10.3 Labor

Labor is the body’s natural process of childbirth. It typically lasts about 12 to 24 hours for a woman who has never given birth to a live baby (nulliparous) but is often shorter for a woman who has previously given birth once (primiparous) or more than once (multiparous).

Physiology of Labor

Labor begins with contractions of the uterus that move the fetus down into the maternal pelvis and cause the cervix to open, thin, and stretch in preparation for delivery. While the actual mechanisms that initiate labor have not yet been identified, it is theorized that the pregnant woman, fetus, and placenta each have a part in the process. Factors originating from the pregnant woman include uterine stretch from the growing fetus and amniotic fluid, as well as decreased progesterone levels and increased estrogen levels. As the progesterone level drops, the uterus becomes ready to respond to oxytocin, which initiates uterine contractions in an intermittent pattern every few minutes until birth and through the postpartum period to prevent hemorrhage. Placental release of corticotropin-releasing hormone (CRH) also peaks when the pregnancy is full term. CRH is believed to trigger the fetal brain to stimulate lung maturity and initiate uterine contractions through increasing cortisol levels and support of elevated levels of estrogen.^[1],[2],[3]

Early Signs and Symptoms of Impending Labor

Several signs and symptoms indicate that labor may be beginning soon. It is important to remember that each pregnancy is different, and some pregnant people may experience all of these signs, while others experience none. Additionally, these signs of impending labor can occur hours, days, or weeks before the onset of true labor. Early signs and symptoms of impending labor including lightening, cervical ripening, Braxton-Hicks contractions, bloody show, nesting, and rupture of membranes^[4]:

• Lightening: Lightening refers to the fetal head dropping into the maternal pelvis, also known as engagement of the fetal head. The pregnant client may feel it is easier to breathe when lightening occurs, although there is often more pressure on the bladder as the fetus moves away from the diaphragm and toward the bladder. Lightening may occur a few weeks prior to the start of labor.^[5]
• Cervical ripening: The cervix is usually thick and firm throughout pregnancy. At the end of pregnancy, cervical ripening occurs where the cervix becomes softer and thinner. This is also referred to as effacement. Ripening of the cervix may occur several weeks before labor begins.^[6]
• Braxton-Hicks contractions: Braxton-Hicks contractions, also known as false labor contractions, occur in the last few months of pregnancy. These contractions are mild, irregular (i.e., without a pattern), do not get more intense or more frequent, and do not cause cervical changes. They often go away when the woman walks, rests, or changes position. However, true contractions associated with the onset of labor are regular, get closer together, get stronger, and continue even with position changes, rest, or movement. Nurses teach pregnant clients to call their health care provider if their contractions last at least 30 to 70 seconds, occur at regular intervals about five to seven minutes apart, and don’t go away even if they lie down and rest.^[7]
• Bloody show: During pregnancy there is mucus in the cervical opening. When the cervix begins to soften and thin during the end of pregnancy, this mucus is released through the vagina. The woman may notice a thick, bloody, mucus discharge commonly called bloody show. It is usually pink, brown, or reddish in color but is not bright red bleeding. Nurses teach women that bright red bleeding or trickling blood is not a normal finding and may indicate a placental complication that warrants immediate notification of the health care provider.^[8]
• Nesting: In the third trimester of pregnancy, fatigue is a common symptom. However, a sudden burst of energy can be a sign of impending labor. In some cultures, this energy increase is referred to as nesting because women often use the extra energy to prepare for the arrival of the baby. Nurses encourage pregnant clients to stay hydrated and well-nourished if this burst of energy occurs and to rest between activities to promote wellness during the upcoming labor.^[9]
• Rupture of membranes: Some women experience spontaneous rupture of the amniotic sac prior to the onset of labor, referred to as rupture of membranes (ROM). Nurses teach pregnant clients that if rupture of membranes occur, they should note the time, color, amount, and odor of the fluid and immediately report the event to their health care provider. Amniotic fluid has no odor and is clear in color. Nurses visually inspect sanitary napkins or other absorbent materials brought in by the pregnant client who may have experienced spontaneous rupture of membranes prior to the onset of labor. They may use commercially available diagnostic tests to test for amniotic fluid such as Amnisure or ROM Plus. Nurses may also use nitrazine paper to determine the pH of the fluid and/or perform a microscopic examination of the fluid that will reveal a distinct ferning pattern as it dries on the slide if it is amniotic fluid.1 See an image of ferning of amniotic fluid on a slide in Figure 10.1.^[10]

