Normal Labor: Physiology, Evaluation, and Management

Etiology

Labor is thought to be triggered by the activation of the decidua and fetal membranes, which may result from intrauterine inflammation, maternal vascular malperfusion of the placenta, uterine overdistension, maternal or fetal stress, or a breakdown of maternal-fetal tolerance.[2] After 37 weeks of estimated gestational age, membrane activation occurs as a normal physiologic process.

At term, membrane cells appear to increase the production of inflammatory proteins that help initiate labor.[3] A 2024 study found that human fetal membranes secrete a chemoattractant that stimulates leukocyte migration into the membranes approximately 1 to 2 weeks before delivery, leading to their activation.[4] These leukocytes then trigger the release of cytokines and prostaglandins, which promote structural changes in cervical collagen and glycosaminoglycans. For example, interleukin 1β and tumor necrosis factor stimulate matrix metalloproteinases within the fetal membranes, leading to degradation of the extracellular matrix in the cervix and membranes, which facilitates cervical dilation and membrane rupture.[5] Additionally, increased levels of chemokines and cytokines in maternal serum appear to be associated with the onset of labor.

Epidemiology

A large cohort study from London involving over 122,000 nulliparous women with singleton gestations and spontaneous labor found that the median gestational age at delivery was 39 weeks in Black and Asian women and 40 weeks in white European women.[6] This same study found that 8% of Black women, 7% of Asian women, and 5% of European women delivered before 37 weeks estimated gestational age.

Pathophysiology

Components of Labor: The 3 P's

Successful labor depends on the interaction of 3 key factors: uterine contractions and maternal efforts, fetal characteristics (eg, size, position, presentation, anatomy, and number of fetuses), and maternal pelvic anatomy (eg, the maximum diameters of the bony pelvis). These factors are commonly referred to as "power," "passenger," and "passage," respectively. Dysfunctional labor occurs when uterine power is insufficient to move the passenger through the passage. The adequacy of the passage should be assessed upon admission, while the power and passenger should be monitored at regular intervals throughout labor. 

The Cardinal Movements of Labor

During labor, the fetus must navigate the maternal bony pelvis. The obstetric conjugate, the smallest fixed distance through the pelvic inlet, measures approximately 11.5 to 12 cm in the average gynecoid pelvis. The transverse diameter of the maternal pelvis is slightly larger, averaging approximately 13 cm.[7] The largest diameters of the fetal head align in the anterior-posterior plane, whereas the widest part of the fetal shoulders is in the transverse plane. This anatomical relationship explains why the fetus rotates while passing through the maternal pelvis—this rotation optimizes alignment between the widest fetal dimensions and the larger transverse diameter of the maternal pelvis, facilitating passage through the true pelvis. These rotations, known as the cardinal movements of labor, are essential for a successful delivery.

Before true labor begins, the fetal head often engages with the bony pelvis, causing its biparietal diameter to descend below the plane of the pelvic inlet. Contact with the bony pelvis forces the fetal head into a flexed position, presenting its smallest diameter to the pelvic inlet.

The fetal head typically enters the pelvic inlet in a transverse position, with the fetus facing one of the maternal sides. This alignment allows the largest diameter of the fetal head to match the widest part of the pelvis. As the head descends through the true pelvis, the fetus internally rotates to an anterior-posterior position, facing either the maternal abdomen or back. This rotation aligns the bisacromial (shoulder) diameter with the transverse diameter of the maternal pelvis.

The fetal head then extends as it passes beneath the pubic bone, leading to the delivery of the head. The head then restitutes and externally rotates, realigning with the shoulders so that the fetus is "facing forward" relative to its body. This final adjustment returns the body to a transverse position as the rest of the fetus is expelled from the birth canal.

To summarize, the following are the cardinal movements of labor:

1. Engagement
2. Flexion
3. Descent
4. Internal Rotation
5. Extension
6. External rotation (also called restitution)
7. Expulsion

Stages of Labor

The stages of labor have been clearly defined to establish universal terminology, enabling medical professionals to communicate effectively. These definitions have facilitated the development of guidelines that distinguish normal from abnormal labor patterns and allow professional organizations to recommend stage-specific interventions.

