Continuing Education Activity

Labor is a process that is subdivided into 3 stages. The first stage starts when labor begins and ends with full cervical dilation and effacement. The second stage commences with complete cervical dilation and ends with the delivery of the fetus. The third stage initiates after the fetus is delivered and ends when the placenta is delivered. This activity outlines the stages of labor and its relevance to the interprofessional team in managing women in labor.

Objectives:

• Identify the three stages of labor.

• Evaluate potential complications that may arise during each stage of labor.

• Determine what therapies may be targeted at the different stages of labor to result in better patient outcomes.

• Communicate the importance of accurate communication between the interprofessional team members regarding the stages of labor, which will lead to improved patient outcomes.

Introduction

Labor is the process through which a fetus and placenta are delivered from the uterus through the vagina.[1] Human labor is divided into 3 stages. The first stage is further divided into 2 phases. Successful labor involves 3 factors: maternal efforts and uterine contractions, fetal characteristics, and pelvic anatomy.[1] This triad is called the passenger, power, and passage.[1] Clinicians typically use multiple modalities to monitor labor. Serial cervical examinations are used to determine cervical dilation, effacement, and fetal position, also known as the station. Fetal heart monitoring is employed nearly continuously to assess fetal well-being throughout labor. Cardiotocography is used to monitor the frequency and adequacy of contractions. Medical professionals use the information they obtain from monitoring and cervical exams to determine the patient's stage of labor and monitor labor progression.

Women often self-present to obstetrical triage with concern for the onset of labor. Common chief complaints include painful contractions, vaginal bleeding/bloody show, and fluid leakage from the vagina. It is up to the clinician to determine if the patient is in labor, defined as regular, clinically significant contractions with an objective change in cervical dilation or effacement.[1] When women arrive at the labor and delivery unit, vital signs, including temperature, heart rate, oxygen saturation, respiratory rate, and blood pressure, should be obtained and reviewed for abnormalities. The patient should be placed on continuous cardiotocographic monitoring to ensure fetal well-being. The patient's prenatal record, including obstetric, surgical, medical, laboratory, and imaging data, should be reviewed. Finally, a history of present illness, a review of systems, and a physical exam, including a sterile speculum exam, must be performed.

During the sterile speculum exam, clinicians look for signs of rupture of membranes, such as amniotic fluid pooling in the posterior vaginal canal. Suppose the clinician is unsure whether or not a rupture of membranes has occurred. In that case, additional testing such as pH testing, microscopic exams looking for ferning of the fluid, or laboratory testing of the fluid can be the next step.[2] Amniotic fluid has a pH of 7.0 to 7.5, which is more basic than normal vaginal pH. A sterile gloved exam should determine the degree of cervical dilation and effacement. The cervical dilation is measured by locating the external cervical os, spreading one's fingers in a ‘V’ shape, and estimating the distance in centimeters between the 2 fingers. Effacement is measured by estimating the percentage remaining of the length of the thinned cervix compared to the uneffaced cervix. During the cervical exam, confirmation of the presenting fetal part is also necessary. Bedside ultrasound can be employed to confirm the presentation and position of the fetal presenting part. Particular mention should be noted in the case of breech presentation due to its increased risks regarding fetal morbidity and mortality compared with the cephalic presenting fetus. 

Labor is a natural process, but it can be interrupted by complicating factors, which sometimes necessitate clinical intervention. Managing low-risk labor is a delicate balance between allowing the natural process to proceed and limiting potential complications.[3] During labor, cardiotocographic monitoring is often employed to monitor uterine contractions and fetal heart rate over time. Clinicians monitor fetal heart tracings to evaluate for any signs of fetal distress that would warrant intervention, as well as the adequacy or inadequacy of contractions. The mother's vital signs are taken regularly whenever concerns arise regarding a clinical status change. Laboratory testing often includes the hemoglobin, hematocrit, and platelet count and is sometimes repeated following delivery if significant blood loss occurs. Cervical exams are usually performed every 2 to 3 hours unless concerns arise and warrant more frequent exams. Frequent cervical exams are associated with a higher risk of infection, mainly if a rupture of membranes has occurred. Women should be allowed to ambulate freely and change positions if desired.[3] An intravenous catheter is typically inserted in case it is necessary to administer medications or fluids. Oral intake should not be withheld. Suppose the patient remains without food or drink for a prolonged period. In that case, intravenous fluids should be considered to help replace losses but should not be used continuously on all laboring patients.[3] Analgesia is offered in the form of intravenous opioids, inhaled nitrous oxide, and neuraxial analgesia in those who are appropriate candidates.[4] Amniotomy is considered on an as-needed basis for fetal scalp monitoring or labor augmentation, but its routine use should be discouraged.[3] Oxytocin may be initiated to augment contractions found to be inadequate.

