The duration of breastfeeding after the introduction of another milk in child feeding was studied, by following a cohort of mothers and their infants during one year. Daily information about breastfeeding, introduction of non maternal milk, besides other events concerning the child, were registered by the mother in a specially formatted sheet, with a 60-day "capacity". Trained interviewers visited the mothers at infant ages of 15, 30, 60, 90, 180, 270 and 360 days to return and replace the sheets. Four hundred and fifty children provided valid information to be included in the analysis. Survival analysis techniques were used to describe and to compare the duration of breastfeeding after the introduction of non maternal milk. Fifty four (12.0%) infants never received non maternal milk during the observation period; 193 (43,0%) received non maternal milk within the first sixty days of birth (group 1), 151 (33.5%) started receiving non maternal milk between sixty one and one hundred and eighty days (group 2) and 52 (11,5%) thereafter (group 3). The median times of duration of breastfeeding after the introduction were, respectively, 76, 120 and 176 days. Taking the first group as the base category, the hazards ratio of the second group was 0.73 (IC: 0.57-0.94) and 0.43 (IC: 0.26-0.72) for the third group. It was concluded that the earlier the introduction of non maternal milk the faster the process of weaning, and that mothers intending to breastfeed their children for a large period do it delaying the introduction of non maternal milk, and maintaining both breastfeeding and non maternal milk after the introduction, for as long as possible.
Breastfeeding; Non-maternal milk; Weaning; Cohort