In the 1950s, Friedman et al were among the first to study normal labor progression, defining the onset of labor as the point when women experienced significant and regular contractions.[8] By graphing cervical dilation over time, Friedman observed that labor follows a sigmoidal curve.[9][10] Based on this analysis, he proposed 3 divisions of labor.

The 1st is the preparatory stage, characterized by slow cervical dilation and substantial biochemical and structural changes. This phase is now known as the latent phase of the 1st stage of labor. Next is the dilational phase, a much shorter period of rapid cervical dilation known as the active phase of the 1st stage. Following this period, the fetus begins to descend through the true pelvis, a process that occurs most significantly during the 2nd stage of labor.

More recently, Zhang et al updated Friedman's labor curves using data from 2005 to 2007.[11] Zhang's team found that modern labor often progressed more slowly than previously described by Friedman, particularly before parturients reach 6 cm of dilation. The group also observed that the rate of cervical dilation typically increased more gradually rather than showing the abrupt transition from the latent to active phases noted by Friedman.

Like Friedman, Zhang identified a phase of rapid dilation. However, for both nulliparous and parous parturients, this phase did not consistently begin until they reached 6 cm of dilation. Before reaching 6 cm, both nulliparous and parous parturients dilated at similar rates. After 6 cm, parous parturients dilated faster than nulliparous ones.

These updated curves are useful for determining whether a parturient is progressing through labor as expected and for guiding intervention decisions. For example, during the active phase of labor, cervical dilation typically occurs at a rate of 1 to 2 cm per hr. If dilation is slower than the 95th percentile of parturients in normal labor, the individual may be experiencing protracted labor and could be at risk for arrest of labor.[12]

Before the onset of true labor

Pregnant individuals may experience painful contractions throughout pregnancy that do not lead to cervical dilation or effacement. This occurrence is referred to as "false labor," also known as Braxton Hicks contractions. Identifying the onset of labor often relies on retrospective or subjective data. Before true labor begins, pregnant individuals may also experience "lightening," a change in the shape of the abdomen accompanied by a sensation that the baby is lighter due to fetal descent into the pelvis. This event may be accompanied by increased leg edema and urinary frequency. Additionally, "bloody show" and the loss of the mucus plug can occur as the cervix begins to efface, often before the onset of true labor, especially in nulliparous patients.

First stage of labor

The 1st stage of labor begins with the onset of regular uterine contractions that cause cervical change and ends with full cervical dilation of 10 cm. Labor often begins spontaneously, although it may also be medically induced for various maternal or fetal indications.[13] The 1st stage of labor is subdivided into 2 phases: latent and active. These phases are defined by the degree of cervical dilation.

The latent phase refers to the period of slow cervical dilation, typically from 0 cm to 4 cm or 6 cm. This phase is generally much longer and less predictable than the active phase. According to Friedman's classic curve, the latent phase can last up to 20 hr in nulliparous women and up to 14 hr in multiparous women. Sedation may increase the duration of this phase.

The American College of Obstetricians and Gynecologists (ACOG) supports using Zhang's curve data and recommends, in their Clinical Practice Guideline #8, that a prolonged latent phase be defined as lasting more than 16 hr, regardless of parity. However, most individuals with a prolonged latent phase will either stop contracting or progress to the active phase with oxytocin or amniotomy. For this reason, cesarean birth is not appropriate for a prolonged latent phase in individuals with spontaneous contractions.

The latent phase may be longer for parturients undergoing induction of labor. When maternal and fetal status remains reassuring, the ACOG recommends allowing 12 to 18 hr of oxytocin administration after rupture of membranes before diagnosing a failed induction of labor.

The active phase comprises the more rapid rate of cervical dilation that occurs from 6 cm to full dilation. During this phase, cervical dilation typically follows a more predictable rate. Around 95% of parturients will dilate between 1 and 2 cm per hr in the active phase, with multiparous individuals dilating faster than nulliparous individuals. Amniotomy may be considered if a delay in the active phase is suspected, eg, less than 2 cm of dilation is achieved in 4 hr, according to U.K. guidelines. If no progress follows the amniotomy, oxytocin may be administered to increase the strength and frequency of contractions.