Stages of Labor

When true labor begins, it progresses through a three-stage process that can follow a typical pattern or deviate from normal. The American College of Obstetricians and Gynecologists (ACOG) defines the first stage of labor as the interval between the onset of labor and 10 centimeters (cm) cervical dilation. The first stage is further divided into two phases called latent and active. The latent phase of labor is characterized by gradual cervical dilation that starts on perception of regular uterine contractions and ends when rapid cervical change initiates. This phase of rapid cervical change is termed the active phase of labor and continues until complete cervical dilation. The second stage of labor commences at 10 cm cervical dilation and ends on delivery of the neonate. The third stage of labor is the period between delivery of the neonate and delivery of the placenta.^[11] See Figure 10.2^[12] for an illustration of the three stages of labor.

After the placenta is delivered, the initial one to four hours postpartum are sometimes referred to as the fourth stage of labor.

Nurses monitor labor progression and notice cues indicating that labor is deviating from normal. Nursing interventions are implemented for deviations from normal labor, and the health care provider is notified for additional interventions that may be needed that are outside the scope of nursing. To know when to intervene, nurses must understand normal progression through the three stages of labor.^[13]

First Stage of Labor

The first stage of labor begins with uterine contractions and progresses through latent and active phases.

The latent phase of the first stage of labor begins with uterine contractions lasting 30-45 seconds that occur every five to ten minutes. These contractions typically start causing cervical changes within four hours. During this phase, the mother is typically excited and talkative. The latent phase ends when cervical dilation progresses to six cm and takes an average of 10-14 hours for a woman who is nulliparous but may be shortened for a woman who is primiparous or multiparous. It is often best for the mother to be in the comfort of her own home until contractions become five minutes or less apart. The threshold for coming to the hospital prior to this may be lowered depending on the travel distance to the hospital and if any risk factors are present. Nurses teach clients about actions they can do at home to help the labor progress7,^[14]:

• Take a walk near home
• Change positions frequently
• Use breathing and relaxation techniques
• Take a warm shower or soak in a warm tub (if amniotic membranes have not yet ruptured)
• Rest
• Drink plenty of fluids and eat a light meal
• Get packed and ready for the hospital stay

The active phase of the first stage of labor begins when cervical dilation is at six cm and ends when it is fully dilated at 10 cm. During the active phase, contractions last 40-90 seconds and occur every two to five minutes. Contractions are typically moderate to strong in intensity and may require assistance from the client’s partner or support person to help them cope with the pain. The duration of this phase varies across individuals and may last minutes to hours. Other signs that a client is reaching the active phase of labor can include nausea and vomiting, becoming more internally focused, being unable to answer questions or converse during contractions, and feeling vaginal and rectal pressure. Spontaneous rupture of membranes may occur during the active phase.^{[15],[16],[17]}

Clients are encouraged to frequently reposition during the active phase to promote comfort and cervical dilation. See Figure 10.3^[18] for common positions during active labor such as hands and knees, left and right side-lying position, sitting on a birth ball, shower hydrotherapy in an upright position, standing in a supported position, squatting with a chair, or sitting backwards on a chair with pressure applied to the sacrum.^[19],[20]

See Table 10.3a for an overview of latent and active phases of the first stage of labor.

Table 10.3a. Latent and Active Phases of the First Stage of Labor^[21],^[22]

Fetal heart monitoring is used to assess fetal well-being throughout labor and is further discussed in the “Fetal Heart Rate Monitoring” section.

Pain during labor is influenced by maternal position, fetal position, anxiety, fear, stress, and social support. Nurses are integral in providing emotional support and comfort measures during the labor experience. Pain management is further discussed in the “Pain Management During Labor and Delivery” section.

Labor progress is continually assessed by the nurse and health care provider. If the duration of the first stage of labor exceeds established averages, the laboring client may be diagnosed with dystocia (lack of progress during labor), and medical interventions such as labor augmentation may be implemented. Read more about dystocia and labor augmentation under the “Complications Associated With Labor” section.

