[Factors associated with cross-nursing]

This article aims to estimate the prevalence and analyze the factors associated with cross-nursing. A cross-sectional study was conducted in 2013 with interviews with a representative sample of mothers of infants less than one-year-old (n' = 695) attended in nine primary health units in Rio de Janeiro, Brazil. Sociodemographic characteristics were studied; pregnancy, childbirth and primary care assistance; maternal habits and baby features. Adjusted prevalence ratios (PR) were obtained by Poisson Regression, retaining variables associated with the outcome in the final model (p ≤ 0.05). Cross-nursing was practiced by 29.4% of the mothers. Most practitioner mothers were relatives or friends. The following variables were directly associated with cross-nursing: being an adolescent mother (PR' = 1.595), smoking (PR' = 1.396), alcohol consumption (PR' = 1.613), inappropriate baby feeding habits (PR' = 1.371) and infant's age in months (PR' = 1.066). Maternal formal employment was inversely associated with the practice (PR' = 0.579). Cross-nursing has a relevant prevalence among mothers assisted by primary health care units in Rio de Janeiro City. This issue should be addressed, especially among the most vulnerable groups, due to the association with adolescence and with unhealthy habits.