Babies crying in their sleep may be caused by personal factors, environmental factors, and also may be related to problems such as hypocalcemia. 1. Personal factors, if the baby is hungry, urine may lead to physical discomfort, so there will be symptoms of sleep crying. 2. Environmental factors, if the baby is often in a high or low temperature environment, the light is too bright, the environment is too noisy may affect the baby’s sleep, so the baby may appear to cry in bed. 3. Hypocalcemia, part of the infant sleep crying may also be related to the lack of calcium in the body, due to the occurrence of hypocalcemia may lead to a decline in the blood calcium content, the nervous system excitability increases, so this symptom will occur. Usually, we must pay attention to the baby’s physical conditioning, if there is any abnormality, we need to consult a doctor in time.