The Four Month Sleep Regression: What Every Parent Needs to Know

There is perhaps no more exhausting moment in early parenthood than this: your baby has finally found a rhythm. Nights are becoming more predictable, stretches of sleep are growing longer, and you are starting to feel like yourself again. Then, seemingly overnight, everything changes. Your baby is waking every hour, refusing to settle, and napping for only minutes at a time. If this sounds familiar, you may be in the thick of the four month sleep regression.

The good news is that you are not doing anything wrong. What your baby is going through is a completely normal and even exciting developmental shift. In this post, we will explain exactly what the four month sleep regression is, why it happens, what you can expect, and how to support both your baby and yourself through it.

What Is the Four Month Sleep Regression?

The term "sleep regression" can feel alarming, as though your baby is moving backwards. In reality, the opposite is true. Around three to five months of age, your baby's sleep architecture permanently matures from the simple two stage newborn sleep pattern into a more complex, adult like cycle with four distinct stages, including light sleep, deep sleep, and REM sleep.

As a newborn, your baby spent roughly equal time in light and deep sleep and moved quickly into deep restorative sleep after closing their eyes. Now, as their brain develops, they cycle through lighter stages of sleep more frequently throughout the night. Sleep cycles at this age last approximately 60 to 120 minutes, and at the end of each cycle, your baby naturally surfaces into a lighter state of awareness. If they have not yet developed the ability to settle back to sleep on their own, they will call out for you.

This is why sleep experts often say that the four month sleep regression is the only true regression that is permanent. It does not go away because it is not a phase: it is a developmental milestone. Once babies learn to link sleep cycles independently, the night waking typically improves significantly.

Signs Your Baby Is Going Through the Four Month Sleep Regression

Every baby is different, but the most common signs include frequent night waking (sometimes every 60 to 90 minutes), shorter naps that seem to end just as your baby is about to reach deep sleep, difficulty falling asleep at the start of the night, increased fussiness or clinginess during the day, and a larger appetite due to extra energy expenditure. Some parents also notice that their baby seems more interested in the world around them and harder to settle in bright or stimulating environments.

Not every baby will show all of these signs, and not every baby will experience the transition as dramatically. Some babies sail through with minimal disruption, while others go through several weeks of disrupted sleep. Both are entirely normal.

Understanding Wake Windows at Four Months

One of the most effective tools for navigating this stage is paying close attention to your baby's wake windows, which are the stretches of awake time your baby can comfortably manage between sleeps. At four months, the recommended wake windows are roughly 90 to 120 minutes. The first wake window of the day tends to be around 90 minutes, the middle of the day windows sit around 100 to 110 minutes, and the final wake window before bedtime can stretch to approximately 120 minutes.

Getting wake windows right matters more than it might seem. An overtired baby finds it harder to fall asleep and stay asleep because the body releases cortisol to fight fatigue, which is stimulating rather than calming. Conversely, an undertired baby simply will not be ready to sleep. Watching your baby's sleepy cues closely and aiming for a consistent daily schedule helps regulate their internal clock and reduces the likelihood of bedtime battles.

Creating a Calming Bedtime Routine

Even at four months, babies are beginning to recognise patterns and sequences. Research suggests that babies can start responding to consistent routines as early as 8 to 12 weeks of age. A simple, predictable bedtime routine signals to your baby's nervous system that sleep is coming, helping to ease the transition from wakefulness to rest.

A good routine does not need to be complicated. Something like a warm bath, a gentle massage, a feed, a lullaby or soft music, and then placing your baby in their cot works beautifully. Keep the routine to around 30 minutes and try to do the same steps in the same order each night. Consistency is more powerful than any particular activity you choose.

Setting Up a Safe Sleep Environment

Creating a safe and sleep friendly environment is one of the most important things you can do for your baby. European safe sleep guidelines recommend that babies sleep on their back, on a firm and flat surface, in a room that is kept between 16 and 20 degrees Celsius. The cot or bassinet should be free of loose bedding, pillows, bumper pads, and soft toys. The only items that belong in the sleep space are a firm mattress and a tightly fitted sheet.

