The word is misleading. A sleep regression looks like a step backwards: your baby is waking hourly again, naps shrink to 20 minutes, falling asleep takes forever. But inside your baby's head, the opposite of a setback is happening. The brain is remodeling.
Around the 4 month mark, for example, sleep architecture matures: your baby trades newborn sleep for real sleep cycles with light and deep stages, the same kind you have. Between cycles they surface briefly, and that is new and unsettling for them. Later regressions come with developmental leaps: crawling, separation anxiety, first steps, first words. The brain practices at night what it learned during the day.
That's why experienced parents eventually land on the same reframe: regression is progression. Your baby isn't sleeping worse because something is broken. They're sleeping worse because a whole lot is going right. You didn't cause this, and there is nothing you need to fix.
Not every baby goes through every phase, and the ages are ballpark figures, not appointments. But the patterns repeat in most children with surprising reliability:
| Age | What's behind it | Duration (typical) |
|---|---|---|
| Around 4 months | Sleep cycles mature, sleep architecture gets rebuilt | 2-4 weeks |
| Around 6 months | Starting solids, new mobility, first attempts at rolling | 1-3 weeks |
| 8-10 months | Crawling, pulling up, separation anxiety kicks in | 2-4 weeks |
| Around 12 months | First steps, dropping from two naps to one | 1-3 weeks |
| Around 18 months | Autonomy phase, strong will, separation anxiety | 2-4 weeks |
| Around 2 years | Language burst, first nightmares, often the move to a big bed | 1-3 weeks |
The most important part of that table is the right-hand column: a sleep regression usually lasts 2 to 4 weeks, then sleep settles back in at the new developmental stage. Our tip, half serious, half survival strategy: write down the date it started. In 2 to 4 weeks, you'll exhale.
And yes, the parent community is right with its favorite joke: it ends, and then at some point the next phase shows up. Which is exactly why it pays to understand the pattern once. The second time around you'll know: this is a leap, not a crash.
Because every phase has its own trigger, it helps to know them individually. That way you can place what's happening faster and see where it's heading.
The 4 month sleep regression is the only one that brings something permanent: your baby switches from newborn sleep to real sleep cycles with light stages where they briefly wake. This new sleep architecture stays; over the following weeks your baby simply learns to handle it. That's why it feels like the toughest one to most parents.
The 6 month sleep regression often coincides with starting solids and first rolling. The gut is processing something new, the body wants to move, and both land at night. It's usually shorter than the 4 month one.
The 8 month sleep regression (often anywhere from 8 to 10 months) is a movement-and-attachment phase: crawling, pulling up and the onset of separation anxiety make sleep restless. Your baby practices new skills at night and seeks more closeness at the same time.
The 12 month sleep regression tends to hang on first steps and the shift from two naps to one. The midday nap reshuffles, and until the rhythm settles, night sleep is briefly scrambled.
The 18 month sleep regression is a head thing: your toddler discovers their own will, separation anxiety returns, and bedtime turns into a negotiation. Calm and familiar rituals carry you further here than any argument.
The 2 year sleep regression is the last of the bunch: language explodes, first nightmares appear, and often the move from crib to big bed is due. It passes too, usually within a few weeks.
Every regression any baby has ever had came to an end. This one will too. Coffee helps in the meantime.
You don't need to launch a new program mid-regression, and you don't need to pick a method off the internet. Keep the rhythm roughly as it was: similar times, similar steps, familiar rituals. That gives the remodeling brain a frame to hold on to. Keep an eye on wake windows, because an overtired baby turns any regression into an encore.
The rest is expectation management: lower the bar for nights, for the household and for yourself. Accept help, split the nights if there are two of you. You are not doing anything wrong. There is nothing to win in this phase except getting through it, and that is entirely enough.
In the middle of a regression, every night feels equally bad. Darli shows you the timeline: when it started, what is shifting right now, and the first nights that are calming down again. The date you meant to write down is already there.
The prediction rides out the phase with you. Darli adapts to your baby's new rhythm instead of insisting on the old one. One tap when they wake, one tap when they fall asleep, Darli sorts the rest.
Sleep, feeds, diapers: one tap is enough. Darli sorts the rest.
The best known one arrives around the 4 month mark, with more typically following around 6, 8 to 10, 12 and 18 months, plus one more around the second year. The ages are ballpark figures: not every baby goes through every phase, and the timing shifts from child to child.
Usually 2 to 4 weeks, and some phases are over after a week or so. Once the brain has processed the developmental step, sleep settles back in at the new level. If it drags on much longer, or comes with fever, pain or loss of appetite, talk to your pediatrician.
By the sudden break: a baby who slept reliably starts waking noticeably more often, fights naps or takes much longer to fall asleep. The break often lines up with a visible developmental step, like rolling, crawling or first steps.
Because it isn't a temporary glitch but a permanent upgrade: your baby switches to real sleep cycles with light stages where they briefly surface. This new sleep architecture is here to stay. That sounds scarier than it is, because over the following weeks your baby learns to link those cycles on their own.
No. A regression is not a verdict on how you do bedtime, and it doesn't demand a new method. Whether you ever change anything is your family's call, on your timeline. For the phase itself, keeping familiar routines roughly in place and offering the closeness your baby is asking for is enough. Habits that sneak in usually fade out again on their own.
Yes. Around the second year another phase often shows up: language takes a leap, the first nightmares appear, and the move from crib to a big bed is frequently due. It usually lasts only one to three weeks and settles once your child gets used to the change.
No, and you shouldn't. Exhausted parents need fewer jobs, not more. With Darli, one tap at sleep and one at wake-up is enough; the app sorts the timeline, the start date and the first better nights for you. It's the reminder that this passes, not another item on your to-do list.
This guide is not a substitute for medical advice. If you are worried about your child, talk to your pediatrician or midwife.
