RESUMO
BACKGROUND: Prematurity is the most frequent cause of perinatal morbidity and mortality, and is responsible with 75% of neonantal deaths not related to congenital defects. OBJECTIVE: The aim of this study was to know risk factors that influence premature delivery in a third level attention in a Gyneco-Obstetric Unit. MATERIAL AND METHODS: In a case-control study, was conducted an interview with 300 mothers who had their delivery at 28 and 36 gestational weeks in group of cases and 600 mothers from 37 to 41 weeks in controls, who assisted for attention from April to September 2011. RESULTS: The factors associated eighth higher risk for prematurity were: maternal age above 35 years was more frequent in cases (14.6%), previous placenta occurred more frequent in cases (9.3%), Infectious disease were highly present in cases such as: urinary tract infection (46%). But association of 2 or more factors such as premature rupture of membranes and cervicovaginitis, were more frequent significantly in study group (76%). CONCLUSIONS: The prematurity risk factor more freqeunt were: infectouse disease in study group. A deficient prenatal attention can be increased in order to prevent premature delivery. When 2 or more factors associated in a gestation the risk also increase, and should increase the following and medical attention to reduce premature risk.