Most babies start sleeping longer stretches at night around 3 to 4 months old, with many sleeping five to six uninterrupted hours by 6 months. But “sleeping through the night” doesn’t mean what most new parents think it does. In pediatric terms, it means six consecutive hours, not eight or ten. Your baby may also wake briefly during those stretches and fall back to sleep on their own.
What Happens in the First 8 Weeks
Newborns aren’t biologically equipped for long nighttime sleep. Their stomachs hold roughly 20 mL at birth, about four teaspoons, which empties in about an hour when fed breast milk. That tiny capacity drives the frequent feeding-and-sleeping cycles that define the first weeks. As your baby grows and their stomach expands, they can take in more at each feeding and go longer between them.
There’s also a brain maturation piece. A baby’s internal clock doesn’t function at birth. The sleep-related circadian rhythm doesn’t reach a meaningful pattern until after about day 56, or roughly 8 weeks. Before that point, babies have no biological distinction between day and night. Around 6 to 7 weeks, melatonin production starts to kick in at sunset, which is the first sign that your baby’s body is learning the difference between light and dark. Initially, sleep timing is driven purely by light exposure, but it gradually shifts to follow the household’s schedule.
The 3 to 6 Month Window
This is when most families notice real progress. Some babies begin sleeping six-hour stretches as early as 3 months. By 4 months, a good number have reached that milestone, and by 6 months, most babies can manage five to six hours without needing a feeding. That doesn’t mean every baby will. The range is wide, and “most” still leaves plenty of babies who take longer.
A few things come together in this window. Your baby’s stomach is now large enough to hold a feeding that sustains them for several hours. Their circadian rhythm is established, so their body produces sleep-promoting hormones on a predictable schedule. And their sleep cycles, which are shorter than adult cycles, start to mature in a way that allows them to link one cycle to the next without fully waking up. That ability to briefly rouse between cycles and drift back to sleep, sometimes called self-soothing, is the real skill behind “sleeping through the night.”
How Much Sleep Babies Actually Need
Babies between 4 and 12 months need 12 to 16 hours of total sleep per 24-hour period, including naps. Falling below 12 hours consistently is considered insufficient for healthy development. Within that range, there’s a lot of normal variation. A 5-month-old might sleep 10 hours at night with three naps, while another sleeps 11 hours at night with two naps. Both can be perfectly fine.
As nighttime stretches get longer, daytime naps gradually consolidate too. Most babies drop from three naps to two somewhere around 6 to 8 months, and from two naps to one between 12 and 18 months. Night sleep and nap schedules influence each other, so a baby who naps too late in the afternoon may resist bedtime, and a baby who doesn’t nap enough may be overtired and sleep worse at night.
Breastfed vs. Formula-Fed Babies
Exclusively breastfed babies under 6 months wake more often at night than formula-fed babies. This is consistent across studies. Breast milk digests faster than formula, so breastfed infants get hungry sooner. That said, the total amount of nighttime sleep is roughly the same for both groups in those early months. The difference is in how often sleep gets interrupted, not how much sleep the baby gets overall.
After 6 months, the gap becomes more noticeable. Breastfed babies tend to sleep somewhat less at night and over the full 24-hour day compared to formula-fed babies. This doesn’t mean breastfeeding causes sleep problems. Breastfed babies often nurse for comfort as well as hunger, and nighttime nursing helps maintain milk supply. If you’re breastfeeding and wondering whether your baby’s waking pattern is normal, it probably is, even if it looks different from a formula-fed baby’s schedule.
Sleep Regressions Are Normal Setbacks
Just when you think you’ve turned a corner, your baby may start waking more again. These regressions typically last two to four weeks and are tied to whatever your baby is going through developmentally, not to a specific calendar age. Common triggers include learning a new physical skill like rolling over or pulling up (babies literally want to practice at 2 a.m.), growth spurts that create extra hunger, teething pain, illness, and separation anxiety, which tends to peak around 9 months.
Most babies experience at least one regression in their first year. Some go through several. The pattern usually resolves on its own once the underlying developmental shift settles. The key is that regressions are temporary disruptions to a pattern that was already established, not a sign that something has gone wrong.
Bedtime Routines Make a Measurable Difference
One of the most actionable things you can do is establish a consistent bedtime routine. Research on young children found that a nightly routine led to significant reductions in both how long it took kids to fall asleep and how often and how long they woke during the night. The improvements showed up within three weeks. A control group with no routine saw no change over the same period. Mothers in the routine group also reported feeling better about their child’s sleep overall.
The routine itself doesn’t need to be elaborate. A predictable sequence of bath, feeding, story or song, and lights out gives your baby cues that sleep is coming. Consistency matters more than the specific activities. Starting this early, even at 6 to 8 weeks when the circadian rhythm is just forming, helps your baby associate certain cues with nighttime sleep. Over time, those associations become powerful tools for falling asleep independently and returning to sleep after brief nighttime wakings.
A Realistic Timeline
Here’s a rough map of what to expect, keeping in mind that every baby’s trajectory is different:
- 0 to 6 weeks: Sleep comes in 1 to 3 hour bursts around the clock. No circadian rhythm yet. Night and day look the same.
- 6 to 8 weeks: Melatonin production begins. You may notice slightly longer stretches at night, maybe 3 to 4 hours.
- 3 to 4 months: Some babies start sleeping 5 to 6 hour stretches. Sleep cycles begin maturing, though the 4-month mark is also a common time for a regression.
- 5 to 6 months: Most babies can sleep 5 to 6 hours without feeding. Self-soothing ability improves.
- 6 to 12 months: Nighttime sleep continues to consolidate. Many babies sleep 8 to 10 hours with zero or one feeding. Regressions around 8 to 10 months are common due to separation anxiety and mobility milestones.
If your baby doesn’t match this timeline, that doesn’t necessarily signal a problem. Babies who were born preterm, who are smaller, or who are going through a developmental leap may take longer. The overall trend matters more than any single week.