Labor is defined as uterine contractions with a frequency and intensity strong enough to cause cervical dilation, cervical effacement, and ultimately descent of the fetal head into the maternal pelvis. From the Latin ob and stare is derived the term obstetrics, which means “to stand by.” Thus as obstetricians we are standing by the expectation and the hope, the contractions and the pain, and ultimately the descent of the fetal head into the maternal pelvis—waiting for the birth of new life.

The physiology of parturition is an orchestrated event involving many players—the myometrium, the decidua, and the uterine cervix. Throughout pregnancy, true labor is held in check by inhibitors such as progesterone, prostaglandin I-2, relaxin, and nitrous oxide. As the uterus readies for labor over the course of days and weeks, the increased expression of prostaglandin and oxytocin receptors is upregulated, in addition to an increase in myometrial gap junction formation. Following the onset of early labor, prostaglandins E2/F2-alpha, estrogen, and oxytocin coordinate to stimulate the myometrium, providing regular, rhythmic uterine contractions. Recent studies have posited that the surfactant molecule in the lungs of the fetus may play a role in parturition.¹ The pear shape of the uterus, as well as the gynecoid shape of the maternal pelvic bones, positions the fetus in the vertex presentation in nearly 97% of deliveries. The mechanical steps of the fetus in its passage through the birth canal are engagement, descent, flexion, internal rotation (most commonly, this is where the fetus rotates to the occiput-anterior position), extension, external rotation, and expulsion (Fig. 37-1). Station of the fetal head refers to where the biparietal diameter is in relation to the ischial spines of the maternal pelvis. Engagement of the fetal head is confirmed when the biparietal diameter of the vertex is at or past the level of the pelvic inlet. While engagement is an essential element of the cardinal movements, it can, and often does, happen before labor starts.

In 2015, nearly 4 million women gave birth in the United States, and 99% of these births were in a hospital.² As obstetrics and gynecology (OB/GYN) hospitalists, we oversee and manage many of these births, and our profession has contributed to an increase in the amount of evidence-based medicine that is brought to labor and delivery (L&D): how best to care for women in labor. While many private practices and hospitals employ certified nurse midwives (CNMs) to provide low-risk obstetric care in the hospital, a recent review of six trials of 16,500 low-risk women found that CNM-led L&D management was associated with a similar number of incidences of cesarean delivery and neonatal mortality¹ as to those led by obstetricians. We know that women in pregnancy appreciate having choices about their labor management. Increasing numbers of women elect to deliver outside the hospital setting,³ despite recent evidence showing increased neonatal mortality at planned home births.⁴ A goal for many hospitals is to provide inpatient obstetric services that offer more options for pain management and support during labor, while at the same time employing the best evidence-based practices.

Most women present to their outpatient clinic or the hospital OB triage unit with complaints of painful, regular contractions; and most women at this point are in the first stage of labor, defined as the onset of contractions, progressing to complete cervical dilation. OB/GYN hospitalists are often the first line of care for women entering OB triage, the Obstetric Emergency Department (OBED), or hospital Emergency Department (ED). They are, therefore, required to understand the Emergency Medical Treatment and Active Labor Act (EMTALA) and how it affects care in the hospital setting; transfers between hospitals; the Medical Screening Exam; and many other legal and practical considerations in the care of pregnant women.

While Braxton-Hicks contractions may originate in a variety of locations in the uterus, true labor is characterized by regular, organized muscular contractions originating in the fundus and traveling down toward the cervix. The job of anyone evaluating a woman for labor admission is to determine: Is this true or false labor? Painful contractions alone are not sufficient to diagnose labor; dilation and effacement must be present. There is an art to medicine—the cervical exam is a perfect case in point.

Effacement of the cervix begins when increasing number of gap junctions form, as well as upregulation of locally occurring PGE₂, which relaxes cervical smooth muscle and accelerates collagen breakdown, causing an upregulation of hyaluronic acid, thus increasing water content and decreasing collagen, which in turn causes breakdown and “softening” of the cervix.

