Background and Aim: Low weight at birth is one of the main health indexes in evaluating pregnancy period care, and recognizing its related factors is very important. The aim of this study was a comparison of pregnancy age, height, the distance between two pregnancies, gaining weight during pregnancy, economical condition, nutrition, general health of the mothers with low and normal birth weight.

Materials and Methods: The research method was casual-comparative conducted as field-work. From all newborns born since (Jan 2008 to Nov 2009) 168 low birth weight babies with their mother and 157 newborns with normal weight from 20 maternity center at Guilan province were randomly selected. Mothers filled general health questionnaire with the reliability of 0.82. The data were analyzed using SPSS Software.

Results: There was a significant difference among mothers (case and control ) in terms of pregnancy age, height ,distance between two pregnancies, increasing weight during pregnancy, economical condition, nutrition condition and general health (mental), (p0.01).

Conclusion: Various factors affected newborns' weight at birth. Therefore, decreasing the rate of low weight will be one of the main social health indexes requiring cooperation of counter- groups and different organizations such as the Ministry of Health and treatment, psychotherapy, counseling centers and radio/television.