3-year-old baby woke up at about 4:00 a.m., consider with the usual habits related, may also be calcium deficiency and other factors triggered. 1. living habits, if usually often give the baby drink too much water, may lead to the baby urine collection, so may appear around 4 am wake up symptoms, at the same time if often woke up around 4 am, the formation of the biological clock, may also appear this reaction. 2. Calcium deficiency, if the baby’s body calcium deficiency, may lead to elevated nervous system excitability, cerebral cortex over-excitement may affect the baby’s sleep, so this symptom will occur. 3-year-old baby woke up at about 4:00 a.m., there may also be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.