Protracted and arrested labor represent significant challenges in obstetric practice, demanding a thorough understanding of their etiologies, accurate diagnostic approaches, and judicious management strategies. These conditions, characterized by slower-than-expected progress in labor or a complete cessation of cervical dilation and fetal descent, can lead to increased maternal and neonatal morbidity if not identified and addressed promptly.
Etiology of Protracted or Arrested Labor
The etiology of protracted or arrested labor is multifactorial, arising from an imbalance in the “5 Ps” of labor: passenger (fetus), passage (pelvis), powers (uterine contractions), position (maternal posture), and psyche (maternal stress). Disruptions in any or a combination of these factors can impede the normal mechanism of labor.
1. Passenger (Fetus) Abnormalities:
- Fetal Malposition: The most common fetal cause is malposition, particularly occiput posterior (OP) or occiput transverse (OT) presentations. In OP, the widest diameter of the fetal head engages the pelvis, hindering efficient descent and rotation. OT positions also present a less favorable diameter. Other malpositions include brow or face presentations, where the presenting diameter is significantly larger than the suboccipitobregmatic diameter, making engagement and descent difficult.
- Fetal Malpresentation: While less common than malposition, frank breech or complete breech presentations can also contribute to prolonged labor, especially if the fetus is large or the pelvis is not optimally shaped. Compound presentations (e.g., arm presenting with the head) are also obstructive.
- Fetal Macrosomia: A fetus weighing over 4000-4500 grams is considered macrosomic. While not all macrosomic fetuses lead to dystocia, their increased size can lead to cephalopelvic disproportion (CPD) or make rotation more challenging, particularly in the OP position. Shoulder dystocia, a true obstetric emergency, is also a significant risk with macrosomia.
- Fetal Abnormalities: Congenital anomalies such as hydrocephalus (excessive fluid in the fetal brain) can significantly increase the fetal head circumference, leading to CPD. Other rare fetal anomalies affecting the skeleton or soft tissues can also impede passage through the birth canal.
2. Passage (Pelvis) Abnormalities:
- Pelvic Deformity: Anatomical abnormalities of the maternal pelvis, often due to conditions like rickets in childhood, trauma, or congenital conditions, can reduce the pelvic capacity or alter its shape, making passage of the fetus difficult. This can manifest as a contracted pelvis (e.g., platypelloid, android, or anthropoid shapes) which may be inadequate for the fetal head, even if the fetus is of normal size.
- Pelvic Contractures: Even in a structurally normal pelvis, soft tissue dystocia can occur. This includes a poorly relaxed pelvic floor, leading to increased resistance to fetal descent. Excessive maternal tissue (obesity) can also contribute to a more tortuous birth canal.
- Cephalopelvic Disproportion (CPD): This is a critical concept where the fetal head is too large to fit through the maternal pelvis, or the maternal pelvis is too small to accommodate the fetal head. CPD can be absolute (head truly too large) or relative (head malpositioned or molding inadequately). It is a common cause of protracted descent and arrest.
3. Powers (Uterine Contractions) Abnormalities:
- Hypotonic Uterine Dysfunction: This is characterized by infrequent, short, or weak contractions that are insufficient to effect cervical change. It is more common in the active phase of labor, particularly in multiparous women or with overdistended uteri (e.g., polyhydramnios, multiple gestations). Psychosocial factors and excessive analgesia can also contribute to hypotonic dysfunction.
- Hypertonic Uterine Dysfunction: In contrast, hypertonic dysfunction involves contractions that are frequent, uncoordinated, and often very painful, but not effective in dilating the cervix. This typically occurs in the latent phase of labor. The uncoordinated nature of these contractions prevents efficient cervical effacement and dilation.
- Incoordinate Uterine Action: This refers to contractions that are not synchronized or of the appropriate intensity and duration to promote labor progression. The uterus may contract in segments rather than as a coordinated unit, leading to poor expulsive forces.
