The causes of nine-month-old babies waking up frequently at night include improper parental care, vitamin D deficiency and gastrointestinal disorders, etc., which need to be promptly investigated and treated as soon as possible. 1. Improper parental care: Due to the low indoor temperature, parents did not give more covers in time, or the baby’s sleeping environment is too bright, etc., which interferes with the nine-month-old baby’s normal sleep and shows the above symptoms. It is recommended to eliminate the triggering factors in time to improve the quality of sleep. 2. Vitamin D deficiency: it is easy to lead to the reduction of calcium synthesis, nervous system dysfunction, the baby may show the symptoms of frequent night waking. 3. Gastrointestinal tract dysfunction: Because the nine-month-old baby digestive system is not yet fully developed, a variety of adverse factors are likely to lead to indigestion or gastroenteritis and other gastrointestinal tract dysfunction, showing abdominal distension, abdominal pain, etc., affecting the normal sleep. Nine-month-old babies waking up frequently at night may also be related to other causes, it is recommended to consult a doctor in order to clarify the cause of the disease, standardized treatment.