the amniotomy may indeed fall short of having the impact of decreasing the incidence of cesarean deliveries. The amniotomy may increase the incidence of intrapartum abnormal fetal heart rate patterns, specifically variable decelerations, but this has not resulted in an increased incidence of low Apgar scores, neonatal acidosis, or morbidity.
After the amniotomy is performed, the patient is examined hourly for 3 hours, and then every 2 hours until delivery. This frequency of examinations has not resulted in an increased incidence of chorioamnionitis or postpartum endometritis. The goal of this close monitoring of the labor progress is to detect any dysfunctional pattern early. It is thought that with early detection and an attempt to correct a dysfunctional pattern of labor, there would be a higher likelihood of successfully correcting the abnormality, thus decreasing the need for operative delivery.
The ideal rate of progress under the AMOL protocol is 1 cm/hour during the first stage. The second stage is expected to last no more than 2 hours. A labor pattern associated with a rate of progress slower than this would require careful evaluation for a cause of such an abnormality. If the etiology is thought to originate from a dysfunctional pattern of uterine contractions, then oxytocin augmentation would be indicated.
The AMOL oxytocin augmentation protocol uses relatively higher doses compared with other protocols currently used in clinical practice.22 The protocol consists of an initial rate of 6 mU/minute, which is increased by increments of 6 mU/minute, to a maximum rate of 36 mU/minute. The optimal frequency of contractions with this augmentation protocol is seven in 15 minutes. The major goal of the use of higher dosages of oxytocin is to correct a dysfunctional pattern of labor before an intractable uterine dystocia becomes established. The oxytocin augmentation is limited to a period of 6 hours. Any patient that requires longer augmentation is thoroughly evaluated for factors other than dysfunctional uterine contractions that could account for the labor dystocia.
The major concerns regarding this augmentation protocol have centered on the issues of possible morbidity and mortality to either the mother or the fetus. Maternal issues include tachysystolic and tetanic uterine contractions, placental abruption, uterine rupture, postpartum uterine atony, and the need for transfusion. Fetal/neonatal issues include intrapartum meconium, fetal distress, acidosis, low Apgar scores, hyperbilirubin levels, admission to the neonatal intensive-care unit, seizures, death, and length of hospitalization. Several investigators have reported on the lack of association between AMOL augmentation and these factors.17,23,24 The use of relatively higher levels of oxytocin for augmentation of labor is not associated with a higher incidence of morbidity when compared with protocols that use oxytocin in a more conservative method. Of interest, the group at the National Maternity Hospital reported on more than 30,000 nulliparous patients who had AMOL according to the outlined protocol.24 There were no cases of uterine rupture secondary to the higher levels of oxytocin.
The use of AMOL has not resulted in a higher utilization of analgesia or anesthesia during labor.17 Patients can have intravenous sedation and regional blocks as judged clinically necessary.
No method of labor management or augmentation can eliminate the problem of labor dystocia. Even with AMOL, the clinician will have to determine when the augmentation is considered unsuccessful and an operative delivery indicated. If there is minimal or no dilation after 1 hour of optimal augmentation during the first stage, the clinician may consider proceeding with a cesarean section. Lack of descent after 1 hour of optimal augmentation during the second stage in the presence of optimal maternal pushing efforts is also an indication to proceed with an operative delivery, either vaginally or abdominally. Obviously if the patient has an arrest of dilation or descent disorder but an adequate pattern of spontaneous uterine contractions, the above indications for operative intervention would still apply. Whether and when to use an intrauterine pressure monitor for assessment of a dysfunctional labor is a clinical decision. The AMOL protocol neither requires nor excludes the use of this type of monitoring.
