OBJECTIVE To measure the prevalence of modifiable risk factors for the nursing diagnosis of risk of sudden infant death syndrome (RSIDS), and to establish the association between the prevalence found and the sociodemographic characteristics of the sample. MATERIAL AND METHODS The sample was composed of 384 mothers (Spaniards, Moroccans and Ecuadorians). Data were collected in the maternity ward of Sta. M del Rosell Hospital in Cartagena (Murcia) from June to November 2007 through a questionnaire containing items on sociodemographic variables and questions about upbringing habits and practices, which are defined as modifiable risk factors by the NANDA-I taxonomy. In the statistical analysis, the Chi-square test was used for qualitative variables and Student's t-test and analysis of variance were used for quantitative variables. RESULTS A total of 77.1% of newborns were diagnosed with RSIDS related to modifiable risk factors. Notable was the high prevalence of risk factors such as the choice of side-lying position to put the newborn to bed in 39.8% (153) and smoking during pregnancy in 25.7% (99). Statistically significant associations were found (p<0.001) between the diagnosis of RSIDS and the mother's nationality, educational level and household income. CONCLUSION The high prevalence of some modifiable risk factors among newborns raises the need to provide more information about upbringing habits and practices for SIDS prevention, not only in Infant Nursing Consulting Rooms but also throughout pregnancy and in the first days of life of the newborn.