Effect of rotation on perineal lacerations in forceps-assisted vaginal deliveries

To determine the difference in the rates of severe perineal lacerations between forceps-assisted vaginal deliveries in the occiput-posterior position compared with forceps-assisted vaginal deliveries in which the fetal head was rotated to occiput-anterior before delivery.

We studied a retrospective cohort of 148 women who had a forceps-assisted vaginal delivery from 2008 to 2011 at the University of Pittsburgh. Mild perineal lacerations were defined as first or second degree, and severe lacerations were defined as third or fourth degree. χ and t tests were used for bivariate and logistic regression was used for multivariable analyses. P<.05 was considered statistically significant.

Of 148 forceps-assisted deliveries, 81 delivered occiput-anterior after either manual or forceps rotation, 10 delivered in the occiput-posterior or occiput-transverse position after an unsuccessful rotation, and 57 delivered occiput-posterior without attempted rotation. No significant differences were found among demographic, obstetric, and neonatal characteristics of the groups. Overall, 86 (67.7%) women had mild lacerations and 41 (32.3%) had severe lacerations. A significantly greater rate of severe perineal lacerations was found in the occiput-posterior nonrotated compared with the rotated group (43.4% compared with 24.3%; P=.02). In multivariable analyses, adjusted for age, race, insurance, body mass index, gestational age, parity, episiotomy, and birth weight, forceps-assisted vaginal delivery in the occiput-posterior position without rotation remained significantly more likely to be associated with severe lacerations (odds ratio 3.67, 95% confidence interval 1.42-9.47).

Forceps-assisted vaginal delivery after rotation of an occiput-posterior position to an occiput-anterior position is associated with less severe maternal perineal trauma than forceps-assisted delivery in the occiput-posterior position.

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