Room sharing for at least the first six months is recommended by health organisations across the Netherlands, Belgium, Germany, and Scandinavia, as it significantly reduces the risk of Sudden Infant Death Syndrome (SIDS). However, bed sharing is not advised, as it carries its own safety risks.

A dark room also makes a meaningful difference. Blackout blinds can help your baby distinguish day from night and encourage longer, more restorative sleep. White noise can mimic the comforting sounds your baby knew from life in the womb. Setting up a dedicated, consistent sleep space in a quality cot is an investment that pays dividends night after night.

The HelloLoomi Baby Crib ELIN with Mattress provides a beautiful, sturdy foundation for safe sleep from newborn through toddler years, giving you peace of mind from the very first night.

The Swaddle Transition at Four Months

Swaddling can be a powerful tool in the early weeks, helping newborns feel secure and reducing the startle reflex that often wakes them. However, by the time the four month sleep regression arrives, many babies are beginning to show signs of wanting to roll, and at this stage, swaddling must stop.

Safe sleep guidelines are clear: as soon as your baby shows any interest in rolling from back to tummy, swaddling is no longer safe. A swaddled baby who manages to roll onto their front cannot use their arms to reposition themselves, which presents a serious suffocation risk.

The transition away from swaddling can feel daunting, especially right in the middle of a sleep regression. Moving to a sleeping bag or gradually transitioning one arm out at a time can help your baby adjust gently. In the weeks before this transition becomes necessary, a quality swaddle wrap gives your baby the cosy, contained feeling that supports healthy early sleep.

The HelloLoomi Baby Swaddle with Bear Ears is designed with your baby's comfort and safety in mind, crafted from soft breathable fabrics that keep your baby snug without overheating, making it a favourite for parents from Amsterdam to Oslo.

Gentle Approaches to Help Your Baby Through the Regression

There is no single right method for helping your baby through this phase, and most sleep experts agree that formal sleep training before six months is generally not recommended. What you can do in the meantime is begin gently laying the groundwork for independent sleep.

One of the most useful habits to start now is placing your baby in their cot drowsy but awake, rather than fully asleep. This way, your baby learns to associate their cot with the sensation of drifting off, rather than only connecting sleep with being held, rocked, or fed. When they wake briefly between sleep cycles, they have a better chance of recognising their environment and settling back without needing your help.

If your baby becomes distressed, responding promptly and warmly is always appropriate at this age. Gentle techniques such as patting, shushing, or briefly picking up and settling before placing back down are all reasonable approaches. The goal at four months is not to leave your baby to cry but to gradually help them build the capacity to self soothe over time.

During particularly unsettled periods, a gentle baby swing can offer invaluable support. The rhythmic motion can help calm an overstimulated baby and ease the transition into sleep.

The HelloLoomi BaBi Baby Swing provides a gentle, soothing rocking motion in a beautifully crafted indoor swing that fits naturally into any nursery and can make a real difference during those long, wakeful evenings.

Taking Care of Yourself During This Phase

It is easy to focus entirely on your baby's sleep while neglecting your own. Sleep deprivation is genuinely hard, and it is important to acknowledge that. If you have a partner, take turns responding to night wakings so that each of you gets at least one solid stretch of sleep. Accept help when it is offered, lower your expectations for productivity during the day, and remind yourself that this is a phase with a beginning, a middle, and an end.

Connecting with other parents in your community, whether in the Netherlands, Belgium, Germany, or across Scandinavia, can also make a significant difference. Knowing that other families are navigating the same exhausting nights is genuinely reassuring, and often these conversations lead to practical tips that no parenting book ever quite captures.

