Objective. To investigate the feasibility of an objective assessment of the progress of preterm labor at different gestational ages. Subjects and methods. This prospective, nonrandomized study comprised 150 women with premature births at various gestational ages and 50 control women with full-term births. The study estimated and differentiated objective factors for predicting preterm labor within 24 hours. Results. Based on the discriminant analysis, the predictive significance of various parameters for predicting preterm labor was estimated depending on the gestational age. The risk of childbirth with extensor presentation of the fetal head is established in very early, early and preterm labor. Conclusion. To assess the risk of preterm labor, ultrasonic measurements of cervical vascularization index and the fetal headñ perineum distance need to be done in addition to routine diagnostic evaluation. In very early, early and premature labor with the extensor presentation of the fetal head, the risks of vaginal birth should be considered together with a neonatologist. © Bionika Media Ltd.