4. Position (Maternal Posture) and Interventions:
- Maternal Position: Prolonged lying in a supine position can impede labor progress by reducing blood flow to the uterus and fetus and by compromising the biomechanics of labor. Upright positions, such as standing, walking, or squatting, can facilitate fetal descent by gravity and improve pelvic diameters.
- Epidural Analgesia: While beneficial for pain relief, epidural anesthesia, particularly when initiated early in labor, can sometimes lead to prolonged second stage due to reduced urge to push, altered pelvic floor mechanics, and potential motor blockade affecting pushing efforts. However, it is important to note that the impact of epidurals on labor duration is complex and debated.
- Induction of Labor: Early induction of labor, especially in nulliparous women with an unfavorable cervix, can sometimes lead to protracted labor if the uterus does not respond effectively to oxytocin stimulation.
5. Psyche (Maternal Stress and Anxiety):
- Fear and Anxiety: Excessive fear, anxiety, and stress can lead to the release of catecholamines, which can inhibit uterine contractions and slow labor progression. This is particularly relevant in the latent phase of labor. The “fight or flight” response diverts energy away from the uterus.
Diagnosis of Protracted or Arrested Labor
The diagnosis of protracted or arrested labor relies on careful monitoring of labor progress and a systematic assessment of the contributing factors. It is crucial to distinguish these conditions from the normal variations in labor duration, especially in the latent phase.
Key Diagnostic Tools and Assessments:
1. Partograph: The partograph is a graphical record of the progress of labor, documenting cervical dilation, effacement, descent of the fetal head, uterine contractions, and maternal vital signs.
- Protracted Labor: Defined by deviations from the expected progress on the partograph. For nulliparous women, cervical dilation in the active phase (typically after 6 cm) is expected to be at least 1.2 cm per hour, and for multiparous women, at least 1.5 cm per hour. A labor that progresses at a rate slower than this is considered protracted. Similarly, slowed fetal descent or lack of station changes can also indicate protracted labor.
- Arrested Labor: Defined by a complete cessation of progress. The obstetric consensus is that arrest of dilation occurs when there is no cervical change for 4 hours in the presence of adequate uterine contractions (defined as at least 3-5 contractions every 10 minutes, each lasting 40-60 seconds), or 6 hours if uterine contractions are suboptimal. Arrest of descent is diagnosed when there is no descent of the presenting part for 1 hour in the second stage of labor, with adequate maternal pushing efforts.
2. Cervical Examination: Regular cervical examinations are fundamental to assessing labor progress.
- Cervical Dilation: The opening of the cervix from 0 to 10 cm.
- Cervical Effacement: The thinning of the cervix, measured in percentage from 0% to 100%.
- Station: The level of the presenting part of the fetus in relation to the maternal ischial spines. This is measured in centimeters, with 0 station at the ischial spines, negative numbers (-1 to -5) above, and positive numbers (+1 to +5) below.
3. Uterine Contraction Assessment:
- Frequency: Number of contractions in a 10-minute period.
- Duration: Length of each contraction in seconds.
- Intensity: Subjective assessment of the strength of contractions (mild, moderate, strong) or objective measurement via intrauterine pressure catheter. Adequate contractions are generally considered to be at least 3-5 contractions in 10 minutes, each lasting 40-60 seconds and of moderate to strong intensity.
4. Fetal Assessment:
- Fetal Heart Rate Monitoring: Continuous fetal monitoring is essential to assess fetal well-being. Prolonged labor carries an increased risk of fetal distress, evidenced by persistent bradycardia, late decelerations, or loss of variability.
- Fetal Head Station and Molding: Palpating the fetal head during vaginal examination provides information about its descent and engagement. Significant molding (the overriding of fetal skull bones) can indicate a tight fit between the fetal head and the maternal pelvis.
5. Pelvic Assessment (Clinical Pelvimetry): While not as precise as radiological pelvimetry (which is rarely performed today), a clinical assessment of the pelvis can be performed to identify potential bony abnormalities or contractures. This includes:
- Diagonal Conjugate: Palpating the anterior aspect of the sacrum and the symphysis pubis.
- Interspinous Diameter: Estimating the distance between the ischial spines.
- Subpubic Angle: Assessing the angle formed by the pubic rami.
