Background and Objectives: Folic acid is a B vitamin which 5mg daily intake before gestation and until the tenth week of pregnancy is recommended. Since no study has been conducted in some regions of East Azerbaijan including Bostanabad, Khosroshahr and Sarab and no prevalence was spotted in country specific studies, therefore, the aim of this study was to determine the relationship between folic acid intake and infant birth weight.

Material and Methods: This study was a retrospective cohort. In this study, 1939 of pregnant women who were referred to health care centers before pregnancy were selected randomly. They were divided into two groups: first group of pregnant women who regularly took folic acid before pregnancy and second group included the women who did not take folic acid supplements. Data were analyzed by SPSS 16 using T-Test and ANOVA.

Results: This study was conducted on 1939 mothers who had an average age of 25.98 years and average infants birth weight was 3.209 kg. Totally, 92.9% of the mothers had regular consumption of folic acid during pregnancy. Analysis of the results showed that with increasing maternal BMI, birth weight also increased. It showed a significant relationship between regular folic acid intake and increase in infant birth weight.

Conclusion: Our results showed that both high maternal pre-pregnancy weight and folic acid intake lead to higher birth weight infants.