Active phase arrest of labor is diagnosed in parturients with ruptured membranes who are at least 6 cm dilated and have no cervical change for at least 4 hr with adequate contractions or at least 6 hr with inadequate contractions despite oxytocin administration.[14] Adequate contractions are defined as achieving at least 200 Montevideo units (MVUs), measured by an intrauterine pressure catheter (IUPC).

Second stage of labor

The 2nd stage of labor begins when the parturient reaches complete cervical dilation of 10 cm and ends with the delivery of the neonate. Friedman also defined this period as the pelvic division phase. The 2nd stage may be brief in individuals with a prior vaginal delivery, while a longer duration is often noted in nulliparous parturients. Neuraxial anesthesia may also increase the duration of the 2nd stage.

This stage of labor is sometimes divided into passive and active phases. The passive phase refers to the period between the complete cervical dilation of 10 cm and the onset of active maternal expulsive efforts (ie, pushing). The passive phase, sometimes called "laboring down" or "delayed pushing," typically lasts 1 to 2 hr if used. The active phase refers to the time spent actively pushing with contractions.

According to data from Zhang's study, the 2nd stage of labor lasts, on average, 0.6 hr in nulliparous individuals without an epidural and 1.1 hr in those with an epidural. In multiparous individuals, the average duration of the 2nd stage of labor is 0.1 to 0.2 hr without an epidural and 0.3 to 0.4 hr with an epidural. The upper limit of normal, defined as the 95th percentile, was 2.8 hr in nulliparous parturients without an epidural and 3.6 hr in those with an epidural. In multiparous patients, this stage of labor was 1.1 to 1.3 hr without an epidural and 1.6 to 2.0 hr with an epidural, with higher parity associated with shorter durations.

Based on Zhang's results, the ACOG recommends defining a prolonged 2nd stage of labor as over 3 hr of pushing in nulliparous patients and beyond 2 hr of pushing in multiparous patients. However, the ACOG notes that diagnosing arrest should be individualized, considering patient preferences and clinical factors that may affect the likelihood of vaginal delivery. These factors include fetal size and position, maternal pelvis shape, the magnitude of expulsive efforts, comorbidities such as hypertension or diabetes, age, and history of previous deliveries.[15] Second-stage arrest may also be diagnosed before these thresholds are reached if fetal rotation or descent does not occur despite adequate contractions, pushing effort, and time.

Third stage of labor

The 3rd stage of labor commences when the fetus is delivered and ends with the expulsion of the placenta. Placental separation from the uterine interface is indicated by 3 cardinal signs: a gush of blood from the vagina, lengthening of the umbilical cord, and a globular-shaped uterine fundus upon palpation. Spontaneous expulsion of the placenta typically occurs within 5 to 30 min. A delivery time longer than 30 min increases the risk of postpartum hemorrhage and may indicate the need for manual removal of the placenta or other interventions.

Although traditionally not recognized, some consider the first 1 to 3 hr after delivery as the 4th stage of labor. During this time, new parents are supported while bonding with their newborn, assisted with early breastfeeding, and closely monitored for potential complications.

History and Physical

Pregnant individuals often present to the obstetrical triage unit when they suspect labor has begun. Common reasons for seeking care include painful contractions, vaginal bleeding or bloody show, and fluid leakage from the vagina. The clinician's role is to determine whether the individual is in true labor, which is defined by regular, clinically significant contractions accompanied by an objective change in cervical dilation or effacement.

Initial Evaluation and Chart Review

Upon arrival at the labor and delivery unit, vital signs, including the fetal heart rate (FHR), should be obtained and assessed for abnormalities. The parturient is typically placed on continuous cardiotocographic (CTG) monitoring, if available, for a period to ensure fetal well-being. The prenatal record must be thoroughly reviewed, noting gestational age, medical comorbidities (eg, chronic hypertension, asthma), and pregnancy complications (eg, gestational diabetes, gestational thrombocytopenia). Additionally, the record should be checked for evidence of Group B Streptococcus (GBS) colonization or any risk factors for neonatal GBS sepsis.

History

The history should include details about the onset, frequency, duration, and severity of contractions, as well as any fluid leakage or bleeding. In active labor, contractions are regular, typically occurring every 2 to 5 min, and require the parturient's focused attention. If the membranes are ruptured, the time of suspected rupture, the amount of fluid loss, and the color of the fluid should be documented. The parturient’s perception of fetal movement should also be recorded. Additionally, the time and content of the most recent oral intake, along with any allergies and current medications, should be noted. Information in the medical record should be confirmed, if possible. If the medical record is unavailable, a thorough history should be obtained, if possible.