There is much controversy as to when active labor actually begins. For some, the threshold is 6 cm. The first stage of labor is differentiated into the latent and active phases. The latent phase describes a period of slow cervical change, between 0 and 6 cm dilation. The active phase describes a more rapid cervical change, from 6 cm to complete dilation. Many use the term inflection point to describe the point at which the labor moves from the latent into the active phase. Delaying admission until a cervical dilation of at least 4 to 6 cm is reached, alongside regular and painful contractions, results in a higher rate of vaginal delivery. A recent study found that early labor assessment and confirmation of the active phase resulted in decreases in the duration of labor, use of epidurals, and oxytocin administration (Fig. 37-2).⁵ In addition, effacement plays a central role in correctly diagnosing labor. A recent study found that the more the cervix is effaced, the faster dilation occurs (Fig. 37-3).⁶

A new simplified Bishop score uses effacement, dilation, and station (excluding consistency and position).⁷ This simplified version predicted vaginal delivery with the same accuracy as the model from 1972, and it requires less interpretation and easier scoring. Standardizing the Bishop score, especially for induction of labor (IOL), may help to decrease admissions for women who have no medical indication for induction and thus are not favorable for a vaginal delivery.

Most women admitted for active labor are between 4 and 6 cm. A study performed in Washington found that women admitted at <4 cm were at increased risk of oxytocin administration and cesarean delivery.⁸ Admission examination includes a review of the prenatal record, obstetrical, medical and surgical history, medications and allergies, a review of social history and depression screening, review of systems, and an analysis of prenatal laboratory data, including GBS status (Table 37-1). A complete physical exam should pay special attention to blood pressure and heart rate, fetal status and uterine contractions. The examiner should note whether fetal membranes are intact or ruptured, whether there is any bleeding noted on vaginal exam, confirmation of fetal vertex, the station, as well as the lie, presentation and position of the fetus. Lastly, an estimated fetal weight (EFW) is essential. Interestingly, a recent study demonstrated that clinical exam (Leopold’s) for EFW at term had a better estimation than ultrasonographic estimation.⁹

Recent studies have shown no value in routine administration of enemas for labor, and negative implications for shaving the perineum prior to delivery. There is no evidence to support vaginal or vulvar cleaning with chlorhexidine or betadine prior to delivery either. Data is mixed on placement of warm compresses preventing perineal trauma, but there is no harm in doing so. Emerging data on the intake of fluids and solids in labor is changing practice. In 2009, American Congress of Obstetrician and Gynecologist’s (ACOG’s) Committee Opinion stated there was insufficient evidence to recommend fasting in labor; Cochrane and the World Health Organization (WHO) followed suit and both state there is no justification for oral restriction in labor. We know dehydration adversely affects women in labor—just as athletes needs fluids and dextrose to exercise, so do women in labor. Fluids, whether oral or IV, are definitely recommended for women in the birth process. IV fluids at a rate of 250 mL/hr are associated with decrease length of first stage of labor (71 minutes)¹⁰ and may help to decrease cesarean delivery risks as well. A recent study comparing 5% dextrose in normal saline during labor with normal saline alone found a 76 minute reduction in the total length of labor in the dextrose group.¹¹ Particulate containing fluids should be avoided, but clear liquids of the patient’s choice often increase the satisfaction of the parturient without increasing any risks to her labor.

The Committee on Obstetric Practice of the American College of Obstetricians and Gynecologists (ACOG) released an updated opinion in 2011 that affirmed the importance of antibiotic administration for GBS-screened positive women. Ideally, a minimum of 4 hours of antibiotics is achieved prior to delivery, with penicillin remaining the first-line agent and clindamycin and vancomycin indicated for those women both with and without sensitivity to clindamycin and erythromycin, respectively. See Chapter 26 for more information about GBS prophylaxis.

