"When will my baby sleep through the night?" is one of the first questions every new parent asks. It's also one of the most misanswered, partly because nobody using the phrase means quite the same thing by it.
First, what does "sleeping through the night" actually mean?
There are three definitions floating around:
- The clinical definition: A continuous sleep stretch of 5–6 hours. By this measure, many babies "sleep through the night" by 3–4 months.
- The marketing definition (used by sleep books and forums): An 8-hour stretch from bedtime to morning. Around 6–9 months for most babies.
- The popular definition (what most parents mean): 12 hours straight from bedtime to morning, with no wake-ups. This is a smaller club. Many babies don't reach it until 9–12 months, and some not until well into the second year.
Knowing which definition you're working with matters. A pediatrician saying "she's sleeping through the night now!" at 4 months may mean (1), while a forum post is bragging about (3). Comparing those is comparing apples to a different fruit.
The biology, briefly
A few facts that change how you think about it:
Babies don't have circadian rhythms at birth. The day-night cycle that runs adult sleep is built up over the first 6–12 weeks. This is partly why newborn sleep is chaotic.
Sleep cycles in babies are shorter than in adults. A newborn's sleep cycle is about 50 minutes; an adult's is 90+. Babies pop into light sleep more often, which gives more opportunities to wake fully.
Stomach capacity drives early waking. Until around 3–4 months, a baby's stomach genuinely cannot hold enough to get through a 12-hour night. This isn't a sleep problem; it's anatomy.
The shift starts around 12–16 weeks. This is when most babies start consolidating night sleep into longer stretches. It's also when the "4-month sleep regression" famously hits, because sleep architecture is reorganizing.
What's typical at each age
Rough averages. Real babies vary widely.
| Age | Longest typical night stretch | "Sleeping through" odds (8+ hr) |
|---|---|---|
| 0–4 weeks | 2–3 hours | Effectively zero |
| 5–8 weeks | 3–4 hours | Very low |
| 9–12 weeks | 4–6 hours | Some babies |
| 3–4 months | 5–8 hours | Common |
| 5–6 months | 6–10 hours | Common |
| 7–9 months | 8–11 hours | Most babies |
| 10–12 months | 9–12 hours | Most babies |
| 12+ months | 10–12 hours | Most, with occasional wakings |
A few caveats:
- "Most babies" doesn't mean yours. The variation is enormous, and a baby who isn't sleeping through at 9 months isn't broken.
- Regressions happen. The 4-month, 8/9-month, and 12-month regressions are real phenomena that can temporarily undo months of progress.
- Illness, teething, travel, and developmental leaps reliably disrupt sleep.
What helps
There's a lot of marketing in baby sleep. The few things that genuinely move the needle:
1. Daytime sleep that isn't a disaster
Counterintuitively, well-rested babies sleep better at night. An overtired baby wakes up more often, in more upset states, and is harder to settle. The single biggest predictor of a good night isn't bedtime. It's whether the day was managed well.
This is why wake windows are useful. Hitting the bedtime window with a not-overtired baby gives you a much better shot at consolidated sleep.
2. A predictable bedtime routine
Even at 8 weeks, a 5–10 minute routine before sleep cues the body. Bath isn't required (and actually keeps some babies up). What matters is consistency:
- Dim the lights
- Diaper and pajamas
- A short feed
- Swaddle or sleep sack
- One song or short story
- Sound machine on
- Down to sleep
The same five steps in the same order, every night. It works because predictability calms the nervous system, not because of any particular activity.
3. A sleep environment that doesn't fight you
- Cool room (around 68–72°F / 20–22°C)
- Dark (blackout curtains genuinely help, even for daytime naps)
- Continuous white noise (loud enough to mask a flushed toilet from the next room)
- Safe sleep surface, no loose bedding
These small environmental changes are higher-leverage than most parents realize.