Pelvic Examination

Next, a physical examination, including a pelvic evaluation using a sterile speculum, should be conducted. During the sterile speculum examination, clinicians assess for signs of membrane rupture, such as amniotic fluid pooling in the posterior vaginal canal. If the diagnosis is unclear, further testing, such as performing microscopy to check for ferning, measuring the pH, or laboratory testing for amniotic fluid proteins, is warranted.[16] The color of the amniotic fluid and the presence of meconium should be noted, as thick meconium-stained fluid is associated with higher rates of fetal distress during labor.

After ruling out placenta previa—via chart review or bedside ultrasound—and prelabor rupture of membranes, a sterile digital examination is typically performed to assess cervical dilation, effacement, and station. Cervical dilation is measured by locating the cervical os, spreading the fingers in a "V" shape, and estimating the distance in cm between the 2 fingers at the level of the internal cervical os. Effacement refers to cervical thinning and is assessed by estimating the percentage of remaining cervical length compared to the uneffaced cervix, which is typically about 4 cm in length. Station represents fetal descent and is assessed by determining the position of the leading fetal part relative to the maternal ischial spines. When the bony fetal presenting part aligns with the maternal ischial spine, the fetus is at 0 station. Stations proximal to the ischial spines range from -1 to -5 cm, while stations distal to the ischial spines range from +1 to +5 cm.

Abdominal Examination

In addition to the initial cervical examination, the maternal pelvis, fetal lie, presentation, position, and estimated fetal size should be assessed for maternal-fetal compatibility. The "fetal lie" refers to the orientation of the fetal spine relative to the maternal spine and may be described as longitudinal (head or buttocks presenting), transverse, or oblique. The "presentation" refers to the part of the fetus that first enters the birth canal and may be palpated on examination. In a longitudinal lie, the presentation may be either cephalic, which includes vertex, brow, face, and mentum (chin) presentations, or breech, which includes frank, complete, and footling breech presentations.

The position describes the relationship of the fetal presenting part to the maternal pelvis. For example, in a vertex presentation, if the fetal occiput is in the right anterior quadrant of the birth canal, the position is termed "right occiput anterior" (ROA).

The fetal weight and presentation may be assessed using the Leopold maneuvers, which involve systematically palpating the gravid uterus in 4 steps.[17] The 1st maneuver entails palpating the uterine fundus to determine the fetal lie and presentation by identifying which fetal pole, whether cephalic or podalic, is present at the fundus. The 2nd maneuver involves palpating the lateral surfaces of the uterus to locate the fetal spine. The 3rd maneuver assesses the engagement of the presenting part by applying gentle upward pressure just above the pubic symphysis. The final maneuver confirms the fetal position by locating the fetal forehead and occiput in the lower abdomen. A trained clinician may also estimate the fetal weight during these abdominal palpation maneuvers.

Admission and Warning Signs

Patients are typically admitted for labor if they have regular, strong contractions, cervical dilation of at least 4 to 5 cm with documented cervical change, and significant cervical effacement (eg, at least 80%). Admission is also indicated in patients with ruptured membranes and contractions. According to the ACOG Guidelines for Perinatal Care, warning signs from the initial history and examination include vaginal bleeding, acute abdominal pain, fever (temperature ≥38 °C), abnormal maternal vital signs, and abnormal FHR.

Evaluation

Admission Evaluation

Once a patient has been admitted for labor, a complete blood count and blood type and screen are commonly obtained. Additionally, testing for sexually transmitted infections, including HIV, hepatitis B and C, and syphilis, is warranted in high-risk patients. In some regions, this testing is required for all parturients upon admission for delivery. A bedside ultrasound is often performed to confirm fetal presentation and position and to assess amniotic fluid volume at the onset of labor, though this measure may not be necessary for low-risk parturients assessed by trained clinicians.

