Breastfeeding protects against malnutrition and growth failure in children with microcephaly associated with congenital Zika syndrome.

Congenital Zika Virus Syndrome (CZS) impacts children's physical and cognitive development, and it is still unknown how breastfeeding protects their growth. This 5-year cohort study followed children with CZS microcephaly to analyze the relationship between breastfeeding practices and the presence of malnutrition and growth failure at 6, 24, 36, 48 and 60 months. Breastfeeding was evaluated by Exclusive breastfeeding (EBF) under six months, EBF for the first two days after birth (EBF2D), long-term EBF (LTEBF, when above 3 months), short-term EBF (STEBF, when below 3 months), and continued breastfeeding 12-24 months (CBF). Malnutrition was determined by z-scores weight-for-age, length/height-for-age, and weight-for-length/height, and the presence of growth failure. Associations were explored using covariate-adjusted logistic regression equations. Malnutrition increased throughout childhood. The LTEBF reduced the risk of underweight and stunting at 24 months simultaneously (RR = 0.163; 95% CI = 0.03-0.996; p = 0.049); and children who received CBF had a lower risk of growth failure between 6 and 24 months (RR = 0.034; 95% CI = 0.0-0.52; p = 0.015). Breast milk was a protective factor against malnutrition for children with CZS, reducing the risk of underweight and stunting at 24 months and the risk of growth failure between 6 and 24 months.