OBJECTIVE:To establish and test the effectiveness of a low-risk scoring system to predict obstetric outcome for the selection of women suitable for confinement in low-intervention units. METHODS:Retrospective analyses were performed on data from 2900 women enrolled in the Western Australian Pregnancy Cohort Study and 1353 women managed at a midwifery-based birth center. A combination of the principal predictors of obstetric outcome, incorporating a previously published scoring system and various clinical features, was used to exclude high-risk cases at 18 weeks' and 36 weeks' gestation. Stepwise multivariate logistic regression analyses of the remaining pregnancies then produced a low-risk scoring system. RESULTS:This system predicted a 55% chance of an uncomplicated delivery in a midwifery-based setting after allocating 54% of women to the low-risk category. It predicted an 82% chance of an uncomplicated delivery in a primary medical care setting with the allocation of 84% of women as low risk. CONCLUSION:The results of this study suggest that adding induction and augmentation of labor, together with low pelvic instrumental delivery, to the treatment options in a low-intervention unit would raise the rate of successful confinement within the unit from 55% to 82%. Our scoring system now requires prospective evaluation to further assess its clinical value.