It has been demonstrated that the AMOL technique results in a shorter length of total labor. As a consequence of this, there is a decrease in the incidence of infectious problems, such as chorioamnionitis or endometritis.17 The incidence of labor dystocia also is diminished, resulting in a lower rate of operative delivery. This is accomplished with no increase in maternal or neonatal morbidity. These benefits also may translate into better utilization of the resources of the labor and delivery unit, as well as potential savings to the patient and society.
|ALTERNATE OBSTETRIC MANAGEMENT MODELS: MIDWIFERY|
Historically, midwives have managed and attended the majority of births and have had primary responsibility for the care of mothers and infants through the perinatal period. Nearly 75% of all births in third-world countries are attended by women whom the World Health Organization (WHO) has termed traditional birth attendants (TBA).25 The WHO has actively promoted TBA training by professional midwives for the purpose of more efficient utilization of health-care services to improve maternal and infant mortality rates. This model allows obstetricians to focus on the care of complicated pregnancies.
Professional midwives (many of whom are nurse-midwives) attend up to 75% of all births in European nations. In the past few years in the United States, midwives (predominantly nurse-midwives) have attended a small, but growing, number of births (4%).26,27 All of the countries with infant mortality rates that are lower than US rates utilize midwives as the principal birth attendants. In addition, the majority of the 18 industrialized nations with cesarean rates that are lower than US rates utilize midwives as primary caregivers for low-risk pregnant women. Universal access to prenatal care, primarily provided by midwives, is also a shared characteristic of the industrialized countries whose cesarean and infant mortality rates are lower than those of the United States.
The salient characteristics common in midwifery models of care include the use of minimal technology, time-intensive supportive care, the encouragement of maternal ambulation and multiple positions for labor and delivery, the minimal use of routine episiotomies and routine intravenous hydration, and the liberal use of comfort measures (massage, hydrotherapy, position change) to reduce the need for obstetric analgesia or anesthesia. The literature demonstrates that this model of management of normal labor and delivery is associated with lower rates of cesarean section, decreased rates of episiotomies and third- or fourth-degree lacerations, and infant morbidity and mortality rates comparable to or lower than those for similar low-risk populations managed by physicians. A study comparing labor-and-delivery management between nurse-midwives and family physicians showed that, despite similar management styles, nurse-midwives were more likely to facilitate a vaginal delivery and to do so without an episiotomy.28
Impact of Low Technology and Time-Intensive Supportive Care
The American College of Nurse-Midwives (ACNM), the national credentialing organization for US nurse-midwives, developed the ACNM Position Statement on the Appropriate Use of Technology in Childbirth,29 which describes the philosophy guiding the practice of most midwives:
One of the hallmarks of midwifery management is time-intensive supportive care, which has been shown to be associated with lower rates of labor abnormalities, cesarean sections, and fetal distress.30 This is consistent with earlier studies by Sosa and co-workers,31 which demonstrated shortened labor and lower rates of intervention in patients who had a supportive companion throughout labor. Midwifery management involves encouragement of active involvement of birth companions chosen by the patient, as well as frequent supportive midwifery interactions.
Several major studies involving birth center management (both in and out of hospitals) have evaluated the characteristics and effects of the midwifery model of care. Fullerton and Severino32 compared groups of women who were cared for principally by nurse-midwives in hospital and freestanding birth-center settings; even when controlling for complications and sociodemographic differences, they found that women in hospitals were more likely to receive an interventive style of labor and delivery management. Both groups had similar low rates of neonatal and maternal morbidity, but the incidences of sustained fetal distress, prolapsed cord, and difficulty in establishing neonatal respirations were significantly greater in the hospital sample. The National Birth Center Study33,34 involved 11,814 women admitted for labor and delivery to 84 freestanding birth centers in the United States. CNMs provided care during 78.6% of the labors and attended 80.6% of the births. Birth-center care deviated from hospital-based medical management care in that women were much less likely to receive narcotics, anesthesia, continuous electronic fetal monitoring, induction of labor, augmentation of labor, intravenous infusions, amniotomies, and episiotomies. In addition, relatively few vaginal examinations were performed, and the patients were more likely to be permitted to use a variety of birthing positions, to eat solid or clear food, and to take showers or baths during labor. The rate of cesarean section was 4.4%. There were no maternal deaths. The overall intrapartum and neonatal mortality rate was 1.3 per 1000 births. The rates of low Apgar and infant mortality were comparable to those reported in large studies of low-risk hospital births.