6. Assessment of the “Passenger”:
- Fetal Lie and Presentation: Determined by abdominal palpation (Leopold’s maneuvers) and confirmed by vaginal examination or ultrasound. Malpresentations (breech, transverse lie) and malpositions (occiput posterior) are key considerations.
- Fetal Size (Estimated Fetal Weight – EFW): Ultrasound can provide an estimate of fetal weight. However, estimations can be inaccurate, particularly in macrosomic fetuses. Clinical suspicion of macrosomia or a history of previous macrosomic infant or diabetic mother should raise suspicion.
7. Maternal Factors:
- Maternal Fatigue and Anxiety: Can be assessed through observation and communication.
- Epidural Analgesia: Note the timing and dosage of epidural administration, as it can influence pushing efforts and labor duration.
Differential Diagnosis:
It is important to differentiate protracted or arrested labor from:
- Latent Phase Prolongation: The latent phase (0-6 cm dilation) can be highly variable, especially in nulliparous women, and can last longer than 20 hours. Diagnosis of arrest generally requires no progress in the active phase.
- False Labor: Characterized by irregular, non-progressive contractions that do not lead to cervical change.
Treatment of Protracted or Arrested Labor
The management of protracted or arrested labor is guided by a systematic approach aimed at identifying the underlying cause, ensuring maternal and fetal well-being, and ultimately facilitating a safe delivery. The decision-making is often complex and depends on various factors including parity, gestational age, fetal well-being, maternal health, and the specific etiological factors identified.
1. Addressing Uterine Powers:
- Augmentation of Labor with Oxytocin: This is a primary intervention for hypotonic uterine dysfunction and can also be used in cases of protracted labor where contractions are suboptimal.
- Mechanism: Oxytocin is a synthetic form of the natural hormone that stimulates uterine contractions. It is administered intravenously, typically starting with a low dose and titrating upwards based on uterine response and maternal/fetal tolerance.
- Protocol: Protocols vary, but a common approach involves starting at 1-2 mU/min and increasing by 1-2 mU/min every 15-40 minutes until adequate contractions (e.g., 3-5 contractions in 10 minutes, each lasting 40-60 seconds) are achieved or a maximum dose is reached.
- Monitoring: Close monitoring of uterine activity and fetal heart rate is crucial during oxytocin augmentation to detect hyperstimulation or fetal distress.
- Amniotomy (Artificial Rupture of Membranes – AROM): When the amniotic membranes are intact, their rupture can sometimes stimulate or accelerate labor.
- Mechanism: AROM can release prostaglandins, which aid in cervical ripening and effacement. It can also allow for better molding of the fetal head to the pelvis once the “bag of waters” is no longer a barrier.
- Indications: Often performed in conjunction with oxytocin augmentation, particularly if there is slow cervical dilation beyond 6 cm and favorable fetal lie.
- Contraindications: Rupture of membranes is contraindicated in cases of active genital herpes infection, placenta previa, or when there is significant suspicion of cephalopelvic disproportion. It requires careful monitoring for umbilical cord prolapse and fetal distress.
2. Addressing Pelvic Passage and Fetal Passenger Issues:
- Positional Changes: Encouraging maternal movement and upright positions can significantly improve labor progress.
- Benefits: Gravity assists fetal descent, increases pelvic diameters, and can improve uterine efficiency.
- Examples: Walking, squatting, side-lying, hands-and-knees position. Avoiding prolonged supine positioning is recommended.
- Management of Cephalopelvic Disproportion (CPD): If CPD is strongly suspected (e.g., persistent lack of descent despite adequate contractions, large for gestational age fetus, bony pelvic abnormalities), operative delivery is usually indicated.
- Forceps or Vacuum Extractor Delivery: If the fetus is low enough in the pelvis and there are no other contraindications, assisted vaginal delivery may be considered once the cervix is fully dilated and effaced, and the fetal head is at or below the ischial spines. The success of these interventions depends on the degree of CPD and the skill of the accoucheur.
