28 days baby 3 days without stool may be a normal physiological phenomenon, can also be seen in functional constipation, congenital megacolon, hypothyroidism, etc., the specific need to analyze and determine the cause. 1. Physiological factors: 28-day baby 3 days without stool, if the milk, good spirit, no bloating and other discomforts, usually is a normal physiological phenomenon, generally do not need too much intervention. 2. Functional constipation: for 28 days 3 days without stool, there may be a prolonged interval between defecation than the daily interval, part of the stool can be accompanied by dryness affecting defecation, mostly belongs to the functional constipation. 3. Congenital megacolon: clinical persistent constipation, may appear the above phenomenon, often have a history of delayed expulsion of fetal stool, the baby can be due to the different length of the lesion intestinal tube may have different clinical manifestations, the lesion is serious constipation time early and constipation symptoms are serious, some of the baby may appear vomiting, abdominal distension and other symptoms, improve the abdominal X-ray examination can assist in the diagnosis. 28 days old baby 3 days no stool may also have other reasons, such as hypothyroidism, etc., it is recommended to go to the hospital in a timely manner, improve the examination to determine the cause of the disease, to give targeted treatment or treatment.