What is the best course of action for a patient in the second stage of labor with a fully dilated and effaced cervix, ruptured membranes, cephalic presentation, station 0, small fontanel, and 1 cm of caput after an hour of adequate contractions?

Management of Arrested Second Stage Labor

Administer oxytocin augmentation as the first-line intervention for this patient with arrested second stage labor, as cephalopelvic disproportion (CPD) must first be ruled out, and oxytocin has a 92% success rate for achieving vaginal delivery when CPD is not present. 1

Clinical Assessment

This patient presents with classic arrested second stage labor:

• Fully dilated cervix with adequate contractions for one hour
• No descent (station remains at 0)
• Development of 1 cm caput succedaneum, indicating prolonged pressure without progress 2

The presence of caput formation without descent is a warning sign that requires immediate evaluation for CPD before proceeding with any intervention. 2

Critical Evaluation for Cephalopelvic Disproportion

Before initiating any treatment, you must assess for CPD, which occurs in 25-30% of active phase arrest cases and 40-50% of arrested labor cases: 2, 1

• Examine for excessive molding, deflexion, or asynclitism of the fetal head 2
• Assess fetal position - the small fontanel at left transverse position indicates occiput transverse, a malposition associated with arrest 2
• Evaluate maternal pelvic adequacy through cephalopelvimetry 2
• Rule out fetal macrosomia (estimated weight 3200g is within normal range) 2

Management Algorithm

If CPD is Excluded:

Oxytocin augmentation is the evidence-based first-line treatment: 1, 3

• Start oxytocin at 1-2 mU/min, increasing by 1-2 mU/min every 15 minutes 3, 4
• Target 7 contractions per 15 minutes, maximum dose 36 mU/min 3
• Monitor continuously for uterine hyperstimulation and fetal distress 1, 3, 4
• Discontinue oxytocin immediately if signs of fetal distress or uterine hyperactivity occur 4

Reassess progress after adequate oxytocin augmentation: 2, 1

• If no progress after 2 hours (recent evidence suggests this is safer than waiting 4 hours), proceed to cesarean delivery 2
• If progress occurs, continue oxytocin and monitor closely 1

If CPD is Present or Cannot be Excluded:

Proceed directly to cesarean delivery - oxytocin is contraindicated when CPD is suspected, as it increases the risk of uterine rupture, maternal hemorrhage, and fetal injury. 2, 3

Why Other Options Are Inappropriate

Operative vaginal delivery (forceps or vacuum) is contraindicated at station 0: 2

• Both require the fetal head to be at least at +2 station for safe application
• Attempting operative delivery at station 0 with caput formation risks severe maternal and fetal trauma

Observation for another hour without intervention is inappropriate: 2, 1

• One hour of adequate contractions without progress already defines arrest
• Further observation without augmentation increases risk of maternal exhaustion, chorioamnionitis, and fetal compromise
• The presence of caput indicates prolonged pressure that will worsen with continued observation

Common Pitfalls to Avoid

• Never attempt operative vaginal delivery when the head is at station 0 - this is a recipe for catastrophic maternal and fetal injury 2
• Do not administer oxytocin if CPD cannot be excluded - this can lead to uterine rupture and severe hemorrhage 2, 3
• Do not delay intervention hoping for spontaneous progress - arrested labor rarely resolves without intervention once established 2
• Recognize that occiput transverse position may require manual rotation or may indicate underlying CPD 2

Monitoring During Oxytocin Administration

• Continuous fetal heart rate monitoring 1, 3, 4
• Serial cervical examinations every 2 hours to assess descent and rotation 3
• Monitor contraction frequency, duration, and intensity 3
• Assess for signs of uterine hyperstimulation (>5 contractions in 10 minutes) 4