Sudden crying of newborns may be caused by physiological factors such as hunger and fright, or it may be considered to be caused by intestinal spasms, vitamin D deficiency rickets and other diseases. 1. Physiological factors: because newborns can not speak, when there is hunger, as well as the situation of being frightened, newborns will suddenly cry. This kind of situation is usually normal, no need to worry. 2. Intestinal spasm: the cause of intestinal spasm is not yet clear, may be due to allergies, environmental stimuli and other factors. When the child has paroxysmal acute abdominal pain, it may be accompanied by crying. 3. Vitamin D deficiency rickets: It is caused by vitamin D deficiency, leading to abnormal calcium and phosphorus metabolism, thus affecting bone growth and calcification. Its etiology is related to perinatal vitamin D insufficiency, preterm delivery, insufficient sunlight and other factors. Affected children may present with symptoms such as excessive sweating, easy to scare, irritability, etc. Some of them show sudden crying. There are many causes of sudden crying in newborns. Parents are advised to bring their children to a regular hospital to find out the cause of the disease.