When to Talk to Your Doctor

Most of what happens during the four month sleep regression is completely typical. However, it is always worth speaking to your paediatrician or family doctor if your baby seems to be in pain, is not gaining weight well, has a significantly reduced appetite alongside the sleep disruption, or if you have any concerns about their overall health and development. Ear infections, growth spurts, and other health factors can sometimes amplify sleep difficulties and are worth ruling out.

The Light at the End of the Tunnel

The four month sleep regression is temporary in its intensity, even if the underlying sleep architecture change is permanent. Once your baby builds the ability to link sleep cycles, nights typically begin to improve. Many families find that around six months, with a consistent bedtime routine in place, their baby begins to settle more reliably and wake less frequently through the night.

You are not failing if your baby is not sleeping through the night. You are navigating one of the most demanding developmental transitions of infancy, and doing so with love and attentiveness. Trust the process, lean on your support network, and know that better nights are ahead.

At HelloLoomi, we are here to support you through every stage of your baby's first years with thoughtfully designed products that genuinely make a difference. Explore our full range of nursery and sleep essentials to help create a warm, safe, and soothing sleep environment for your little one.

Frequently Asked Questions

Why did my baby suddenly start waking up every hour at four months?

Around four months, your baby's sleep architecture permanently shifts from the simple two stage newborn pattern to a more complex cycle with multiple stages, including light sleep, deep sleep, and REM sleep. At the end of each cycle (roughly every 60 to 90 minutes), your baby briefly surfaces into lighter sleep and may wake fully if they have not yet learned to settle independently. This is the four month sleep regression, and it is a sign of healthy brain development rather than a problem with your parenting.

How long does the four month sleep regression last?

The acute phase of increased waking and disrupted naps typically lasts two to four weeks, though every baby is different. Some families see improvement sooner, while others take a little longer. The underlying change to your baby's sleep cycles is permanent, but once babies develop the ability to self soothe and link sleep cycles, the frequent night waking generally resolves and sleep improves significantly.

Is it safe to swaddle my baby during the four month sleep regression?

You should stop swaddling as soon as your baby shows any signs of attempting to roll from back to tummy, which often begins around two to three months and is common by four months. A swaddled baby who rolls onto their front cannot use their arms to reposition themselves, which presents a safety risk. Transitioning to a sleeping bag or moving one arm free at a time is the recommended approach at this stage.

What wake windows should I use for a four month old baby?

At four months, aim for wake windows of approximately 90 to 120 minutes between sleeps. The first wake window of the day is usually around 90 minutes, the middle of the day windows sit at roughly 100 to 110 minutes, and the final wake window before bedtime can extend to around 120 minutes. Keeping wake windows age appropriate helps prevent overtiredness and supports more settled sleep at night.

What room temperature is safest for a sleeping baby in Europe?

European health guidelines recommend keeping your baby's room between 16 and 20 degrees Celsius for safe sleep. This range reduces the risk of overheating, which is a known risk factor for Sudden Infant Death Syndrome. Check the back of your baby's neck rather than their hands or feet to assess whether they are at a comfortable temperature, and dress them in breathable layers suited to the room.

Can I start sleep training during the four month sleep regression?

Most paediatric sleep experts recommend waiting until at least six months before beginning formal sleep training. However, you can begin laying gentle groundwork now by placing your baby down drowsy but awake and establishing a consistent bedtime routine. These habits help your baby start to associate their cot with the feeling of falling asleep, which can make more structured sleep training easier and more effective when you are ready to try it.

What HelloLoomi products can help my baby sleep better?

Several HelloLoomi products are designed to support healthy, safe infant sleep. A quality swaddle like the HelloLoomi Baby Swaddle with Bear Ears provides secure, breathable comfort for newborns and young babies before the rolling transition. The HelloLoomi BaBi Baby Swing offers gentle rhythmic motion to help calm and settle overtired babies. The HelloLoomi Baby Crib ELIN with Mattress provides a sturdy, safe sleep surface from birth through toddlerhood.