What is an indication for undertaking an assisted vaginal delivery in a woman of childbearing age with no significant medical history and a reassuring fetal heart rate?

Assisted Vaginal Delivery Indications

The correct answer is C: Category III fetal heart rate tracing is an indication for assisted vaginal delivery when the fetal head is engaged and all prerequisites for safe operative vaginal delivery are met. 1, 2

Understanding the Question

This question tests knowledge of appropriate indications for assisted vaginal delivery (forceps or vacuum extraction). Let me analyze each option systematically:

Analysis of Each Option

Option A: Suspected Cephalopelvic Disproportion - CONTRAINDICATION

• Suspected cephalopelvic disproportion is an absolute contraindication to operative vaginal delivery and requires cesarean section. 1, 2
• Signs of CPD include marked molding, deflexion, or asynclitism of the fetal head without descent. 1
• This is a critical safety issue—attempting assisted vaginal delivery with CPD risks severe maternal and fetal trauma.

Option B: Brow Presentation - CONTRAINDICATION

• Fetal malpresentation is a contraindication to assisted vaginal delivery. 3
• Brow presentation specifically cannot be safely delivered vaginally with instruments due to the increased presenting diameter.
• This requires either conversion to face or occiput presentation, or cesarean delivery.

Option C: Category III Fetal Heart Rate Tracing - CORRECT INDICATION

• Category III (formerly "nonreassuring") fetal heart rate tracing is a valid indication for expedited delivery, including assisted vaginal delivery when appropriate. 1, 2, 3
• When the fetal head is already engaged in the vaginal canal, operative vaginal delivery is often safer and faster than emergency cesarean. 2
• Continuous electronic fetal heart rate monitoring should be maintained throughout the operative delivery. 1, 2
• This represents one of the most common indications for primary cesarean delivery (27.3% of cases), but when conditions are favorable for assisted vaginal delivery, this approach can safely prevent cesarean. 4

Option D: Prolonged First Stage of Labor - NOT AN INDICATION

• Prolonged first stage of labor is not an indication for assisted vaginal delivery because assisted vaginal delivery can only be performed during the second stage of labor when the cervix is fully dilated. 5, 3
• First stage labor dystocia is managed with oxytocin augmentation or cesarean delivery, not operative vaginal delivery. 5, 6
• Among women with failure to progress, 42.6% of primiparous women never progressed beyond 5 cm before cesarean delivery. 4

Key Prerequisites for Safe Assisted Vaginal Delivery

Before undertaking any assisted vaginal delivery, the following conditions must be met:

• Full cervical dilation (10 cm) - this is why first stage arrest is not an indication. 5, 4
• Engaged fetal head with known position - the station and position must be accurately assessed. 1
• No evidence of cephalopelvic disproportion - assess for molding, deflexion, or asynclitism. 1, 2
• Vertex presentation - malpresentations like brow are contraindications. 3
• Adequate maternal pelvis - clinical pelvimetry assessment. 1

Clinical Context: Second Stage Management

• Among women who reached the second stage of labor, 17.3% underwent cesarean delivery for arrest of descent before 2 hours, and only 1.1% were given a trial of operative vaginal delivery. 4
• This represents a significant missed opportunity—allowing adequate time for the second stage and encouraging operative vaginal delivery when appropriate are important strategies to reduce primary cesarean delivery rates. 4
• Operative vaginal delivery has an increasingly important role in tempering cesarean birth rates when strict safety conditions are met. 6

Common Pitfall to Avoid

The most critical error is attempting assisted vaginal delivery with suspected cephalopelvic disproportion (Option A). This is dangerous and can result in severe maternal trauma (including obstetric anal sphincter injury, bladder injury, or uterine rupture) and fetal injury (skull fractures, intracranial hemorrhage). 1 Always thoroughly assess for CPD before attempting operative vaginal delivery.