Greulich and colleagues35 reported on more than 30,000 nurse-midwife—attended births at the Los Angeles County/University of Southern California Women's Hospital, in which expectant midwifery management was the norm. Their findings are highlighted as follows:
Intrapartum maternal or neonatal deaths: 0%
The transfer rate to medical management from 1985 to 1992 was 13.1%, the most common indication being failure to progress and the consequent requirement of oxytocin augmentation. The patients who were transferred from a midwife to a physician's care service at the same institution were not included in the statistics provided by Greulich and colleagues.
Midwifery management advocates the liberal use of intermittent external fetal monitoring when one-to-one staffing permits. Several randomized clinical trials have not supported the routine use of continuous electronic fetal monitoring in low-risk pregnancies. Often, an initial 20-minute fetal heart rate tracing is obtained at admission to evaluate whether there is any evidence of fetal stress.
Maternal Ambulation and Position
Research has shown that maternal position effects the frequency and intensity of uterine contractions during labor. Caldeyro-Barcia and colleagues36 demonstrated that lateral positions were associated with more effective uterine contractions (i.e., stronger intensity and lower frequency) than the supine position; this effect was more marked in spontaneous labor compared with oxytocin-induced labor. The influence of position change on maternal hemodynamic changes also has been studied. There is evidence that lateral positions are associated with a higher cardiac output, decreased heart rate, and increased stroke volume compared with the supine position.37 Several reports indicate that intrapartum ambulation may improve labor. A randomized trial of ambulation versus oxytocin for labor enhancement38 indicated that, in relation to labor progress and initial effects on uterine activity, ambulation can be as effective as oxytocin in stimulating labor. Squatting has been advocated to increase the diameter of the pelvic outlet by as much as 2.0 cm, to increase the bearing-down urge, to facilitate the delivery of the placenta, and to prevent supine hypotensive syndrome. In addition, standing, kneeling, squatting, and lateral positions have been associated with maintaining an intact perineum. This results from a more even application of the fetal head at the introitus, which distributes pressure across the perineum, rather than concentrating the pressure at a single point. In the absence of maternal or fetal contraindications, Roberts39 described a current consensus in the literature supporting the advantages of upright positions in early labor; he advised that prolonged use of recumbent positions be minimized and that lateral, Sims, hands and knees, and supported squatting positions be considered for labor and delivery. Maternal comfort and preferences should be given priority when positions for labor and delivery are recommended. Unfortunately, the use of regional anesthesia during labor (epidural) can significantly limit the ambulation capabilities of the laboring patient. Similarly, high-risk patients may not be able to ambulate because of the need for continuous fetal or maternal monitoring.
Alternatives to Analgesia/Anesthesia in Pain Management
Thorp and associates40 undertook a randomized, controlled prospective trial to determine the effect of epidural anesthesia on nulliparous labor. Women were randomized to receive either narcotic or epidural anesthesia in early spontaneous labor. The study demonstrated a significant prolongation in the first and second stages of labor and a significant increase in the frequency of cesarean delivery. A recent meta-analysis published by Morton and co-workers41 strongly supported previous findings that a significant increase in cesarean delivery is associated with epidural anesthesia use. These results support the evidence that one factor leading to the decreased incidence of cesarean section in midwifery-managed patients lies in the lower rates of epidural use among midwifery patients. Petrie and colleagues42 presented evidence of increased uterine activity over time in unmedicated labor; they also discussed the depressant effect of narcotic administration on uterine activity. These studies support the predominant style of midwifery management of normal labor, which optimizes uterine effectiveness while minimizing risks through a minimal use of anesthesia and analgesia.
