A one-month-old baby a day without defecation may be a normal phenomenon, may also be an abnormal phenomenon, need to be based on the baby’s specific circumstances and continue to observe the baby defecation to determine. 1. One-month-old babies gastrointestinal function development is not perfect, defecation is not regular, a day without defecation is normal, more than three days belongs to constipation, according to the cause is divided into functional constipation and organic constipation, need to find the cause in a timely manner, to give the corresponding treatment. 2. Functional constipation, mostly caused by indigestion, improper diet and other factors, can be given to adjust the diet, digestion and other ways to improve. 3. organic constipation, such as congenital megacolon, intestinal obstruction and other diseases, need to go to the hospital in time to improve the abdominal ultrasound and other relevant examination, clear cause, give symptomatic treatment. Therefore, a month-old baby did not poop for a day, it is recommended to seek medical treatment, by the judgment of a professional physician to deal with.