Baby sleep patterns vary by age, but in general, the average baby gets about 15 hours of sleep per day. While most of this sleep should occur at night, it is quite common for newborns to mix up their nights and days so that they are wide awake most of the night. This should change by about six weeks of age, when the circadian rhythm that most adults abide by is adopted by the baby, as well. Babies only have two sleep states, and are generally easier to wake than adults are. Additionally, their sleep cycles tend to be shorter, as most wake up about every hour, and then either return to sleep or stay up.
Newborn babies sleep the most, as they are expected to sleep up to 18 hours each day, waking up about every two to four hours to eat. By six months old, baby sleep patterns change in that the sleep time decreases to about 12 hours per night with two naps in the day, and the baby should be able to sleep through the night without waking up to eat. At one year old, a baby typically sleeps for ten hours at night with two naps during the day, with only one nap per day being needed when he is 18 months old. Of course, baby sleep patterns vary, as some babies sleep for a long time at once, while others tend to cat nap throughout the day.
Adults experience several sleep stages, including deep sleep and REM sleep, while baby sleep patterns only encompass active and quiet sleep. Though babies do not technically have REM sleep, the active stage is similar for them, as their eyelids flutter, their breathing is irregular, and they occasionally cry out. Like adults in REM sleep, babies in the active stage of sleep wake up easily, though if they are not woken up, they should continue into the quiet stage. During this time, they have regular breathing, no eyelid flutters, and very little body movement. They are less likely to be woken up during quiet sleep, which is why this is the stage when SIDS can occur.
The entire sleep cycle for adults takes up to 100 minutes, while the sleep cycle for babies only lasts up to 60 minutes. After this hour, babies usually either wake up to eat, or go right back to sleep to begin the cycle again. Baby sleep patterns are usually better established by six months of age, when they begin to experience NREM, or non-rapid eye movement sleep. Though this shows progression toward an adult sleep pattern, the sleep cycle of a baby does not usually reach 100 minutes, as this typically only occurs when a child begins attending school.