Malpresentations--impact on mode of delivery.

Fetal malpresentation, including persistent occipitoposterior position, is a major cause of dystocia resulting in obstetric interventions. We studied malpresentation among 11 957 consecutive singleton deliveries from 1995 to 2004. There were 1 030 deliveries with a malpresentation (8.6%). Cephalic malpresentations occurred in 5.4% of deliveries (persistent occipitoposterior 5.2%, face 0.1%, brow 0.14%), and 3.1% had breech presentation and 0.12% a transverse lie. The odds ratios (OR) for cesarean section were 14.89 (95%CI 11.91-18.63) in breech presentation and 4.57 (95% CI 3.85-5.42) in persistent occipitoposterior presentation. With persistent occipitoposterior position, the OR for instrumental vaginal delivery was 3.84 (95%CI 3.14-4.70). Primiparity was associated with increased malpresentation risks, as 54.6% of those with malpresentations were primiparous compared with 41.7% of those without (OR 1.68, 95%CI 1.48-1.91, p < 0.001). Primiparous women required more cesarean sections (OR 1.92, 95%CI 1.50-2.47) and instrumental deliveries (OR 2.89, 95%CI 1.50-2.47). Malpresentation frequently leads to cesarean section or instrumental delivery, especially among primiparous women.