Introduction and object: This study was designed for determining the birth weight and some other factors affecting rural newborn children in the north of Iran (south east of Caspian sea). Material and Method: A sample size of 695 cases was chosen by cluster and random sampling from 20 villages. The birth weight of the newborn and the mother's socioeconomic status were recorded by a questionnaire. The data was analyzed by SPSS windows software. Results: The prevalence of LBW, NBW and HBW was observed to be 11.1%, 84.1% and 4.8%, respectively. The birth weight among children whose mothers had iron supplements was lower than that of children whose mothers did not take iron supplement (3173gr vs 3246gr) and statistical differences between the two groups were not significant. Birth weight have a positive correlation and significant statistical differences with both maternal age (r=0.2 , p=0.01) and maternal BMI(r=0.24 , p=0.01). The birth weight in the 5th birth order was more than that in the 1st birth order and statistical differences were significant (P=0.01). Birth weight had a positive correlation with familial income (P<0.05). Discussion: Our study showed that maternal BMI, birth order and socioeconomic factors were associated with intrauterine weight gain, but iron supplements didn't have a positive outcome