A recent review from 2013 found that walking and upright positions during the first stage of labor reduced the duration of labor (by 1 hour, 22 minutes), the need for epidural, and the risk of cesarean delivery.¹² Other reviews suggest that women should be allowed to choose when and if to ambulate in the first stage of labor. This was supported by a recent ACOG Committee Opinion regarding intervention during L&D: “Labor management may be individualized to include techniques such as intermittent auscultation and nonpharmacologic methods of pain relief.”¹³ During labor, experts suggest that alternating maternal positions (possibly combined with walking) is best, and that there is no one ideal position for labor. Having said that, upright or lateral positions are associated with fewer abnormal fetal heart rate (FHR) tracing patterns.¹⁴

ACOG states that water immersion in the first stage of labor may be associated with shortened labor, but cautions against birthing in water, given a lack of data and possible risk of infection.¹⁵ There is no evidence of any fetal distress or harm from water immersion in the first stage of labor. However, in the second stage, there have been numerous reports of severe neonatal complications, and even reported deaths, due to neonatal infections. ACOG states, “Therefore, until such data are available, it is the recommendation of the College that birth occur on land, not in water.”

During the first stage of labor, pain signals enter through T10-12 and L1, with possible referral to the back, anterior abdominal wall, groin, and hip. During this stage, women who desire pain management typically are offered neuraxial or systemic anesthesia. Neuraxial anesthesia includes epidural, spinal, or spinal/epidural, and approximately 70% of women opt for this method of pain relief in labor. Whereas in the past, a minimum requirement of cervical dilation was necessary, recent studies demonstrate that the timing of neuraxial anesthesia does not affect the likelihood of arrest disorders of labor. Other options for pain management include nitrous oxide, fentanyl, morphine, nalbuphine, and butorphanol. Where health care personnel on L&D in the past asked the question, “How much pain are you experiencing on a scale of 1 to 10?”, the Joint Commission now suggests an alternative: “On a scale of 1 to 10, how well are you coping with your labor?”¹⁶

Continuous support during labor has been shown in recent studies to play a key role in women’s experience of the birth of children as well as their need for operative delivery and consumption of pain medication.¹⁷ Randomized trials have found that use of doulas results in shortened labors, decreased anesthesia use, and heightened satisfaction with labor.¹⁸ A recent ACOG Committee Opinion suggests that healthcare delivery systems may want to incorporate these types of support systems and personnel into the L&D care environment as a way to improve outcomes and provide emotional support and personalized care.

Other nonpharmacologic pain techniques include water immersion, acupuncture/acupressure, aromatherapy, audio-analgesia, breathing and relaxation, hypnobirthing, meditation and mindfulness techniques, and massage. Many hospitals have incorporated these and other amenities as a way to increase the comfort and satisfaction of the mother, while not compromising the safety of the mother or fetus. See Chapter 42 for further information about pain management in the laboring patient.

Historically, so-called normal labor, on average, was calculated at 1.2 cm/hr for nulliparous women and 1.5 cm/hr for multiparous. These rates were based on studies performed by Emanuel Friedman in the 1950s. Women’s diet, nutrition, exercise, incidence of diabetes, and obstetric anesthesia has changed since then. Zhang and colleagues examined the labor patterns of 62,415 women with spontaneous labor; his data demonstrates a longer latent phase of labor and a slower rate of change in active labor;¹⁹ this finding is supported by other researchers as well.²⁰ Conditions associated with slower labors include diabetes, chorioamnionitis, preeclampsia, large for gestational age infants, increased body mass index (BMI), maternal height, and induction. Zhang’s research points to a slower second stage of labor as well.²¹ The takeaway from this research is that each labor is individualized, that labors are slower than originally thought, and that practitioners, in order to avoid the diagnosis of arrest of labor too soon, should have more patience in labor.

The definition of active management of labor differs across geography and institution and cultures. Components include oxytocin administration and artificial rupture of membranes (AROM).

OXYTOCIN REGIMENS

Many oxytocin regimens are available. A common approach is to start at 0.5 to 2 mU/min and increase by 1 to 2 mU/min every 30 minutes until an adequate contraction pattern is established. A review in 2010 examined the efficacy of high-dose vs. low-dose oxytocin administration. “Low-dose” was defined as any dosing between 1 and 4 mU/min, with increases of 1 to 2 mU/min every 30 to 40 minutes. “High-dose” was ≥4 mU/min up to 7 mU/min, with short, incremental time intervals. Researchers examined 10 trials and concluded that high-dose oxytocin was associated with “moderate reduction in the rate of cesarean section, and a small increase in the rate of spontaneous vaginal delivery and shortened labor.”²² However, high-dose oxytocin was also associated with tachysystole, though no adverse maternal or neonatal outcomes were noted.