- Cesarean Section: In cases of definite CPD, significant fetal malpresentation, or failure of conservative measures, a cesarean section is the definitive treatment. This is particularly true for arrested labor where there is concern for fetal compromise due to prolonged labor.
3. Management of Fetal Malposition/Malpresentation:
- Manual Rotation: For occiput posterior (OP) presentations, manual rotation to the occiput anterior (OA) position by an experienced clinician may be attempted during labor. This is more effective when the fetal head is lower in the pelvis.
- Cesarean Section: If manual rotation is unsuccessful, or if the malpresentation or malposition is contributing significantly to labor arrest, a cesarean section is often required.
4. Addressing Maternal Factors:
- Pain Management: Adequate pain relief is crucial. While early and aggressive epidural use can sometimes be associated with longer labor, judicious use with mobility support (e.g., rocking chair, walking epidurals) can be effective.
- Support and Reassurance: Addressing maternal anxiety and fatigue through continuous labor support from partners, doulas, or nurses can positively impact labor progress.
- Fluid and Nutritional Support: Maintaining adequate hydration and energy levels is important for a laboring patient.
5. “Hands-Off” vs. “Active Management” Debate:
There is ongoing discussion regarding the optimal management approach. Some advocate for a more “hands-off” approach, allowing labor to progress with minimal intervention, particularly in the early active phase, while others prefer more active management with earlier augmentation and intervention to prevent prolonged labor and its potential complications. Current guidelines generally support a balanced approach, emphasizing vigilant monitoring and prompt intervention when indicated.
6. Second Stage Management:
- Protracted Second Stage: Defined by prolonged pushing. Management may involve encouraging active pushing, positional changes, and considering augmentation with oxytocin. If progress is not made after a reasonable period (e.g., 1-2 hours of pushing with epidural, less without), assisted delivery or cesarean section should be considered.
- Arrested Second Stage: This is a more immediate indication for intervention, typically an assisted vaginal delivery or cesarean section, depending on the clinical context.
Important Considerations:
- Fetal Well-being: Continuous fetal heart rate monitoring is paramount throughout the management of protracted labor. Signs of fetal distress necessitate urgent intervention.
- Maternal Fatigue and Trauma: Prolonged labor can lead to maternal exhaustion, increased risk of infection, and trauma to the birth canal and pelvic floor.
- Decision-Making: The management plan should be individualized, taking into account all contributing factors and involving shared decision-making with the patient whenever possible.
In conclusion, protracted and arrested labor are complex obstetric events with diverse etiologies. A comprehensive understanding of the “5 Ps,” coupled with vigilant monitoring and a systematic diagnostic approach, is essential for accurate identification. Treatment strategies should be tailored to the underlying cause, prioritizing maternal and fetal well-being, and may involve augmentation, positional changes, or operative intervention.
References
- Cunningham, F. G., Leveno, K. J., Bloom, S. L., Spong, C. Y., & Dashe, J. S. (2018). Williams Obstetrics (25th ed.). McGraw-Hill Education.
- American College of Obstetricians and Gynecologists. (2014). Nausea and Vomiting of Pregnancy. Practice Bulletin No. 153. Obstetrics & Gynecology, 123(3), 675–687. (While this reference is for NVP, it highlights the format of ACOG bulletins which are standard references in obstetrics. For labor specific topics, ACOG Practice Bulletins such as “Management of Normal Labor” or “External Cephalic Version” would be relevant).
- Hughes, S. R. (2021). Labor Dystocia. In S. R. Hughes (Ed.), Difficult Labor and Delivery (pp. 3-13). Springer.
- Frigo, A. M., & Frigo, L. C. (2010). Dystocia. In Current Diagnosis and Treatment: Obstetrics and Gynecology (10th ed.). McGraw-Hill.
- Enkin, M. W., Maru, A., & Neil, S. C. (2007). A Guide To Effective Care in Pregnancy and Childbirth (3rd ed.). Oxford University Press.
- Raynor, B. D. (2021). Normal Labor and Delivery. In B. D. Raynor (Ed.), Obstetrics and Gynecology (pp. 304-317). Elsevier.
