A 32-year-old primigravida at 39 weeks gestation presents to the labor ward in active labor. On examination, the cervix is 6 cm dilated, fully effaced, and the fetal head is at −2 station. Cardiotocography shows a baseline fetal heart rate of 140 bpm with good variability and no decelerations. After 6 hours of augmentation with oxytocin, the cervix remains at 6 cm with the head still at −2 station. What is the most appropriate next step in management?

Explanation

## Clinical Scenario Analysis This patient meets the diagnostic criteria for **arrest of dilation** — a prolonged latent phase or active phase arrest disorder. ### Diagnostic Criteria for Arrest Disorders **Key Point:** Arrest of dilation is defined as: - No cervical change for ≥4 hours in the active phase (cervix ≥6 cm) with adequate uterine contractions (≥200 Montevideo units), OR - No cervical change for ≥6 hours with inadequate contractions In this case: - Patient is in active labor (cervix 6 cm, fully effaced) - After 6 hours of oxytocin augmentation, NO progress (still 6 cm, −2 station) - Fetal heart rate is reassuring (no indication of fetal distress) ### Management of Arrest of Dilation **High-Yield:** According to ACOG guidelines, once arrest of dilation is diagnosed with a reassuring fetal heart rate tracing: 1. Confirm adequate uterine contractions (≥200 Montevideo units) — already augmented with oxytocin 2. Confirm maternal and fetal well-being — confirmed (reassuring CTG) 3. **Proceed to cesarean section** — this is the standard of care **Clinical Pearl:** Continued expectant management or further augmentation beyond the diagnostic window increases maternal morbidity (infection, hemorrhage) and does not improve neonatal outcomes. ### Why Cesarean Section Now? - Prolonged labor increases risk of: - Chorioamnionitis - Postpartum hemorrhage - Maternal exhaustion - Fetal acidosis (despite current reassuring tracing) - The diagnosis is clear and management is evidence-based - Fetal status is reassuring, so urgent delivery (not emergent) is appropriate [cite:ACOG Practice Bulletin 49]