Background: Birth weight has been shown to be influenced by numerous factors including, maternal characteristics such as maternal BMI. In pregnancy, there is increased adipose tissue which can cause to maternal obesity and insulin resistance. There is visfatin expression increase specific to pregnancy. Aim: We planned this study to assess relationships of the first trimester maternal BMI with new-born anthropometric characteristics and visfatin levels throughout pregnancy. Methods and Material: This longitudinal, observational study on 100 nulliparous pregnant women carried out in Birjand, Iran, over three trimesters in 2016. The researcher asked the participants to fill out the Researcher-made questionnaire including demographic and anthropometric characteristics including first trimester BMI and then referred them to laboratory to serum sample taking from mothers and visfatin levels measurement in the three trimesters. Neonate’s anthropometric measures (weight, height, head circumference) and sex of new-borns were obtained from hospital reports. Results: Pearson correlation test indicated significant correlation between birth weight and the first trimester maternal BMI (r= 0.27, P=0.02). Also, Spearman’s correlation test showed a weak negative correlation between head circumference with mean visfatin level (r= -0.23, P=0.04). Linear regression showed that birth weight predicts 28% of variation of BMI. Also, there was significant difference between the maternal level of education and the mean of birth weight (P=0.027). Conclusions: Results of the present study showed that the mean of birth weight was comparable with capital cities in Iran, it is necessary to strengthen the existing mother and child health care program and to develop new approaches.