A review of nine randomized controlled trials (RCTs) found a similar outcome in examining IOL. When poor-quality trials were removed from the analysis, the time from induction to delivery was shortened, the likelihood of cesarean delivery was unchanged, and women in high-dose groups had higher rates of uterine tachysystole, with no adverse effects on mother or baby. Researchers concluded that there is insufficient evidence to recommend high-dose over low-dose regimens for IOL.²³ Finally, while a maximum high-dose of oxytocin has not been stated, for physiologic reasons (namely risk of hyponatremia secondary to excessive retention of water due to oxytocin’s molecular resemblance to antidiuretic hormone), most hospitals do not administer rates at >40 mU/min and many have caps at 20 or 30 mU/min.

AMNIOTOMY

A review of 15 randomized trials demonstrated that routine amniotomy has not been shown to offer any benefit (nor shortening of labor) and leads to an increase in chorioamnionitis, cesarean delivery, and potential for cord prolapse. Amniotomy can be helpful in conjunction with oxytocin administration in women undergoing IOL, and it is helpful when attempting to decompress a uterus with polyhydramnios—in a controlled and measured fashion. While women with hepatitis B, C, and/or HIV should not undergo routine amniotomy, those who are GBS positive are unaffected. In a review from 2013, researchers found that amniotomy alone did not shorten the duration of labor or decrease the likelihood of cesarean delivery.²⁴

ACOG has established guidelines for complications of pregnancy that warrant continuous electronic FHR monitoring. According to the organization, continuous or intermittent monitoring is acceptable in an uncomplicated patient, but conditions such as preeclampsia, intrauterine growth restriction (IUGR), type 1 diabetes, and other high-risk conditions should be monitored closely.²⁵ ACOG also recommends review of low-risk pregnancies every 30 minutes in the first stage of labor, and every 15 minutes in the second stage. The National Institute for Health and Care Excellence recommends continuous electronic fetal monitoring (EFM) for conditions such as chorioamnionitis, severe hypertension, oxytocin administration, meconium fluid, and vaginal bleeding.²⁶ While ACOG and other societies acknowledge that continuous EFM does not predict the likelihood of cerebral palsy, there is still the expectation within the public and the courts that all measures to predict neonatal outcomes should be used.

In 2008, ACOG, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the Society for Maternal-Fetal Medicine (SMFM) updated the EFM nomenclature and standardized the terminology used by healthcare personnel when describing fetal status based on EFM. Many hospitals and hospital systems require continuing medical education (CME) for delivering physicians, CNMs, and registered nurses (RNs) on a routine basis to ensure standardization of this nomenclature. OB/GYN hospitalists also play a role as the in-house attending who can, at a moment’s notice, assist a fellow physician or an RN in the interpretation of a fetal tracing, thereby, ideally, diminishing time from decision to incision if a Category III tracing is encountered, for instance.

Physician or CNM documentation of labor progress should include evaluation of the FHR (baseline, variability, presence or absence of accelerations, decelerations of type and severity), uterine contraction pattern, vital signs, and, if warranted, a cervical assessment. Recent studies have shown that limiting vaginal examinations of the cervix decreases the risk for chorioamnionitis. The common practice would be to examine the cervix at admission, when pain medicine is requested, when the patient feels the urge to push, and if any abnormal FHR tracing is noted. Some practitioners examine the cervix more frequently, but frequent exams, when ruptured, can increase the risk of infection as well as interventions. Patience can be a virtue on L&D. See Chapter 27 for further information about FHR monitoring.

Multiple studies have shown that warm compresses²⁷ and massage of the perineum in the second stage of labor has shown some benefit in the reduction of third- and fourth-degree lacerations.²⁸ Women should be given options and made aware of techniques that may limit damage to the perineum during labor.