4. Letting the baby practice settling
This is the controversial one. Around 4–6 months, most babies can begin to learn to fall asleep without active rocking, bouncing, or feeding all the way to sleep. There are many ways to support this, ranging from gentle methods to more structured sleep training, and the choice is genuinely personal. The point is that some version of this skill, learned at some point, is part of what enables the long stretches at night.
A baby who needs you to actively put them back to sleep at every single light-sleep transition will wake fully more often. A baby who's practiced linking sleep cycles on their own will pop into light sleep just as often but not need you most of the time.
5. Dropping night feeds when the baby is ready
By 4–6 months, many (not all) babies no longer need calorie support overnight. Their stomachs hold enough, their daytime calories are growing, and their sleep architecture is mature enough.
Dropping night feeds is not the same as letting the baby cry. It can be done gradually:
- Slowly reduce the volume of bottle feeds at night, by half an ounce every few nights
- Shorten nursing sessions by a minute every few nights
- Eventually offer water instead, then nothing
By the end, the wake-up itself often disappears because the conditioned hunger isn't there.
If you log overnight feeds in Tottli during the wean-down, you'll see the volume curve drift down across two weeks before the wakeups disappear, which is a calmer signal than wondering each morning whether last night was "better."
This is a doctor-and-baby-specific question. Your pediatrician will tell you when night feeds aren't nutritionally necessary for your baby. Don't drop them on a schedule from the internet.
What doesn't help (or actually hurts)
A short list of things parents try that mostly don't pay off:
- Keeping the baby up later to "make them tired." Almost always backfires under 8 months. An overtired baby sleeps worse, not better.
- Adding more naps in hopes of better night sleep. Once the right number of naps is in place, more isn't more.
- Feeding to fullness right before sleep. Some pre-sleep top-off is fine; an oversized feed often produces gas and reflux that wakes the baby.
- Switching to formula "for better sleep." The research on this is much weaker than the lore. Formula-fed babies don't reliably sleep better than breastfed.
- Cereal in the bottle. Outdated advice, not safe, and not effective for sleep.
- Comparing to other babies. "My friend's baby was sleeping 12 hours by 8 weeks." Possibly true, possibly survivor-stat embellishment, irrelevant to your baby.
Regressions are real
Just when things start to feel okay, they often regress. The well-known ones:
- 4-month regression: sleep architecture matures and the previously-strong sleep often falls apart
- 8/9/10-month regression: developmental leaps + separation anxiety + mobility
- 12-month regression: sometimes related to nap transitions
- 18-month regression: language explosion, sometimes related to dropping the second nap
- 2-year regression: sometimes related to imagination/fears
Most last 2–6 weeks. The right move is usually to keep doing what was working, accept the temporary chaos, and not introduce new dependencies you'll need to undo later.
When to talk to your pediatrician
Most "not sleeping through" is just normal variability. A few patterns are worth raising:
- A baby past 6 months who has always needed feeding to settle, has dropped no night feeds, and is gaining weight unusually fast (overfeeding to sleep)
- Loud snoring or pauses in breathing during sleep
- Sleep that's getting noticeably worse over months (not regressions, but a steady decline)
- Daytime symptoms (sweating, choking, persistent reflux) interfering with sleep
- A baby who can't seem to settle at all, ever, with no methods working
Sleep that's "less than ideal" is not a medical problem. Sleep that signals a medical problem usually has other markers around it.
The honest headline
Most healthy babies sleep through the night (in some sense) somewhere between 4 and 12 months. There's a wide spread inside that and a small percentage of babies who lag for reasons that are not anyone's fault.
You can stack the deck (wake windows, environment, routine, gentle skill-building) and you'll likely shorten the path. You can't shortcut biology, and most of what people promise will get a young baby to sleep 12 hours straight is overpromising.
The phase ends. Often more abruptly than you'd expect. The baby who didn't sleep at 6 months is often a totally normal sleeper by 18 months and a great sleeper by 4. Hold the line, take care of yourself, and trade nights with whoever you can.