Objective: studying the prevalence of low birth weight (LBW), preterm birth (PTB) and intrauterine growth restriction (IUGR), their associated maternal factors and this particular population's aetiology in the Bolivariana teaching hospital's Maternal and Infant Protection and Attention Unit in Medellin (Unidad de Proteccion y Atencion Materno Infantil de la Clinica Universitaria Bolivariana). Methodology: a retrospective cross - sectional study analysing data regarding 2,672 mother - offspring pairs registered in the Perinatal Information System from May 5th 2003 to March 30th 2006. This sample represented 45% of the deliveries which occurred during this period. Results: LBW prevalence was 17%, preterm delivery 21% and IUGR 12%. Inadequate prenatal care, smoking during gestation and any type of maternal pathology present during pregnancy were associated with LBW. Conclusion: identifying maternal factors associated with the LBW of their offspring will help to implement public health interventions aimed at preventing unfavourable offspring outcomes in the population at risk. Subsequent studies should be made from a population - based perspective at national level to generalise the results.