81-day-old babies do not poop for three days may be too little water intake, gastrointestinal tract is not fully developed and other physiological factors, but also may be indigestion, congenital megacolon and other diseases caused. 1. Physiological factors: if the child has too little water intake in daily life, it will lead to slow peristalsis of the gastrointestinal tract, which will lead to the phenomenon of not pooping. In addition. There is also the possibility that the 81-day baby is in the developmental period, the gastrointestinal tract is not yet fully developed, so the phenomenon of not pooping for 3 days. 2. Dyspepsia: The causes of dyspepsia mainly include gastrointestinal dyskinesia and other factors. The main symptoms of the affected children are postprandial fullness, middle and upper abdominal pain, constipation and so on, so 81 days the baby will appear 3 days without pooping symptoms. 3. Congenital megacolon: congenital megacolon is due to genetic inheritance and environmental factors, children will have persistent constipation, abdominal distension and other manifestations. Therefore, 81 days baby will appear 3 days without poop phenomenon. 81 days baby 3 days do not poop, there may also be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.