Introduction& Objective : Placenta previa is a serious complication of pregnancy and it is a considered an emergency in women's medicine, the aim of this study was to evaluate the incidence, risk factors pregnancies complicated by placenta previa.                                                           

Materials and methods :This is a retrospective study on patients files in Delivery branch of Valie Asr Hospital of Zanjan (1381-1383). The necessary information recorded in the questionnaires. 12834 pregnant women were assessed . Birth records of 93 cases with placenta previa and 940 randomly selected controls were reviewed retrospectively.Statistical analysis was performed using Pearson's Chi square Method. 

Results: Placenta previa  complicated 0.72% (n=93) of all deliveries included in the study (n=12834). Multiparity was more common in patients with placenta previa (P<0.001). Also the previous cesarean section, previous abortion  and previous placenta previa   more common in patients with placenta previa( P<0.0001). Placenta previa occurred in male infants  in 62 cases  (P<0.001).   Fetuses with placenta previa had lower fetal weight particularly, fetal weight less than 2500 g was a significant    ( P<0.0001).The newborns that were delivered after placenta previa graded lower Apgar scores less than 7 at 5 min (  P<0.0001) .    

Conclusion:   Multiparity , previous cesarean section, previous abortion and previous placenta previa are risk factors for placenta previa.