The 4-month sleep regression (which can start anywhere from 3 to 5 months) is a period when your baby's sleep suddenly becomes more disrupted. Babies who were sleeping longer stretches start waking frequently. Naps that were predictable fall apart. Bedtime becomes a battle.

This looks like: waking every 45 minutes to 2 hours at night, refusing to nap longer than 30 minutes, needing more help to fall asleep, or seeming overtired despite sleeping "enough" hours.

It feels like a cruel setback. But here's what makes this different from other sleep disruptions: this isn't actually a regression at all. It's a progression.

Around 3 to 5 months, your baby's sleep undergoes a permanent neurological shift. As a newborn, they had two simple sleep stages. Now, their sleep is maturing to include four distinct stages (light sleep, deep sleep, REM, and another light sleep), just like yours.

This is progress. But it also means they now fully wake between each sleep cycle instead of drifting smoothly from one to the next. Sleep cycles last about 45 to 60 minutes during the day and 60 to 90 minutes at night.

Think about your own sleep. You probably wake briefly between cycles, roll over, and drift back without remembering it. Your baby is learning to do this same thing, but they're brand new at it. If they've been falling asleep while feeding or rocking, they may need that same help every time they surface between cycles.

This is why a baby who was sleeping 4-hour stretches might suddenly wake every hour. They're waking briefly (which is normal), but they haven't yet learned how to get back to sleep on their own.

Their circadian rhythm is also developing around this time. Their body is trying to figure out when to be awake and when to sleep, and that internal reorganization makes everything feel more chaotic temporarily.

The adjustment period typically lasts 2 to 6 weeks. But how long varies widely based on your baby's temperament, what support they're getting, and factors you can't control (like developmental leaps happening simultaneously).

Some babies move through this transition relatively quickly. Others take longer. Neither means you're doing something wrong. If you're several weeks in and it feels endless, consider whether something else is happening. Growth spurts, new skills like rolling, or schedule issues can all compound the regression.

The goal isn't to "fix" your baby. It's to help everyone get through this phase as gently as possible. Here are approaches that help many families. Take what resonates, leave what doesn't.

Keep things predictable. Consistent routines help your baby's brain find its rhythm. Wake around the same time, keep bedtime sequences familiar, maintain nap routines.

Protect daytime sleep however you can. If naps fall apart, do what works temporarily. Contact naps, stroller walks, car rides. This isn't "creating bad habits." This is survival.

Feed well during the day. If your baby suddenly wakes constantly at night but seems uninterested during day feeds, they may be reverse cycling. Full, focused daytime feeds can help reduce nighttime hunger.

Give practice time during the day. Babies wake more during regressions because they're excited about new skills. Daytime practice means less midnight rehearsal.

Consider your own needs. If you're barely functioning, accept help and prioritize rest. Your wellbeing matters.

You'll read a lot about using this regression to teach independent sleep skills. If that's a goal for your family, this can be a time to start creating space for it.

But here's what often gets left out: you don't have to. Your baby is 4 months old. If feeding to sleep works, keep doing it. If co-sleeping feels right, that's valid. If contact naps are what everyone needs, that's okay.

The idea that babies "must" learn independent sleep now or they'll never sleep well is not true. Plenty of babies who continue being rocked, fed, or held to sleep at 4 months go on to sleep beautifully later.

What matters is finding an approach that feels sustainable for your family right now.

Stay consistent. Pick a response that feels sustainable and stick with it for 3 to 5 nights before deciding if it's working.

Don't create new dependencies out of panic. If feeding to sleep wasn't your pattern before, try not to start now. But if it was already your approach, don't feel pressured to stop.

Use supportive tools. Products like the Worm sleep companion can help your baby feel secure during the transition.

Remember this is temporary. The sleep cycle changes are permanent and healthy, but the intense disruption isn't.

The 4-month sleep regression is hard. But it's also a sign that your baby's brain is doing exactly what it's supposed to do. Their sleep is maturing, organizing, becoming more like yours.

You don't have to navigate this perfectly. You don't have to make all the "right" choices. You just have to get through it in whatever way works for your family, while trusting that your baby is developing normally.

The regression will pass. The sleep cycles will settle. And with the support that feels right for your family, your baby will move through this transition at their own pace.

The Worm Way is about trusting your intuition while understanding the science. Your baby is adjusting to a major developmental shift, and you're adjusting alongside them. That's hard work, and you're doing it. That's enough.