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Introduction: Diagnosing parturients in risk of cesarean section early in the beginning of active phase of labor, is very important. This may let take necessary action to accelernate labor (delivery) and prevent maternal mortality and morbidity due to late cesarean section. Materials and Methods: During a period of 8 months from July 2004 to March 2005, 216 primiparous women, with term pregnancy and cephalic single fetus, referred to Imam Reza hospital in (during) active phase of labor, were studied. Changes of cervical dilatation and descent of the conceptus were observed. Parturients were devided to two groups, vaginal delivery and cesurean section. Protraction or arrest disorders were the indications of cesarean deliveries. Findings were analysed through using T-Test, unilateral variance and Chi square test. Results: The more changes in cervical dilatation in the first 2 hours of active phase of labor, the less possibility of cesarean delivery (p<0.001). Also the more rate of the conceptus descent in the first 2 hours of active phase of labor, the less rate of cesarean section (p<0.001). There was no significant statistical relationship between condition of membranes at the onset of active labor and method of delivery, however there was a significant relationship between oxytocin augmentation and method of delivery (p<0.001). Conclusion: In primiparous women with term pregnancy, vaginal delivery would be fairly predictable by observing changes of cervical dilatation and conceptus descent during the first 2 hours of active phase of labor.