Population and methods - All cases of confirmed NEC matched to controls for identical gestational age and period of hospitalization; apnoeas-bradycardias prospectively counted. Results - Forty-five cases were compared to 89 controls. The isolated risk factors were: an intra-uterine growth retardation (OR = 3,65, 95% confidence interval {CI} 95%: 1,54-8,63); a birth weight < 1000 g (OR = 8,16, CI 95%: 1,17-56,62), compared to a weight greater than or equal to 1500 g; a triple antibiotherapy (OR = 6,15, CI 95%: 1,16-32,45); an umbilical venous catheterization (OR = 2,64, CI 95%: 1,09-6,44); a number of simple apnoeas-bradycardias greater than or equal to 3rd tercile (n = 27) (OR = 4,54, CI 95%: 1,29-15,93), or severe (stimulated or with hypoxia) apnoeas-bradycardias 3rd tercile (n = 8) (OR = 6,15, CI 95%: 1,59-23,75); an haemoglobin level lower than the 1(st) tercile (95 g/L) (OR = 5,90, CI 95%: 1,20-20,13); and milk thickening by Gumilk((R)) (OR = 2,78, CI 95%: 1,11-6,90). Conclusion - In the present practices, anoxo-ischemic factors during the first week of life do not represent an important risk of NEC; a great vigilance must be exercised for indications of the triple antibiotherapy and the treatment of apnoeas-bradycardias. (C) 2003 Editions scientifiques et medicales Elsevier SAS. All rights reserved.