PURPOSE:

• ACOG and SMFM are advocating operative vaginal delivery to reduce cesarean section rates
• However, further research is needed on perinatal and maternal outcomes based on pelvic station
• Muraca et al. (BJOG, 2017) sought to quantify risks associated with operative vaginal delivery at midcavity station

METHODS:

• Population-based, retrospective cohort study from the British Columbia Perinatal Data Registry (2004-2014)
• 37 to 41 week gestation singletons, 2^nd stage of labor
• Definition of operative ‘midcavity’ delivery
  • Operative vaginal delivery by forceps, vacuum and sequential instruments in cases where the head was engaged and the leading point of the fetal skull was above the +2 cm station but below the 0 cm station
• Primary outcomes
  • Composite severe perinatal morbidity/mortality
  • Composite severe maternal morbidity
• Propensity score methods and multivariable regression were used to account for confounders
• Deliveries were stratified by indication – dystocia or fetal distress

RESULTS:

• 10,901 deliveries: 5,057 attempted midcavity operative vaginal or caesarean deliveries with dystocia and 5,844 attempted midcavity operative vaginal or caesarean deliveries with fetal distress
• Rate of severe perinatal morbidity/mortality was 1.42% (dystocia) and 2.34% (fetal distress)
• The rate of severe maternal morbidity was 1.03% in both groups

Dystocia Indication

• ‘Attempted’ midcavity operative vaginal delivery was associated with higher rates of severe perinatal morbidity/mortality compared with caesarean
  • Forceps: Adjusted rate ratio (ARR) 2.11, 95% CI 1.46–3.07
  • Vacuum: ARR 2.71, 95% CI 1.49–3.15
  • Sequential: ARR 4.68, 95% CI 3.33–6.58
• Midcavity operative vaginal delivery was associated with higher maternal morbidity/mortality compared to cesarean
• Forceps: ARR 1.57, 95% CI 1.05–2.36
• Vacuum ARR 2.29, 95% CI 1.57–3.36

Fetal Distress Indication

• ‘Attempted’ midcavity vacuum delivery was associated with higher rates of severe perinatal morbidity/mortality compared with caesarean (ARR 1.28, 95% CI 1.04–1.61)
• ‘Attempted’ midcavity forceps delivery was associated with increased severe maternal morbidity compared to cesarean following (ARR 2.34, 95% CI 1.54–3.56)

CONCLUSION:

• Attempted midcavity operative vaginal delivery is associated with higher rates of severe morbidity/mortality and severe maternal morbidity, dependent on indication and instrument
• Maternal morbidity was mainly related to higher rates of postpartum hemorrhage
• Obstetric and birth trauma rates were increased 2.8- to 8.5-fold following attempted vacuum delivery and forceps depending on indication and instrument
• Authors recognize major limitation is non-experimental design
  • RCTs may not be feasible

Learn More – Primary Sources:

Perinatal and maternal morbidity and mortality among term singletons following midcavity operative vaginal delivery versus caesarean delivery

Related ObG Topics:

Does Presence of Senior Obstetricians Impact Mode of Delivery?

Operative Vaginal Delivery or Repeat Cesarean Section During Trial of Labor

Does BMI Impact Success of Vacuum-Assisted Vaginal Delivery?

Vacuum Delivery – What is the Better Training Approach?