Routine Assessments During Labor

The Labour Care Guide of the World Health Organization (WHO) recommends periodically assessing the parturient's vital signs, urine output, pain, desire for pain relief, posture, and oral intake. The use of medications and intravenous fluids should be recorded, along with an assessment and plan. Labor progress is monitored by periodically reviewing the frequency and duration of contractions, cervical dilation, and fetal descent. The WHO also recommends monitoring the FHR and assessing for the presence of decelerations, the status of the fetal membranes, the fetal position, and the development of caput or molding.

Fetal Heart Rate and Contraction Monitoring

Continuous CTG is commonly used to monitor parturients. This modality allows clinicians to continuously evaluate FHR patterns for signs of fetal distress that may warrant intervention. CTG also facilitates easy assessment of contraction frequency and duration, and if an intrauterine pressure catheter is in place, it can evaluate the adequacy of contractions.

However, a 2017 Cochrane review involving over 37,000 women reconfirmed that continuous CTG does not reduce the perinatal death rate compared to intermittent auscultation in low-risk patients.[18] For this reason, intermittent auscultation of the FHR with simultaneous palpation of contractions is a reasonable option for low-risk parturients and is recommended when CTG is unavailable.[19][20] In the 2018 publication WHO Recommendations: Intrapartum Care for a Positive Childbirth Experience, the WHO recommended intermittent auscultation over continuous CTG in healthy individuals presenting in spontaneous labor.

If intermittent auscultation is used to monitor the FHR, professional guidelines from organizations such as the ACOG, the American College of Nurse-Midwives (ACNM), and the National Institute for Health and Care Excellence (NICE) recommend assessing the FHR before, during, and after a contraction at least once every 30 min during the active phase of the 1st stage of labor and at least every 15 min during the 2nd stage in low-risk pregnancies.

Monitoring Labor Progress

Monitoring labor progress typically involves serial cervical examinations every 2 to 4 hr unless concerns arise that necessitate more frequent examinations. Frequent cervical examinations carry a higher risk of infection, particularly after the membranes have ruptured.

Treatment / Management

Managing low-risk labor requires a delicate balance between supporting the natural process and minimizing potential complications.[21] In addition to regular assessments of maternal and fetal well-being (see Evaluation above), parturients should be offered interventions that improve comfort and encourage the safe progression of labor toward vaginal birth.(B3)

Management of the First Stage of Uncomplicated Labor

The 1st stage of labor begins with regular uterine contractions leading to cervical dilation and ends with full dilation at 10 cm. Parturients should be encouraged to rest and hydrate. Pain relief should be offered when appropriate, and labor progress should be monitored.

Supporting Patients During Labor

Healthy parturients with uncomplicated pregnancies should be encouraged to stay home, rest, eat, and drink as contractions begin to prepare for active labor. Early admission to the hospital during the latent phase is associated with higher rates of intervention, so admission is generally recommended once the membranes rupture or when parturients reach 4 cm to 6 cm of cervical dilation, although care should be individualized.

One-on-one support during labor is essential.[22] The NICE guidelines recommend against leaving a person in established labor alone, except for short periods or at the parturient's request. Open communication with parturients and their support team is crucial, as providing balanced information allows them to make informed choices.[23] If possible, learning about the labor process early in pregnancy helps these patients feel calmer and more confident. Additionally, encouraging parturients to personalize their labor environment, such as adjusting music, lighting, or the presence of specific support people, can enhance their birth experience.

GBS prophylaxis

Intrapartum GBS prophylaxis is recommended for laboring patients at increased risk of invasive early-onset GBS disease in the neonate. Guidelines for GBS prophylaxis vary by country, but generally, this measure is advised for individuals with a positive GBS rectovaginal culture result within the past 5 weeks, GBS bacteriuria at any time during the current pregnancy, signs of preterm labor (<37 weeks), ruptured membranes for at least 18 hr, and intrapartum fever (≥38.0 ºC).[24](B3)

Pain relief

Pain relief options should be offered to suitable candidates. Options include intravenous opioids, inhaled nitrous oxide, and neuraxial analgesia.[25] Obstetric analgesia and anesthesia are discussed in more detail elsewhere. Several nonpharmacologic methods have been developed and studied to help reduce pain during childbirth, including hydrotherapy (eg, a warm shower or water immersion), relaxation and breathing techniques, massage, warm packs, hypnosis, and sterile water injections.[26][27] (A1)

Numerous professional guidelines, including those from the ACOG, the American College of Nurse-Midwives, the Royal College of Obstetricians and Gynaecologists (RCOG), and the NICE in the U.K., concur that water immersion during the 1st stage of labor may be offered to healthy women with uncomplicated pregnancies for pain relief. Water immersion may also reduce the duration of labor and is associated with lower rates of neuraxial anesthesia. For individuals laboring in water, NICE Guideline 235 recommends a maximum water temperature of 37.5 °C (99.5 °F), with staff members monitoring the water temperature hourly.

