OBJECTIVE: To investigate covariates that could affect the variation in mean length/age z scores in the first year of life of children born full term with normal birth weight. METHODS: This was a prospective study of a cohort of mother-infant pairs recruited at public maternity units in two municipalities in the Brazilian state of Bahia, from March 2005 to October 2006. This paper reports the results for linear growth of 489 children who were followed-up for the first 12 months of their lives. A mixed-effect regression model was used to investigate the influence of covariates of mean length/age z score during the first year of life. RESULTS: The multivariate mixed effect analysis indicated that mothers not cohabiting with a partner (β = 0.2347; p = 0.004) and increased duration of exclusive breastfeeding (β = 0.0031; p < 0.001) had a positive impact, whereas mother’s height less than 150 cm (β = -0.4393; p < 0.001), birth weight of 2,500-2,999 g (β = -0.8084; p < 0.001) and anemia in the child (β = -0.0875; p < 0.001) all had a negative impact on the variation in estimated length/age z score. CONCLUSIONS: Therefore, the results of this study indicate that short maternal stature, birth weight < 3,000 g and anemia in the infant had a negative effect on linear growth during the first year of life, whereas longer duration exclusive breastfeeding and mothers who did not cohabit with a partner had a positive effect.
Infant growth; predictors; mixed effect models; cohort study
