Two-month-old babies suddenly cry in their sleep, which may be related to hunger, environment, calcium deficiency and so on. 1. Hunger: the baby may not have eaten enough to go to sleep, hunger can cause crying, generally give the baby after feeding the baby do not rush to put the child down, you can gently burp, make sure the baby ate enough to go to sleep again. 2. environment: too hot or too cold will cause the baby to feel uncomfortable, or the surrounding environment is empty baby lack of security, may cause the baby to sleep suddenly cry. 3. Calcium deficiency: two months of the baby if calcium deficiency, may also lead to the above situation, but also accompanied by excessive sweating, occipital baldness and other aspects of the phenomenon. The two-month-old baby sleep suddenly crying, there may be 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’s treatment.