Birth weight is a measure commonly used to assess circumstances at childbirth. This study had the objective of analyzing the connection between birth weight and maternal variables according to Certificates of Live Birth. The design was transversal, descriptive, analytical, and the sample was formed by 4015 birth certificates from Maringa Municipality, Parana, Brazil, in the year 2001. Prevalence of low birth weight was of 7.6%. The variables that show significant association with low birth weight are the following: parity, 50.11% of women were giving birth for the first time (x2 =18.01)? female newborn (x2=3.98);number of prenatal check ups < 7 check ups (x2= 74.49); prematurity (x2= 1357.97) and normal delivery (x2 =12.80). The study of Certificates of Live Birth variables is an instrument of vital importance for planning actions targeting both mothers and children’s health.