Risk of Fetal/Neonatal Injury in Assisted Vaginal Birth
The risk of fetal/neonatal injury during assisted vaginal birth is significantly increased when there is sequential use of vacuum and then forceps.
Evidence Supporting This Answer
Sequential use of vacuum and forceps is associated with substantially higher risks of neonatal trauma compared to either instrument used alone. According to high-quality research evidence, this sequential approach:
- Increases the risk of intracranial hemorrhage (relative risk 3.9) 1
- Increases the risk of facial nerve injury (relative risk 13.3) 1
- Increases the risk of seizures (relative risk 13.7) 1
- Increases the risk of brachial plexus injuries (relative risk 3.2) 1
Importantly, the combined risk of sequential instrument use is greater than the sum of individual risks from each instrument for several serious complications, including intracranial hemorrhage and facial nerve injury 1.
Why Sequential Use Is Particularly Dangerous
The sequential use of instruments indicates:
- Failed initial attempt: The need for a second instrument suggests difficulty with the first attempt, which may indicate a challenging delivery that already carries higher risk
- Cumulative trauma: Each instrument application adds mechanical stress to fetal tissues
- Prolonged instrumentation: Extended duration of instrumental manipulation increases risk
A cohort study found that sequential instrument use was associated with greater maternal and neonatal morbidity than single instrument use, with significantly higher rates of umbilical artery pH <7.10 (adjusted OR 3.3) 2.
Other Risk Factors in Assisted Vaginal Birth
While sequential instrument use poses the highest risk among the options presented, other factors that increase risk include:
- Prolonged second stage: While prolonged second stage (>90 minutes) increases risk, it's not as significant as sequential instrument use
- Instrument choice: Metal vacuum cups have higher rates of neonatal trauma than forceps, while forceps have higher rates of maternal trauma 3
Incorrect Options
- Fetus in flexed attitude: A flexed fetal attitude is actually the normal position for delivery and is associated with fewer complications than deflexed positions
- Operator completed ALARM course: Training programs like ALARM are designed to improve outcomes, not increase risks 4
Recommendations for Practice
To minimize fetal/neonatal injury during assisted vaginal birth:
- Avoid sequential instrument use whenever possible
- If the first instrument fails, consider proceeding to cesarean delivery rather than attempting a second instrument
- Ensure proper training in instrument selection and application
- Consider the specific clinical circumstances when choosing between forceps and vacuum
Conclusion
Among the options presented, sequential use of vacuum and then forceps poses the greatest risk of fetal/neonatal injury during assisted vaginal birth, with compelling evidence showing significantly increased rates of serious complications compared to other approaches 1, 2.