The examined risk indicators of dystocia were: dilatation and consistency of cervix, thickness of lower segment, descent of fetal head and fetal head-to-cervix contact at admission to the delivery ward, infertility prior to current pregnancy and use of epidural analgesia. Measurements of lower uterine segment, cervix and fetal head conditions were performed manually during routine vaginal examinations. In the pilot phase of the study two methods of validation of vaginal examinations were considered: use of a model or an additional examination by a second midwife. Both methods were discarded as constituting an unacceptable extra workload and also, in the case of the latter, for ethical reasons. We assumed that the weight of the expected child plays a role in the progress of labour. However, the actual weight of the expected child is unknown and cannot with accuracy be taken into consideration for potential clinical management of the labour. Our analyses included as well as excluded, respectively, birth weight in the regression model to examine the effect of birth weight on the clinical risk indicators.