Occipital posterior and occipital transverse positions: reappraisal of the obstetric risks

Malpositions in labour in a vertex-presenting fetus are known to be associated with increased risks of operative delivery A retrospective analysis of all deliveries over 4 years in a university teaching obstetric unit was performed using the available obstetric database. All cases of live births with cephalic presenting babies after 36 completed gestational weeks were analysed, and included 17,533 out of 20,533 total deliveries over the study period. The study group included those cases with occipital posterior and transverse positions, based on the documentation of the position of the vertex at the time of delivery, or at the last clinical examination before obstetric intervention, while occipital anterior cases constituted the control group. The overall incidence of malpositions was 14%, and operative delivery rate in the study group was 82.5% versus 20.7% in the control group. After excluding cases of operative delivery for non-mechanical indications, such as fetal distress, the adjusted odds ratio for the malposition group was 9.8 (95% CI 8.91-10.8) for total assisted delivery and 30.2 (95% CI 25.6-35.5) for Caesarean section compared to the occipital anterior group. Malpositions are definitely associated with a marked increase in the risk of operative delivery including Caesarean section. Labour complicated by malposition should be considered high risk, and should warrant due preparation for obstetric intervention.