Management of Arrest in Cervical Dilation Secondary to Pelvic Inlet Contraction
When arrest of cervical dilation occurs secondary to pelvic inlet contraction (cephalopelvic disproportion), cesarean delivery is the safest and most prudent option—oxytocin augmentation is contraindicated and vaginal delivery should not be attempted. 1
Critical First Step: Confirm Cephalopelvic Disproportion
Thorough cephalopelvimetry is mandatory before any management decision. 1 The question explicitly states pelvic inlet contraction is present, which constitutes CPD and fundamentally changes management:
- CPD occurs in 40-50% of all active phase arrest cases, making it the most important factor to evaluate 1
- Clinical signs of CPD include: increasingly marked molding, deflexion, asynclitism of the fetal head without descent, and failure of the fetal head to descend despite contractions 1
- Serial suprapubic palpation of the base of the fetal skull is essential to differentiate true descent from molding alone 1
Why Cesarean Delivery is Mandatory with CPD
The risks of maternal and fetal damage are too great to attempt vaginal delivery when CPD is present or cannot be ruled out with reasonable certainty. 1 The 2023 American Journal of Obstetrics and Gynecology guidelines explicitly state:
- "It is better to err on the side of intervention by CD in the presence of uncertainty about potential harm than to allow labor in the false hope that safe vaginal delivery may occur" 1
- When CPD is confirmed with arrest disorder, "CD is a more prudent and safer choice" because vaginal delivery is "unlikely to be achievable, let alone safely" 1
Why Oxytocin is Contraindicated
If associated with evidence of CPD, ecbolic agents are best avoided. 1 Attempting oxytocin augmentation in the presence of CPD:
- Risks uterine hyperstimulation without achieving vaginal delivery 1
- Increases maternal trauma (uterine rupture risk, severe lacerations) 1
- Increases fetal trauma (excessive molding, potential asphyxia) 1
- Delays definitive treatment while worsening outcomes 1
Common Pitfall to Avoid
Do not confuse arrest of dilation WITHOUT CPD (where oxytocin trial is appropriate) with arrest WITH CPD (where oxytocin is contraindicated). 1 The management algorithm diverges completely based on CPD presence:
If CPD is ABSENT (not this scenario):
- Oxytocin augmentation for 4 hours (or 2 hours if ≥8 cm dilation) is appropriate 1
- 92% vaginal delivery success rate can be achieved 2
- Target adequate contractions (≥200 Montevideo units) 1, 2, 3
If CPD is PRESENT (this scenario):
- Proceed directly to cesarean delivery 1
- Do not waste time with oxytocin trial 1
- Do not perform amniotomy as treatment 1
Additional Risk Factors That Support Cesarean Decision
When CPD is present, be aware of compounding factors that further increase risk: 1
- Maternal diabetes and obesity
- Fetal macrosomia
- Malposition (occiput posterior or transverse)
- Malpresentation (brow presentation)
- Marked asynclitism
- Excessive molding without descent
Timing Considerations
Astute clinicians will often recognize CPD and proceed to cesarean delivery before formal arrest criteria are met, especially when malposition or excessive molding is noted on examination. 1 While formal arrest diagnosis requires 2-4 hours of no cervical change 1, do not delay cesarean delivery if CPD is evident, as waiting increases maternal and fetal morbidity without improving outcomes.
Evidence Strength Note
Recent evidence from 2021 suggests that when cervical dilation is ≥8 cm, allowing arrest duration <4 hours (rather than ≥4 hours) is associated with decreased risks of cesarean delivery, chorioamnionitis, and adverse neonatal outcomes 4. However, this evidence applies only to cases WITHOUT CPD—when CPD is present, duration of arrest is irrelevant because vaginal delivery is not safely achievable regardless of time allowed. 1