PURPOSE: to check the association between oral dysfunction and socioeconomic factors, variables related to the mother and to the newborn as well breastfeeding performance during the first 48 hours of life. METHODS: a cross-sectional study, analytical, carried out at a public maternity of Recife (PE - Brazil). All mothers of full-term newborns were attended between April and July 2008, totaling 588 mother/infant pairs. The assessment of the oral motor sensory system of the child and breastfeeding performance were developed, coded as a zero when the item was "expected / normal" and one where "not expected and risk." The total sum of the items "not expected and risk" resulted in an Index of Oral Dysfunction and an Index of Breastfeeding Performance. RESULTS: it was found that 57.3% of the mother/infant pairs had change of feeding, 43.9% had 1 and/or 2 changes and 13.4% greater number of changes. The frequency of oral dysfunction was approximately 30%. In logistic regression analysis among the included variables, just the oral dysfunction remained significantly associated with the failure of breastfeeding. Children with many changes in oral function showed a 4 times greater chance to get feeding alteration. CONCLUSIONS: oral dysfunction is one of the causes for non-establishment of lactation, and should be identified early, as it may be corrected, thereby avoiding weaning. The maternity staff should be trained in breastfeeding management, with a healthcare professional that offers special care for abnormalities in the oral motor sensory system.