What's the baby passing stool normally before this? Often it has been seen that the child may have one I'm perfect imperfecta Din us which was missed by the pediatrician during birth. So the child is unable to defecate. However constipation is not very uncommon because only breastfeeding does not provides enough roughage for the child to pass stools. I would advise you to give glycerine suppositories via anus which will smooth and his rectum and allow the child to pass stool easily.