During labor, the descending fetus pushes the Rhombus of Michaelis—the diamond-shaped area of bone formed by the three lower vertebrae and the sacrum) backward—causing a slight increase in the diameters of the pelvis. This process, however, can lead to significant lower back pain. Applying counterpressure on the sacrum can help alleviate some of this discomfort. Additionally, sterile water injections may provide relief. This procedure involves the subcutaneous injection of 0.5 mL sterile water at 4 points around the Rhombus of Michaelis.

Oral intake

Oral intake during labor is often limited to reduce the risk of aspiration, particularly in the event of an unanticipated cesarean birth. However, guidelines vary depending on the patient's risk. The ACOG and the American Society of Anesthesiologists Task Force on Obstetric Anesthesia both permit moderate amounts of clear liquids as desired by the patient but recommend avoiding solid food. Some experts, however, do not restrict solid food intake, citing the lack of significant complications associated with this measure.[28] For low-risk parturients with uncomplicated labor, NICE Guideline 235 allows a "light diet," while the WHO and the Society of Obstetricians and Gynaecologists of Canada (SOGC) recommend unrestricted oral intake as desired by the parturient.

Intravenous catheter placement and fluid administration

Intravenous catheter placement is typically performed in case emergent medication or fluid administration is required. However, continuous intravenous fluids should not be routinely given to all laboring parturients. Instead, oral hydration is recommended for patients with an adequate airway and a low risk of cesarean birth.[29] Intravenous fluids should be considered if patients have not ingested food or fluids for an extended period.(A1)

Ambulation and positioning

Low-risk parturients should generally be encouraged to ambulate freely and change positions as needed. Nurses can assist in changing positions at regular intervals to promote cervical dilation and fetal descent in parturients with neuraxial anesthesia who may have difficulty repositioning themselves. Parturients should avoid lying flat on their backs, as this position may result in aortocaval compression, which may lead to maternal hypotension and fetal distress.

During the 1st stage of labor, ambulating and staying in upright positions are generally recommended for individuals without regional anesthesia, while those with neuraxial anesthesia should be encouraged to adopt whichever position feels most comfortable. A prospective cohort study of 360 women found that parturients reported greater comfort when the maternal and fetal spines were aligned laterally, rather than opposing each other, during the latent and active phases of labor. For example, a patient may prefer the right lateral position when the fetal spine is also on the right side, such as in a right occiput anterior position.

Birthing and peanut-shaped balls are often used to help open the pelvic outlet and facilitate fetal descent. These tools have been shown to reduce pain and increase satisfaction during labor.[30][31] However, a 2019 meta-analysis involving 648 nulliparous and multiparous women in spontaneous or induced labor found that the peanut ball did not significantly shorten labor duration or reduce the incidence of vaginal or cesarean deliveries.[32] (A1)

Bladder drainage

Parturients should be encouraged to empty their bladders regularly throughout labor, though evidence suggests that bladder distension does not significantly affect labor progress.[33] Indwelling or intermittent urinary catheterization may be used when patients cannot void spontaneously, a common occurrence in those with neuraxial anesthesia. A 2020 randomized controlled trial (RCT) of 252 patients with epidural anesthesia found no difference in mode of birth or symptoms of urinary tract infection between those randomized to indwelling catheterization versus intermittent catheterization every 2 hr.[34](A1)

Interventions not recommended for routine use

Interventions that should not be performed routinely in healthy parturients in spontaneous and normally progressing labor include performing an amniotomy, continuously administering intravenous fluids, cleansing the vaginal area (eg, using chlorhexidine for the purpose of preventing infectious complications), shaving the perineum, administering enemas, and giving an antispasmodic agent. Amniotomy may be considered if labor augmentation or fetal scalp monitoring is necessary, but its routine use should be discouraged.