The first stage of labor begins when labor starts and ends with full cervical dilation to 10 centimeters.[1] Labor often begins spontaneously or may be induced medically for various maternal or fetal indications.[5] Methods of inducing labor include cervical ripening with prostaglandins, membrane stripping, amniotomy, and intravenous oxytocin.[5] Although precisely determining when labor starts may be inexact, labor is generally defined as beginning when contractions become strong and regularly spaced at approximately 3 to 5 minutes apart.[1] Women may experience painful contractions throughout pregnancy that do not lead to cervical dilation or effacement, referred to as false labor. Thus, defining the onset of labor often relies on retrospective or subjective data. Friedman et al were some of the first to study labor progress and defined the beginning of labor as starting when women felt significant and regular contractions.[6] He graphed cervical dilation over time and determined that normal labor is sigmoidal. Based on the analysis of his labor graphs, he proposed that labor has 3 divisions. First, a preparatory stage is marked by slow cervical dilation, with large biochemical and structural changes. This is also known as the latent phase of the first stage of labor. Second, a much shorter and more rapid dilational phase is also known as the active phase of the first stage of labor. Third is the pelvic division phase, which occurs during the second labor stage.[1]

The first stage of labor is further subdivided into 2 phases, defined by the degree of cervical dilation. The latent phase is 0 to 6 cm, while the active phase commences from 6 cm to full cervical dilation. The presenting fetal part also begins the process of engagement into the pelvis during the first stage. Throughout the first stage of labor, serial cervical exams are done to determine the position of the fetus, cervical dilation, and cervical effacement. Cervical effacement refers to the cervical length in the anterior-posterior plane. When the cervix is completely thinned out, and no length is left, this is called 100 percent effacement.[1] The station of the fetus is defined relative to its position in the maternal pelvis. When the bony fetal presenting part is aligned with the maternal ischial spine, the fetus is 0 station. Proximal to the ischial spines are stations -1 centimeter to -5 centimeters, and distal to the ischial spines are +1 to +5 station.[1] The first stage of labor contains a latent phase and an active phase. During the latent phase, the cervix dilates slowly to approximately 6 centimeters. The latent phase is generally considerably longer and less predictable concerning the cervical change rate than observed in the active phase. A normal latent phase can last up to 20 hours and 14 hours in nulliparous and multiparous women, respectively, without being prolonged.[1] Sedation can increase the duration of the latent phase of labor.[7] The cervix changes rapidly and predictably in the active phase until it reaches 10 centimeters and cervical dilation and effacement are complete. Active labor with more rapid cervical dilation generally starts around 6 centimeters. During the active phase, the cervix typically dilates at 1.2 to 1.5 centimeters per hour. Multiparas, or women with a history of prior vaginal delivery, tend to demonstrate more rapid cervical dilation.[1] The absence of cervical change for greater than 4 hours in the presence of adequate contractions or 6 hours with inadequate contractions is considered the arrest of labor and may warrant clinical intervention.[7] 

The second stage of labor commences with complete cervical dilation to 10 centimeters and ends with the delivery of the neonate. Friedman also defined this as the pelvic division phase. After cervical dilation is complete, the fetus descends into the vaginal canal with or without maternal pushing efforts. The fetus passes through the birth canal via 7 movements known as the cardinal movements. These include engagement, descent, flexion, internal rotation, extension, external rotation, and expulsion.[1] In women who have delivered vaginally previously, whose bodies have acclimated to delivering a fetus, the second stage may only require a brief trial. In contrast, a longer duration may be required for a nulliparous female. In parturients without neuraxial anesthesia, the second stage of labor typically lasts less than 3 hours in nulliparous women and less than 2 hours in multiparous women. In women who receive neuraxial anesthesia, the second stage of labor typically lasts less than 4 hours in nulliparous women and less than 3 hours in multiparous women.[1] If the second stage of labor lasts longer than these parameters, the second stage is considered prolonged. Several elements may influence the duration of the second stage of labor, including fetal factors such as fetal size and position, maternal factors such as pelvis shape, the magnitude of expulsive efforts, comorbidities such as hypertension or diabetes, age, and history of previous deliveries.[8] 

The third stage of labor commences when the fetus is delivered and concludes with the delivery of the placenta. Separation of the placenta from the uterine interface is hallmarked by 3 cardinal signs, including a gush of blood at the vagina, lengthening of the umbilical cord, and a globular-shaped uterine fundus on palpation.[1] Spontaneous expulsion of the placenta typically takes between 5 to 30 minutes.[1] A delivery time of greater than 30 minutes is associated with a higher risk of postpartum hemorrhage and may be an indication for manual removal or other intervention.[1] Management of the third stage of labor involves placing traction on the umbilical cord with simultaneous fundal pressure to effect faster placental delivery. 