Second Stage

The second stage of labor begins when the cervix is completely dilated, 100% effaced, and maternal pushing efforts begin.^[23] See Table 10.3b for an overview of characteristics of the second stage of labor.

Table 10.3b. Characteristics of the Second Stage of Labor^[24]

If pushing efforts exceed three hours in a primiparous or multiparous client, or four hours in a nulliparous client, there is an increased risk for complications, and medical interventions such as operative vaginal delivery or cesarean birth may be performed.^[25] Read more about operative vaginal delivery and cesarean birth under the “Complications and Medical Interventions Associated With the Second Stage of Labor” section.

Mechanisms of Birth

During the second stage of labor, the fetus engages into the maternal pelvic inlet and undergoes a specific series of movements to navigate the pelvis. These movements are called the mechanisms of birth, or cardinal mechanisms, and their purpose is to allow the fetus to adjust its position and size in relation to the mother’s pelvis in preparation for delivery. See Figure 10.4^[26] for an illustration of the mechanisms of birth that shows 1) Before engagement of the fetal head, 2) Engagement of the fetal head, 3) Descent and rotation of the fetus, 4) Complete rotation of the fetus and initial extension of the neck, 5) Complete extension of the neck, 6) Restitution, 7) Anterior shoulder delivery, and 8) Posterior shoulder delivery.

The mechanisms of birth begin when the fetal head engages in the pelvic inlet (e.g., the top opening of the pelvis) and end when the fetal head and body exit from the pelvic outlet. When crowning of the fetal head is noted at the pelvic outlet, preparations begin for imminent birth even though it may take some time for delivery as the mother makes slow, controlled expulsive efforts. The health care provider should be present at this point with hands poised to assist. After the fetal head is pushed out of the vagina, restitution of the fetal shoulders occurs, which means the fetal shoulders turn to the left or right oblique diameter of the pelvis to allow for easier passage under the maternal pubic arch. Restitution is followed by external rotation of the fetal head with the fetal face directed toward the mother’s left or right thigh. After external rotation of the fetal head, the fetal shoulders are delivered by the health care provider using gentle downward traction on the anterior shoulder followed by upward traction on the posterior shoulder as the newborn is lifted toward the mother’s abdomen. After the fetal shoulders are delivered, the remainder of the body should follow smoothly.^[27]

During mechanisms of birth, the fetal shoulder may get stuck under the maternal symphysis pubis, called shoulder dystocia. Read more about potential complications during the second stage of labor under the “Complications and Medical Interventions Associated With the Second Stage of Labor” section.

Third Stage

The third stage of labor begins after the newborn is delivered and ends when the placenta is delivered. The average time frame for the third stage is between 5 and 30 minutes. Placental delivery should occur within 30 minutes of the time of birth to reduce the risk for hemorrhage. Signs and symptoms that the placenta has detached from the uterus and placental delivery is imminent include cramping, lengthening of the umbilical cord, change in the shape of the uterus as the placenta detaches from the uterus and moves into the vaginal canal, and increased vaginal bleeding. Nurses can help facilitate the birth of the placenta by encouraging the newborn to latch to the mother’s breast and stay skin-to-skin to increase physiologic maternal oxytocin levels.^[28] See Table 10.3c for an overview of the characteristics of the third stage of labor.

Table 10.3c. Characteristics of Third Stage of Labor

After the placenta is delivered, the initial one to four hours after birth are often referred to as the fourth stage of labor. This stage requires in-depth nursing care and monitoring for the mother and the newborn to identify and prevent complications. The nurse frequently assesses vital signs, vaginal bleeding, and fundal height and tone. The uterus should be firmly contracted with lochia rubra discharge. Lochia rubra is a dark or bright red discharge that is similar to a heavy period and may contain small blood clots. The nurse assesses for signs of postpartum hemorrhage that include hypotension, tachycardia, excessive vaginal bleeding, and a boggy/noncontracting uterus. Postpartum hemorrhage is a life-threatening concern that requires emergency intervention.1 Read more about postpartum hemorrhage in the “Complications and Medical Interventions Associated With the Third Stage of Labor” section.