Background & Objectives: Birth weight less than 2500gr (as result of preterm delivery and/or intrauterine growth restriction (IUGR)) is a major cause of both neonatal health. Predominate cause of LBW in developed countries is premature birth, whereas in developing countries is more often IUGR. Different risk factors, including demographic and behavioral during and before pregnancy are effective in LBW incidences which can reduce LBW and neonatal mortality rate by identification and control of these risk factors. The present study has been carried out with purpose of identification and decreasing the LBW rate in Ardabil.

 Methods: In this case – control study all infants delivered in 2006 in hospitals in Ardabil were investigated. Every neonate whose weight was less than 2500gr was taken as a case (n=470) and 482 neonates whose weight was more than 2500gr was taken as a control. Data gathering was done through questionnaires, interviewing the mothers and physical examination. The data were analyzed statistically through SPSS.

 Results: In the present study, the presence of LBW amount is %6.4 in Ardabil hospitals. The results of our study showed that a significant relationship existed between prematurely and gestational age<37wk, mother’s age, mother’s job and maternal weight, premature rupture of membranes (PROM), maternal diseases, multiple births, bleeding during pregnancy, interval between pregnancies less than <2 years, prior history of low birth weight, use of drugs by mother in pregnancy, congenital malformation with LBW. In this study relation between parity, the use of Folic Acid, Fe, cigarette smoking and addiction of mother, living area (village or city), family marriage, health care and mother’s education were not significant with LBW.

  Conclusion: The LBW important risk factors in Ardabil hospitals were prematurity or gestational age <37wk, multiple pregnancies, PROM, mother’s age over 35 years, and mother weight <50kg, maternal diseases.