Lactancia materna y protección contra las infecciones respiratorias en los primeros meses de vida

background: the protective role against respiratory infections is included among the advantages of breastfeeding (bf). objective: to describe the pattern of bf in a cohort of newborns and its protective role against respiratory infections (ri) in the infant. material and methods: a cohort of 316 newborns (nb) from madrid health districts 8 and 9 was followed by telephone calls every fortnight during the winter season recording clinical and epidemiological data. nasopharyngeal aspirate was obtained in every patient with symptoms compatible with ri. results: one thousand, eight hundred and sixty-five phone calls [median: 4.2 (1-11)], and 106 scheduled visits were conducted. at the age of 1 month 56.1% of the infants were exclusively breastfed, at 3 months 39.4% and at 5 months 31.9%. the duration of bf was 65.1 days (sd: 43.49) and no factors were associated to a longer duration. eighty nine acute ri were registered. the presence of siblings in school age increased the risk of ri by 1.74 (ci 95%: 1.12-2.72) in all the strata of duration of exclusive bf. the risk of ri increased by 5 (ci 95%: 2.07-12.19) if breastfeeding lasted less than 1 month, by 9,8 (ci 95%: 4,06-23,66) between 30-60 days and by 3,4 (ci 95%: 1.28-9,19) if it lasted 60-90 days. conclusions: though many nb begin bf, only a third part of them go on with it at the age of 5 months. no covariant was associated with a longer duration. bf is a protector factor against ri when it lasts more than 90 days. so it must be promoted specially in those infants with siblings in school age.