Management of the Second Stage of Uncomplicated Labor

The 2nd stage of labor begins with complete cervical dilation and ends with the birth of the neonate. Birth positions that promote sacral flexibility and regular position changes during this stage can decrease the duration of labor and improve fetal outcomes. Pushing may begin immediately or be delayed, each option with potential benefits and varying professional recommendations.

Birth position

Using a birth position that allows for sacral flexibility and encouraging regular position changes during the 2nd stage of labor can reduce the duration of labor by approximately 20 to 30 min compared to traditional supine positioning.[35] Parturients should be encouraged to choose a birth position, such as upright or hands-and-knees.(A1)

A Cochrane review found that, in both primiparous and multiparous individuals without an epidural, an upright birthing position shortened the 2nd stage of labor, reduced abnormal FHR patterns, and decreased operative deliveries compared to supine positions.[36] However, the review found no clear reduction in cesarean births, 3rd- or 4th-degree lacerations, or neonatal intensive care admissions, though a slight increase in patients experiencing blood loss greater than 500 mL was observed.(A1)

Early versus delayed pushing

Once the parturient reaches complete cervical dilation and effacement, pushing may begin immediately, a practice known as "early pushing." Alternatively, pushing may be delayed to allow the fetus to descend passively. The duration of delayed pushing has been studied, typically ranging from 1 to 3 hr or until the fetal head is visible at the introitus or the parturient feels a strong urge to push. Both early and delayed pushing have potential benefits and drawbacks.

A large meta-analysis involving 5,445 patients with neuraxial analgesia from 12 RCTs conducted between 1979 and 2018 found that early pushing, on average, shortened the 2nd stage of labor by 46 min compared to delayed pushing. However, early pushing resulted in 27.5 more min of pushing. Early pushing was also linked to lower rates of chorioamnionitis (9.1% versus 6.6%) and low umbilical cord pH (2.7% versus 1.3%), with variations in definitions of low pH across trials.[37] Rates of spontaneous vaginal birth, assisted vaginal birth, cesarean birth, intrapartum fever, endometritis, postpartum hemorrhage, episiotomy, 3rd- and 4th-degree perineal lacerations, 5-min APGAR scores less than 7, and neonatal respiratory morbidity were similar regardless of when pushing began.(A1)

Notably, the largest and most recent multicenter trial included in this meta-analysis, published in 2018 and involving 2,404 of the 5,445 patients, found that early pushing was associated with lower rates of postpartum hemorrhage (2.3% versus 4.0%) and suspected neonatal sepsis (3.2% versus 4.4%) compared to delayed pushing.[38] Professional guidelines on this issue vary. The ACOG recommends early pushing, while the NICE advises informing parturients about the data on early versus delayed pushing and allowing them to make an informed decision. WHO and SOGC guidelines favor delaying pushing until the parturient feels the urge to push.(A1)

Spontaneous versus directed pushing

Spontaneous pushing, where the parturient follows their instincts on when to push, is recommended for individuals without neuraxial anesthesia. Evidence is less clear for patients with neuraxial anesthesia, as a 2017 Cochrane Review found no conclusive proof supporting or refuting any specific pushing style, advising that the woman's preference, comfort, and clinical context should guide decisions.[39] Directed pushing with an open glottis (exhaling while pushing) may shorten the active 2nd stage in multiparous parturients without an epidural.(A1)

Interventions to reduce perineal trauma

To reduce perineal trauma, interventions such as warm wet compresses and perineal massage with water-soluble lubricant may be used to minimize the risk of serious perineal lacerations.[40] "Guarding" the perineum, also known as a "hands-on approach" to delivery, may help reduce 1st-degree lacerations.[41] Episiotomy should not be routinely performed.(A1)

Management of the Third Stage of Uncomplicated Labor

The 3rd stage of labor commences when the fetus is delivered and concludes with delivery of the placenta. The goals during this stage include safe placental delivery, reduction of postpartum hemorrhage risks, and cord management.

