How is arrest of cervical dilatation diagnosed?

Diagnosis of Arrest of Cervical Dilatation

Arrest of cervical dilatation is diagnosed when there is no cervical change for at least 4 hours despite adequate uterine contractions (≥200 Montevideo units) after the patient has reached at least 6 cm of cervical dilatation in the active phase of labor. 1, 2

Diagnostic Criteria

Minimum Requirements for Diagnosis

• Cervical dilatation must be ≥6 cm to diagnose active phase arrest 1, 2
• No cervical change for ≥4 hours with adequate contractions, OR
• No cervical change for ≥6 hours with inadequate contractions despite oxytocin augmentation 1, 2

Defining Adequate Uterine Contractions

• Montevideo units ≥200 measured by internal uterine pressure catheter over 10-minute intervals 3
• However, contractile patterns alone are of limited diagnostic value for determining labor phase or normalcy—the dilatation pattern graphed serially is the most reliable indicator 3

Diagnostic Process

Serial Cervical Examinations

• Perform vaginal examinations at least every 2 hours to accurately track the rate of cervical dilatation 3
• Graph serial measurements of cervical dilatation to create labor curves that provide diagnostic and prognostic information 4
• The active phase begins when the rate of dilatation transitions from the flat slope of latent phase to more rapid progression, regardless of the specific degree of dilatation achieved 3

Clinical Assessment Components

• Document cervical dilatation, effacement, and fetal station at each examination 1, 2
• Monitor fetal heart rate continuously to ensure normal fetal well-being during the assessment period 1, 2
• Assess for adequate uterine contractions using internal pressure monitoring when possible 2

Important Clinical Considerations

Timing Matters by Cervical Dilatation

• At 6-7 cm dilatation, allowing arrest duration ≥4 hours is reasonable as it is not associated with increased adverse neonatal outcomes 5
• At 8-9 cm dilatation, arrest duration <4 hours is associated with significantly better maternal and neonatal outcomes compared to 4-6 hours (decreased cesarean delivery, chorioamnionitis, and neonatal complications) 5

Common Pitfalls to Avoid

• Do not diagnose arrest before 6 cm dilatation—this represents latent phase, not active phase arrest 1, 2
• Do not rely on contraction assessment alone (palpation or Montevideo units) to determine if active phase has begun, as contractions increase inconsistently and provide limited diagnostic value 3
• Ensure adequate time has elapsed—95% of women who underwent cesarean for arrest had either ≥6 cm dilatation or received labor stimulation ≥6 hours prior to delivery 6

Underlying Factors to Evaluate

When arrest is diagnosed, assess for:

• Cephalopelvic disproportion (CPD), which occurs in 25-30% of active phase arrest cases 1, 2
• Fetal malposition or malpresentation 3
• Excessive neuraxial analgesia 3
• Maternal factors: obesity, advanced maternal age, diabetes 3, 7
• Fetal macrosomia 7
• Intrauterine infection 3