1-year-old baby suddenly crying in the middle of the night may be related to mental excitement, improper feeding, lack of vitamin D and other factors. 1. Mental excitement: if the baby mood during the day is more excited or frightened, resulting in the baby’s brain nervous system to appear excited, so that the baby nightmares at night to be frightened, there may be a 1-year-old baby suddenly crying in the middle of the night. 2. Improper feeding: if because of improper feeding, may lead to the baby indigestion, abdominal distension and abdominal pain phenomenon, so may make the 1-year-old baby suddenly cry in the middle of the night. 3. lack of vitamin D: vitamin D can promote the absorption of calcium, the lack of vitamin D leads to calcium deficiency, may lead to the baby appeared nerve excitability enhancement, appeared irritable and restless as well as not down to earth and other symptoms, so the lack of vitamin D may lead to a 1 year old baby suddenly cried in the middle of the night phenomenon. 1 year old baby suddenly crying in the middle of the night may also have other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.