What is a VAC (Vacuum-Assisted Delivery) in Labor and Delivery?
A vacuum-assisted delivery (VAC) is an operative vaginal birth procedure where a suction cup is applied to the baby's scalp to assist delivery during the second stage of labor by applying traction during maternal pushing efforts. 1
How It Works
The procedure involves:
- Applying a vacuum cup (either soft or rigid/metal) to the fetal scalp at a specific location (the flexion point)
- Creating negative pressure (suction) to attach the cup firmly to the baby's head
- Applying traction (pulling force) in coordination with maternal contractions and pushing
- Guiding the baby through the birth canal when spontaneous vaginal delivery is not progressing adequately 1
When VAC is Used
Vacuum extraction is indicated for:
- Fetal distress requiring expedited delivery
- Prolonged second stage of labor (failure to progress)
- Maternal exhaustion or inability to push effectively
- Maternal conditions where prolonged pushing is contraindicated (e.g., cardiac disease) 2, 3
Key Technical Parameters
According to the 2020 RCOG guidelines, proper technique requires 1:
Maximum pulls allowed:
- 3 pulls maximum to bring the fetal head onto the pelvic floor
- 3 additional gentle pulls to ease the head over the perineum
- Total procedure should be completed within 3-4 contractions
Discontinuation criteria:
- No progressive descent with moderate traction by an experienced operator
- Two "pop-offs" (cup detachments) - less experienced operators should seek help after one pop-off
- Minimal descent after first 2 pulls - reassess cup placement, fetal position, or consider cephalopelvic disproportion
Instrument Selection Trade-offs
Soft cup vacuum extractors: 1
- Higher failure rate
- Lower neonatal scalp trauma
Rigid/metal cup vacuum extractors:
- Lower failure rate
- Higher neonatal scalp trauma risk
Vacuum vs. Forceps comparison: 1
- Vacuum has higher failure rate requiring instrument change
- Forceps cause more maternal perineal trauma
Maternal Risks
- Episiotomy: 50-60% of cases
- Significant vaginal/vulvar tears: 10%
- Obstetric anal sphincter injury (OASI): 1-4%
- Postpartum hemorrhage: 10-40%
Neonatal Risks
- Cephalohematoma: 1-12% (predominantly with vacuum)
- Scalp lacerations: 10%
- Retinal hemorrhage: 17-38% (more common with vacuum than forceps)
- Jaundice/hyperbilirubinemia: 5-15%
- Subdural or cerebral hemorrhage: approximately 1 in 860 vacuum births
Critical Safety Considerations
Sequential instrument use (attempting forceps after failed vacuum or vice versa) significantly increases risks 1:
- Increased neonatal trauma (intracranial hemorrhage risk increases to 1 in 256)
- Increased OASI risk for mothers
- Should only be considered at low station with careful risk-benefit assessment
Gestational age restrictions: 1
- Avoid vacuum at <32 weeks gestation
- Use caution at 32-36 weeks gestation
Operator Requirements
- Must be performed by or supervised by an experienced operator with demonstrated competency
- Midpelvic or rotational vacuum deliveries require experienced operators from the outset
- Training must include theoretical knowledge, simulation, and supervised clinical experience
- Low-pelvic, non-rotational procedures can be performed in birth rooms
- Higher-risk procedures should be attempted in operating theaters with immediate access to cesarean delivery
Common Pitfalls to Avoid
- Incorrect cup placement - increases failure rate 4-fold and neonatal trauma risk
- Treating "pop-offs" as safety features - they can cause fetal vascular injury if occurring during full traction
- Continuing beyond appropriate limits - know when to abandon and proceed to cesarean
- Inadequate assessment of fetal position, station, and engagement before starting
- Using vacuum when forceps would be more appropriate based on clinical circumstances and operator skill
The procedure requires careful patient selection, proper technique, and knowing when to discontinue to optimize both maternal and neonatal outcomes.