Objective: To compare perinatal outcomes between forceps- and vacuum-assisted deliveries. Our hypothesis was that the force vectors achieved in forceps delivery will lead to fewer shoulder dystocias, but greater perineal lacerations.
Methods: This was a retrospective cohort study of 4,120 term, cephalic, singleton, nonrotational operative vaginal deliveries at a single institution. Outcomes examined included rates of neonatal trauma, shoulder dystocia, and perineal lacerations. Potential confounders, including maternal age, birthweight, ethnicity, parity, station at delivery, episiotomy, attending physician, anesthesia, and length of labor, were controlled for using multivariate logistic regression.
Results: Among the 2,075 (50.4%) forceps- and 2,045 (49.6%) vacuum-assisted deliveries, the rate of shoulder dystocia was lower among women undergoing forceps delivery (1.5% compared with 3.5%, P < .001), as was the rate of cephalohematoma (4.5% compared with 14.8%, P < .001), whereas the rate of third- or fourth-degree perineal laceration was higher (36.9% compared with 26.8%, P < .001). These differences in perinatal complications persisted when controlling for the confounders listed above. The adjusted odds ratio for shoulder dystocia was 0.34 (95% confidence interval [CI] 0.20-0.57), for cephalohematoma was 0.25 (95% CI 0.19-0.33), and for third- or fourth-degree lacerations was 1.79 (95% CI 1.52-2.10) when comparing forceps to vacuum.
Conclusion: Vacuum-assisted vaginal birth is more often associated with shoulder dystocia and cephalohematoma. Forceps delivery is more often associated with third- and fourth-degree perineal lacerations. These differences in complications rates should be considered among other factors when determining the optimal mode of delivery.
Level of evidence: II-2.