Four-month-old babies always love to sleep can be seen in physiological phenomena, disease states (such as intracranial infection, severe pneumonia), whether it is normal need to be combined with the baby’s situation to determine the specific, such as the age of the baby’s mental response is good, no abnormal symptoms, it is normal. 1. Physiological phenomenon: for four-month-old babies, sleep time is usually longer, up to 14-16 hours a day, such babies in general (such as the spirit, response and feeding) are good, and no obvious abnormal symptoms (such as fever, convulsions, etc.), so such babies always love to sleep is a normal physiological phenomenon. 2. Disease state: (1) intracranial infection: such as severe viral encephalitis, the baby may appear sleepy, manifested as “always sleepy”, poor mental response and poor breastfeeding, at the same time, there may be fever, convulsions or vomiting and other symptoms, improve the lumbar puncture and cranial magnetic resonance imaging can assist in the diagnosis. (2) Severe pneumonia: These babies may also have the above symptoms, with poor mental response, fever, respiratory distress, etc. In severe cases, cardiopulmonary failure may occur, and may even be life-threatening. It is recommended to go to the hospital in time for a comprehensive judgment and evaluation by a specialist.