By the fourth month, most babies have started to differentiate between day and night, and to sleep for longer stretches of time during the night. In fact, by 4 months, some babies can sleep through the night, and most babies manage a 5-hour stretch by 6 months. During this period, the American Academy of Pediatrics recommends that babies sleep between 12 and 16 hours in every 24-hour period, naps included, on a regular basis, for normal growth and best health.
Babies around this age usually get around 3 to 4 of those hours of sleep during the day for naps. These naps can be more frequent, and as short as a half hour, but more often are an hour to an hour and a half long, two to three times a day. This leaves around 8 to 12 hours of sleep during the night. Those 8 to 12 hours are usually interrupted by feeding during the night, although some babies may go the entire 12 hours without a feeding.
During this time, babies' sleep patterns become more regular and predictable, and being able to recognize these patterns is an important first step towards being able to alter them until they better fit the whole family's sleep needs.
While many babies can differentiate between day and night by their fourth month, a few are differentiating in the wrong direction. For babies who like to sleep all day and party all night, it may take a little extra effort to help their sleep schedules settle into normal, healthy routines. Day-night reversals can happen for many reasons, from the fact that many babies in the womb sleep during the day, when they’re rocked by the motion of their mothers walking around and going about their day, to the fact that, for many babies of working parents, night can seem like the most exciting time of day - the time when their favorite people are home.
No matter what the reason for a day-night reversal, if it’s getting in the way of the family managing a full and restful night’s sleep, it may be time to work on adjusting your baby’s understanding of her circadian rhythms. Making sure she spends some time in the sun or natural light during the day, and keeping your home relatively dimly lit in the evening, can help kickstart her body’s natural hormonal responses to night and day. In addition, keeping quiet and refraining from playing with her when she wakes up during the night can take away some of the appeal of being up during the darker parts of the day.
One thing to avoid, though, in trying to change a child’s day-night reversal, is trying to keep her up during the day so that she’ll stay up during the night. Limiting daytime sleep can sometimes make nighttime sleep harder, since over-tiredness can actually make it harder for babies to fall asleep. On the other hand, it can be helpful to limit daytime naps to no longer than 2 hours, to make the difference between napping and bedtime more obvious.
your baby is growing more mobile every day, but even if she is starting to roll over on her own, she is still safest if she is put to bed lying on her back, on a firm mattress with a tightly fitted sheet, and with no pillows, blankets, or soft toys in it. Around this time, your baby might start to roll over on her own during the night, and that’s nothing to worry about - if she is moving herself into new positions, it’s a pretty good sign that she has the muscle control to stay in them safety, or move into a different one if necessary.
your baby’s increased mobility also means that if you’ve been swaddling her previously, but she's started rolling, it's now time to stop swaddling. Swaddling can create a great sense of security for newborns, but as those newborns grow into older infants, the way the swaddle can interfere with movement can make sleep less safe. In addition, tight swaddling beyond 3 months of age can interfere with hip development and has been associated with developmental hip dysplasia. If your baby likes to be in a snug environment to sleep, or if you want to keep her nice and warm, you can buy a sleep sack (a safe wearable blanket) that is loose enough to allow for movement, including safe rolling.