Introducion: Few studies to date have shown the adverse effects of prolonged latent phase. Related factors, maternal and fetal outcomes of prolonged latent phase were studied in order to prevent these effects. Methods: In a cross-sectional study, 224 women were assessed at Shohada hospital by using questionnaire, examination and follow up to calculate the latent phase duration up to 3cm dilatation. Results: Of the total, 22.8% had prolonged latent phase and there was no difference in the maternal and fetal age/weight, gravid and parity. 41.2% were nulipars. None of the cases had delivery trauma, but 4 out of 7 meconium aspirated cases, 2 out of 6 hospital admissions, and both the 2 cases admitted in NICU were in prolonged latent phase group. None of the infants in this group had APGAR less than 8. There was no significant difference between APGAR<6 and meconium aspiration cases in the two groups. Massive post partum bleeding, cesarean section, and fever during/after delivery showed a significant difference. Other variables didn’t show any significant difference. Parity had a direct correlation in the normal group and indirect correlation in theprolonged latent phase duration group. Conclusion: Maternal age and weight, gravid, parity, infantile weight, gender and gestational age have no effect on latent phase duration. The more the parity, the more prolonged the latent phase and this leads to more cases of cesarean section, fever during/after delivery and post-partum bleeding.