There has been a dearth of literature investigating the effect of alternative methods for pain management in labor. Specific areas of interest involve the effects of acupuncture, acupressure, and water immersion (hydrotherapy) on labor. Several investigators43,44 have reported beneficial effects in pain management in labor afforded by hydrotherapy. Water temperatures of less than 100°F are recommended. Conflicting evidence exists regarding the effects of warm water immersion on labor progress. Most studies demonstrated no evidence of increased maternal, neonatal, or infectious morbidity. There have been few case reports of neonatal death in water immersion at delivery when the infant was not immediately brought to the surface; however, no neonatal deaths have been reported in the literature when water immersion was utilized in labor alone. Because of the lack of published randomized, controlled clinical trials, caution is recommended when any of the above methods are attempted.
Fluids in Labor: Should Intravenous Hydration Be Used Routinely?
Fasting in labor has been an established practice throughout the United States since the 1940s. The major reason for this approach is the increased gastric emptying time that is present during labor. A laboring patient with a full stomach is at risk of developing an aspiration pneumonia secondary to vomiting during intubation for the administration of general endotracheal anesthesia. The questioning of routine intravenous hydration has arisen, in part, because of the decreased use of general anesthesia for deliveries and the increased use of regional anesthesia.45 Nevertheless, aspiration pneumonia remains the main cause of anesthesia-related deaths. It should be noted that fasting does not guarantee prevention of emesis and aspiration.
Episiotomies: Should They Be Used Routinely to Reduce the Occurrence of Perineal Lacerations?
Episiotomy is one of the most common surgical procedures in Western medicine. Thacker and Banta46 published an extensive literature review describing the benefits and risks of episiotomy as known up to 1983. The authors reported that there was no clearly defined evidence supporting the efficacy of episiotomies, especially with respect to routine use. They provided evidence that postpartum perineal pain and lacerations involving the anus may be increased after episiotomy and that serious complications, such as maternal morbidity, can result from the procedure. They did note, however, the need for randomized prospective trials to determine the risks and benefits of episiotomy more conclusively.
Episiotomies are performed in more than 60% of vaginal deliveries in the United States. Episiotomy rates associated with midwifery management are significantly decreased, ranging from 5% to 26%.33,35 Goodlin47 described one technique utilized primarily by midwives to maintain an intact perineum and to prevent injury to the fetal head:
Another technique is to provide supportive direction to the mother to facilitate controlled deliveries. Recent studies have confirmed that midline episiotomies are associated with an increased risk for anal sphincter damage, especially in the event of operative deliveries.48,49 In response to studies advocating restrictive use of episiotomies (i.e., only to expedite the birth of a distressed infant) over liberal use (i.e., in an attempt to prevent perineal tearing), there appears to be evidence of declining overall rates of episiotomy use.34
There is no universal approach to the management of normal labor and delivery. Alternate management protocols that address the problem of labor dystocia should be considered as possible solutions to the high cesarean section rate. A common point of these alternate protocols is a more stringent criterion for the diagnosis of labor and a strong emphasis on providing supportive care. This minimizes the possibility of unnecessary interventions in early labor that could be the origin of iatrogenic dystocia. Any labor management protocol must maintain a reasonably low incidence of maternal and neonatal morbidity for it to be acceptable.
22. American College of Obstetricians and Gynecologists: Induction and Augmentation of Labor. Technical Bulletin Publication No. 157. Washington, DC, American College of Obstetricians and Gynecologists, 1991
23. Thorp JA, Boylan PC, Parisi VM, Heslin EP: Effects of high-dose oxytocin augmentation on umbilical cord blood gas values in primigravid women. Am J Obstet Gynecol 159: 670, 1988
35. Greulich B, Paine L, McClain C et al: Twelve years and more than 30,000 nurse-midwife attended births: Los Angeles County/ University of Southern California Women's Hospital Birth Center experience. J Nurse Midwifery 39: 185, 1994
38. Read J, Miller F, Paul R: Randomized trial of ambulation versus oxytocin for labor enhancement: A preliminary report. Am J Obstet Gynecol 139: 669, 1981