Nine-month-old children suddenly crying in their sleep may be due to nightmares, mosquito bites and other reasons, and may also be due to intestinal cramps, high fever and other causes of disease. 1. Physiological factors: the nine-month-old suddenly cried out in his sleep, may be due to nightmares, resulting in a sense of fear. It may also be due to pain, itching and other discomfort caused by mosquito bites, which can also cause the nine-month-old to cry in his sleep. 2. intestinal spasm: nine months the child sleep crying may also be feeding too fast, or low temperature and other factors, resulting in intestinal wall smooth muscle spasm, pain, abdominal distension and other symptoms. 3. High fever: nine-month-olds may have a rise in body temperature due to a variety of factors such as exposure to cold and viral infections. If the body temperature is high and not hydrated in time as well as other treatment measures, it can lead to muscle spasms and pain, triggering the child to cry. Nine-month-old children suddenly cry in their sleep may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.