Delivery of the placenta

Gentle traction on the umbilical cord during the 3rd stage of labor may encourage placental delivery. Uterine massage is often performed, though evidence supporting its benefit is limited.[42][43](A1)

Placental separation from the uterine interface is signaled by 3 cardinal signs: blood gushing from the vagina, lengthening of the umbilical cord, and the uterine fundus exhibiting a globular shape on palpation. Spontaneous expulsion of the placenta typically occurs within 5 to 30 min. If placental delivery exceeds 30 min, the risk of postpartum hemorrhage increases, and manual removal or other interventions may be required. Delayed delivery may also raise suspicion for undiagnosed placenta accreta spectrum.

Reducing the risk of postpartum hemorrhage

Active management of the 3rd stage of labor involves administering uterotonics, typically oxytocin, which reduces the risk of postpartum hemorrhage and is recommended by several professional organizations. Oxytocin may be given as early as the delivery of the anterior shoulder or after the entire neonate or placenta is delivered. However, this medication should not be administered before the anterior shoulder is delivered, as it may worsen shoulder dystocia if present.

Cord management

Delayed cord clamping (DCC) offers neonatal benefits, such as higher initial hematocrit levels and improved iron stores at 3 to 6 months.[44][45] This measure also reduces mortality in preterm neonates.[46][47][48] A 2023 RCT involving 204 neonates found DCC between 30 and 60 seconds to be safe and effective. Meanwhile, delaying clamping for 120 seconds was associated with higher rates of neonatal polycythemia and longer phototherapy durations.[49] DCC is contraindicated in monochorionic twin gestations, maternal hemodynamic instability, and disrupted placental circulation, such as with cord avulsion or placental abruption.(A1)

Most professional organizations, including the WHO, the ACOG, the American Academy of Pediatrics, and the NICE, recommend DCC, though specifics may vary. Blood flow through the cord stops within 5 to 10 min of birth, with 75% of transfusable blood passing in the 1st min. Many providers palpate the cord and wait for pulsations to cease before applying clamps. The availability of phototherapy should be considered when delaying clamping beyond 60 seconds. Umbilical nonseverance, or leaving the cord and placenta attached until it naturally detaches in 3 to 10 days, offers no benefit and has been associated with severe neonatal infections in some case reports.[50][51][52](B2)

Differential Diagnosis

Conditions that should be considered in patients presenting with signs and symptoms suggesting the onset of labor include the following:

• Early latent labor
• False labor (ie, Braxton Hicks contractions)
• Prelabor rupture of membranes
• Placental abruption
• Uterine rupture
• Nonobstetric causes of pain, bleeding, or fluid leakage, such as urinary tract infection, cervicovaginitis, nephrolithiasis, and gastrointestinal dysfunction

Distinguishing between true labor and other conditions presenting with similar symptoms is crucial for proper care. Accurate diagnosis ensures that interventions are tailored to the patient’s specific needs and enhances maternal and neonatal safety.

Prognosis

Most healthy parturients with uncomplicated term pregnancies who begin labor spontaneously will have a vaginal birth. In a cohort including 606 nulliparous women in spontaneous labor at term, approximately 74% had a spontaneous vaginal delivery, 11% had an operative vaginal delivery, and 15% had a cesarean birth.[53]

Complications

Hemorrhage, uterine rupture, and amniotic fluid embolism can arise at any stage of labor. Uterine rupture should be suspected in parturients with sudden onset of pain and vaginal bleeding, loss of fetal station, and fetal distress, while amniotic fluid embolism typically presents with acute cardiopulmonary collapse and coagulopathy.

During the 1st stage, parturients may experience labor arrest or fetal distress, which may require cesarean or operative vaginal delivery, both of which carry increased maternal and fetal risks. Rupture of membranes, whether spontaneous or artificial, increases the likelihood of placental abruption due to rapid uterine decompression and umbilical cord prolapse. Prolonged labor, especially with prolonged rupture of membranes, raises the risk of maternal and neonatal infection. Fetal distress is often indicated by abnormal FHR patterns.

The 2nd stage of labor may be complicated by issues such as shoulder dystocia, obstetric lacerations, bony fractures, or nerve palsies in either the parturient or fetus, as well as fetal scalp hematomas and anoxic brain injuries. Postpartum hemorrhage is one of the most common complications during the 3rd stage of labor. Other potential complications include cord avulsion, retained placenta, and uterine inversion. A prolonged 3rd stage may also indicate the presence of a placenta accreta spectrum.