There is no particularly strict definition of how long a full-term baby sleeps a day, usually 16 to 20 hours, are normal. Full-term babies usually do not have a diurnal pattern in their sleep and sleep most of the day, and it is normal for them to sleep 16 to 20 hours a day. Usually, babies wake up once after 4 to 5 hours of sleep, during which time they usually eat, defecate or play, etc. However, if a full-term baby sleeps a lot, it is normal for the baby to sleep for 16 to 20 hours a day. However, if a full-term baby often sleeps for too short or too long, this is usually not normal. For example, if your baby sleeps less than 15 hours a day or more than 22 hours a day, it is recommended that you seek medical attention to clarify whether there is any abnormality. Full-term babies sleep for about 16 to 20 hours. It is recommended that babies sleep in a quiet, warm and dimly lit environment. If you have any questions about feeding, it is recommended that you consult a pediatrician.