The   preterm   birth  is one of the  main  health problems and the most

   common   cause  of  prenatal   and  neonatal  death. The  objective of this

   study was to determine the prevalence of preterm birth and its risk factors.

         We conducted  cross-sectional study with 1087 sample of networks who

   were the   total of  births of Babol for three months in three hospital in 1998.

   The   data were  collected  by  determining gestational age using LMP and

   interviewing  with  mothers. We  used  multiple  logistic regression analysis to

   estimate the standardized relative risk(RR).

         The   result   showed  the  prevalence  of  preterm birth was 9% with 95%

   confidence  interval (7.3% , 10.7%). The risk of  preterm  birth  was increased

   2.71 times significantly among women with hypertension during pregnancy

   (P<0.01). The relative risk was 2.64 folds (P<0.05) among twins and 1.75 folds

   (P<0.05) among women with a history of abortion. The risk  of  preterm birth

   was decreased in private hospital(RR=0.58,P<0.05). In the stepwise multiple

   logistic regression  analysis  only  the   effect  of hypertension in pregnancy

   (RR=3.35, P<0.01) and being twin (OR=2.64, P<0.05) and having a history of

   abortion (RR=1.80, P<0.05) significantly  increased  the  risk  of preterm birth

   and among  private  hospital  (OR=0.57, P<0.05) , the  risk  was  decreased

   significantly.

         Therefore , with   eliminating  the  obstacle  of  prenatal   care and with

   creating health services, the surveillance system  should  perform  especial

   care  in  high  risk   pregnancies , especially ,  for  women  with  a  history of

   abortion , and hypertension and twin gestation. Thus surveillance program,

   continuing education , consultation and coordination between clinics and

   health centers contribute prevent the preterm birth.