[Does persistent occiput posterior position increase the risk of severe perineal laceration?]

To assess the risk of severe perineal lacerations (III and IV degrees) during vaginal deliveries in occiput posterior position.

We conducted a retrospective cohort study of 9097 vaginal deliveries in a teaching hospital's maternity between January 1st 2005 and December 31st 2008. Risk factors associated with tears of the 3rd or 4th degree were studied by a multivariate logistic regression.

Severe perineal lacerations occurred in 1.69% of cases (n=152) and did not significantly vary between 2005 and 2008. Parity was a protective factor (OR 0.42; P<0.001; IC(95%) 0.29-0.60) whereas instrumental extraction was associated with an increased risk: vacuum (OR 3.95; P<0.001, IC(95%) 2.23-7.00) and forceps (OR 3.55; P<0.001, IC(95%) 2.33-5.42). macrosomia. Risks were also increased in fetal macrosomia and episiotomy did not protect the mother (respectively OR 1.41 P<0.001, IC(95%) 1.19-1.68 and OR 1.73; P<0.001, IC(95%) 1.16-2.57). Persistent occiput posterior position was not significantly associated with an anal sphincter injury (OR=1.70 P=0.059; IC(95%) 0.98-2.94).

In our series, occiput posterior position did not significantly impact the risk of severe perineal laceration. A manual rotation of the fetal head should be performed in case of associated risk factors.