Function

The function of the stages of labor is to create a universal definition that medical professionals can use to communicate with each other about labor. The stages of labor can also help determine where the patient is on the labor spectrum. Clarifying the stages of labor has helped create guidelines that define normal and abnormal trends in labor. Clinical management also gears toward the various stages of labor. 

Issues of Concern

Complications may arise during any of the stages of labor to result in abnormal labor. During the first stage, women may experience the arrest of parturition, necessitating cesarian delivery, which may carry greater maternal or fetal risk. Second-stage complications include a variety of complications related to the trauma of the delivery process to either the fetus or the mother. The fetus can suffer acidemia, shoulder dystocia, bony fractures, nerve palsies, scalp hematomas, and anoxic brain injuries. Similarly, the mother can develop a host of traumatic complications ranging from uterine rupture, vaginal laceration, cervical laceration, uterine hemorrhage, amniotic fluid embolism, and death. The third stage of labor may encounter complications from hemorrhage, cord avulsion, retained placenta, or incomplete removal of the placenta.[5]

Clinical Significance

Defining the stages of labor with a specific beginning and end has allowed clinicians to study labor trends and create labor curves. For example, in the 1950s, Dr. Friedman created a graphical representation of the normal labor rate during latent and active labor using observed clinical data.[9] These, in turn, can be used to determine if a woman is progressing through labor as expected and help to identify abnormal labor. Friedman observed that labor typically has a sigmoidal shape when measured by cervical dilation. During the active phase of labor, cervical dilation occurs at a rate of 1 centimeter or more per hour. If dilation occurs much slower, the patient may be at risk for abnormal labor or arrest of labor.[10] 

If a woman is found not progressing through the first stage of labor as expected, this could lead to the diagnosis of the arrest of dilation or descent, which could result in cesarean delivery. The findings of Dr. Friedman have recently been challenged, and the current consensus is the normal latent phase of labor lasts longer than was previously observed.[8] The criteria for the stages of labor create a universal language that allows healthcare professionals to communicate with one another about patient care accurately. Also, specific interventions are tailored to particular labor stages to create better patient outcomes. For example, active management in the third stage of labor is carried out by placing immediate traction on the umbilical cord and administering intravenous oxytocin, which correlates with a lower risk of postpartum hemorrhage.[11] Clinicians continue to use the stages of labor to guide labor management and study labor patterns to improve patient care.

Enhancing Healthcare Team Outcomes

The stages of labor describe a complex physiologic process that starts when labor begins and ends with the delivery of the fetus and placenta. An interprofessional team usually monitors labor clinically with multiple modalities. Labor can proceed as typically expected with certain cardinal events and time parameters or encounter complications and delays, which may require identification and medical intervention. The role of the interprofessional team in monitoring and caring for women during labor is critically important in keeping women safe and improving outcomes during the labor process.

Medical professionals such as nurses, midwives, pharmacists, family physicians, anesthesiologists, and obstetricians/gynecologists may be involved in a woman’s labor process. Close communication is needed between these professionals to create an atmosphere of safety and patient-centered care. Midwives often manage labor and delivery and work closely with physicians when complications arise, requiring physician intervention, such as Caesarian section or operative delivery. Pharmacists ensure that patients receive the proper analgesics, tocolytics, and other medications needed during or following labor. Anesthesiologists and nurse anesthetists administer epidurals for analgesia and are available for general endotracheal anesthesia when necessary. Nurses monitor the patient’s vital signs, contractions, cervical exams, and pain scores, administer medications, recognize complications, and update the physician or midwife responsible for the patient. Each labor is unique, but an interprofessional approach prenatally and during labor can be used to improve patient outcomes and provide patient-centered care, as each provider class works collaboratively to ensure communication lines remain open between different disciplines on the health care team. A Canadian retrospective cohort study of 1238 women found that an interprofessional team approach to obstetrical care provided better patient outcomes by decreasing the rate of cesarian sections and length of hospital stays for women.[12]

Nursing, Allied Health, and Interprofessional Team Interventions

Nurses are intimately involved in monitoring and caring for laboring women. They administer and titrate medications during labor, such as oxytocin. They also monitor the vital signs, pain scores, and labor progression of women and fetuses closely and are responsible for recognizing and then notifying physicians and midwives when abnormalities arise.