If your child suffers from an aversion to food, or if the primary constipation is accompanied by fever, vomiting, blood in the stool, weight loss or pain during bowel movements, it is good seek medical attention. However, the most important thing is to see a doctor if the infant's constipation persists for several months. Long-lasting constipation can be caused by chronic problems, such as celiac disease or other congenital disorders of the digestive tract.