Despite advances in obstetrics, prematurity is still a major public health problem because of the neonatal morbidity and mortality it causes. The objective of this study was to investigate maternal risk factorsfor premature births in a public maternity in the city of Imperatriz-MA. A cross-sectional comparative study was conducted with 116 mothers, through structured interviews. The data were analyzed using Epi-Info version 3.5.1. The variables that showed statistically significant association with preterm delivery were monthly income below two minimum wages (p = 0.046), stress during pregnancy (p = 0.027), primiparity (p = 0.044), absent or inadequate prenatal care (p <0.001) and clinical complications in pregnancy (p<0.001). The results show that the maternal risk factors implicated in prematurity are related mainly with lifestyle, socioeconomic and clinical variables, and prenatal care.