[Instrumental extractions using Thierry's spatulas: evaluation of the risk of perineal laceration according to occiput position in operative deliveries]. / Extraction instrumentale par spatules de Thierry: évaluation du risque périnéal en fonction du dégagement.

OBJECTIVE: Risk factors for severe perineal lacerations are nowadays well-known and they include operative vaginal deliveries and extractions in occiput posterior (OP) positions. The aim of this study was to assess whether OP position increases the risk for anal sphincter injury when compared with occiput anterior (OA) positions in operative deliveries using Thierry's spatulas. METHODS: Retrospective study of 163 extractions with Thierry's spatulas over a five-year period (January 2000 to December 2005) performed in a general hospital. Singleton cephalic pregnancies at term were studied and the incidence of severe perineal lacerations was noted in deliveries in OP and OA positions. RESULTS: In these 163 cases, the varieties of presentation obtained by vaginal examination were 129 in anterior and 34 in posterior positions. Eleven posterior positions rotated anteriorly on delivery and 23 remained in a posterior position. The OA group (n=140) and the OP group (n=23) were constituted. Anal sphincter injury occurred significantly more often in the OP group compared with the OA group (17.4% versus 2.9%, p=0.014) with an odds ratio of 7.1 (95% CI 1.6-31). Only one fourth-degree laceration was noted. Within the OP group, the incidence of vaginal lacerations was increased compared to the OA group, but without any significant difference (43.5% versus 27.9%, p=0.20). In a logistic regression model, the OP position was 6.4 times (95% CI 1.3-31.5) more likely to be associated with anal sphincter injury than OA position. The incidence of OP position was 14.1% within the whole population studied and Thierry's spatulas permit anterior rotations of occipito posterior presentation in only 32.4% of cases. CONCLUSION: The efficiency of Thierry's spatulas is proven. As with forceps and vacuum extractors, extraction with Thierry's spatulas is a risk factor for perineal laceration compared to a spontaneous delivery. In deliveries with spatulas, OP head positions further increase this perineal risk against OA positions. OP positions before fetal extractions do not seem to be an ideal situation for using spatulas, even if an anterior rotation is achieved in one-third of cases.