Baby Sleep Regression: When Does It Happen, How Long Does It Last, and What Can You Do?

Your baby was finally starting to sleep better, and then, almost overnight, everything changed. Suddenly, they're waking up several times a night, crying at bedtime, or taking shorter naps. This is commonly known as a sleep regression. It is often reported around 4 months, then again at 8 to 10 months, 12 months, 18 months, and 2 years. These periods are temporary and often last one to two weeks, although the duration varies from one child to another.

Here's what happens at each age, how long these unsettled periods can last, and what you can do to help your baby through them.

What Is a Sleep Regression?

“Sleep regression” is not a medical diagnosis. It's a common term used to describe a temporary change in a baby's sleep patterns, including more frequent night waking, difficulty falling asleep, shorter naps, and increased fussiness.

These periods often coincide with important developmental milestones, such as learning to roll over, crawl, pull themselves up, walk, or talk.

However, studies following large groups of babies have not found consistent sleep regressions at specific ages. A baby's sleep naturally varies from one night to another. If your child reaches these milestones without experiencing disrupted sleep, that's perfectly normal too.

To learn more about these stages of development, read our article on baby growth spurts and developmental milestones.

At What Age Do Sleep Regressions Happen?

The 4-Month Sleep Regression

The 4-month sleep regression is the best known and has the clearest physiological explanation.

Newborns spend approximately half their sleeping time in active sleep, which is similar to REM sleep, compared with around 20% in adults.

Around 3 to 4 months, babies' sleep patterns gradually begin to change. Their sleep cycles become more structured, with alternating periods of light and deep sleep that increasingly resemble adult sleep patterns. However, these changes happen at different rates for different babies.

Brief awakenings between sleep cycles are normal, even in babies who generally sleep well.

During this period, however, some babies wake more frequently between cycles and need additional comfort or support to settle back to sleep.

Common signs include:

• More frequent waking during the night.
• Shorter daytime naps.
• Taking longer to fall asleep.
• Increased fussiness or irritability.

For more information, explore our article on how babies' sleep stages develop from birth to six months.

At this age, many babies are also discovering how to grasp objects and beginning to roll over. They may practise these new movements in their cot, sometimes waking themselves up in the process.

You might also be interested in our article: When do babies start rolling over?

What About the 6-Month Sleep Regression?

Many parents also talk about a “6-month sleep regression”.

Although this is not considered a distinct developmental stage of sleep regression, several changes often happen around this age.

A baby's first teeth usually begin to appear at around 6 months. Babies also become increasingly interested in their surroundings and often start learning to sit up.

All these new experiences can contribute to a few unsettled nights.

The 8, 9, or 10-Month Sleep Regression

Between 8 and 10 months, babies often make exciting progress with their physical development.

They may begin crawling, pulling themselves up against furniture, or even moving sideways while holding onto the sofa.

It's not unusual for a baby to pull themselves into a standing position in their cot during the night, only to realise they don't yet know how to sit back down!

This is also a common age for separation anxiety, which often begins around 8 months.

Your baby is becoming more aware that you can leave the room, and your departure may trigger tears at bedtime or during night waking.

As a result, falling asleep may become more difficult, nighttime awakenings more frequent, and naps shorter.

A helpful tip: During the day, gently show your baby how to lower themselves from standing to sitting. Once they've mastered this skill, they may be less likely to need your help when they find themselves standing in their cot.

The 12-Month Sleep Regression (1 Year)

Around their first birthday, many babies are learning to take their first steps, and their first molars often begin to emerge around this age.

Both developments can contribute to more unsettled nights.

One common mistake is assuming that a baby is ready to drop a nap simply because they suddenly start refusing their morning sleep.

At 12 months, most babies still need two naps during the day. The transition to a single nap usually happens around 18 months.

It's therefore worth continuing to offer both naps, even if one becomes shorter for a few days.

For more guidance, discover our article on baby naps and how much daytime sleep children need.

The 18-Month Sleep Regression

At 18 months, separation anxiety can still be a significant part of a toddler's development.

Children are also becoming more independent, expressing their wishes more strongly (it's often the age of “no!”), and making rapid progress with language.

This is also a common time for the transition to one daytime nap, while additional teeth may still be coming through.

These changes can lead to bedtime resistance, crying when it's time to sleep, or more frequent night waking.

Try to stay calm and consistent. Familiar routines and clear, predictable boundaries are often more reassuring than renegotiating bedtime every evening.

The 2-Year Sleep Regression

By the age of 2, children's imaginations are developing rapidly, and new bedtime fears may begin to appear.

Your toddler might suddenly become afraid of the dark, monsters, or unfamiliar noises.

At the same time, their desire for independence is growing stronger. Some children become experts at delaying bedtime with endless requests for another story, another drink, or one last cuddle.

Big changes in family life can also affect sleep, including moving house, welcoming a new baby brother or sister, or transitioning from a cot to a toddler bed.

For more advice, read our articles on how to help children overcome their fear of the dark and when to move from a cot to a toddler bed.

How Long Does a Baby Sleep Regression Last?

A sleep regression often lasts one to two weeks, but the duration can vary considerably from one child to another.

Some periods of disrupted sleep last longer, particularly when several changes happen at the same time.

For example, your baby might be learning a new skill while also teething, starting nursery, or recovering from a cold.

If your baby's sleep remains disrupted for several weeks, it may be helpful to consider other possible causes, such as:

• Illness or discomfort.
• Teething.
• Hunger.
• A bedroom that is too warm or too cold.

Keeping a baby sleep diary can also help you understand what's happening.

Try noting your baby's bedtime, night waking, and daytime naps for a few days. This may help you identify patterns and recognise when your little one is becoming tired.

Baby Sleep Regression: What Can You Do to Help?

Sleep regressions can be exhausting, especially when you thought the sleepless nights were finally behind you.

The good news is that you don't need to find a perfect solution or completely change your baby's routine. A few simple habits can help make this period more manageable.

• Keep a consistent bedtime routine: A bath, pyjamas, a bedtime story, a cuddle, and then sleep. Repeating familiar steps helps your baby recognise that bedtime is approaching. Discover our article on the best bedtime routines for babies.
• Try putting your baby down when they're drowsy but still awake: This is an option, not a requirement. Some babies gradually learn to fall asleep independently and settle themselves after brief awakenings. Read more in our guide on helping your baby learn to fall asleep independently.
• Observe your baby briefly before stepping in: Some babies make little noises or fuss for a moment before settling back to sleep. If your baby cries or needs you, respond with comfort and reassurance.
• Keep familiar habits without putting too much pressure on yourself: Try to maintain your usual bedtime routine while responding to your baby's needs for comfort or feeding. It's perfectly normal to make temporary adjustments during a particularly difficult period.
• Make sure your baby feeds well during the day: This can help prevent hunger from adding to nighttime awakenings. Remember that some babies still naturally need night feeds.
• Give your baby opportunities to practise new skills during the day: Rolling over, crawling, pulling themselves up, and learning to sit back down are all exciting developmental steps.
• Protect daytime naps: An overtired baby may find it harder to settle at bedtime, so try to maintain appropriate opportunities for daytime sleep.
• Create a calm atmosphere before bedtime: Dim the lights and avoid screens or overly stimulating games in the period leading up to sleep.
• Look after yourself too: If possible, take turns with your partner during the night and accept help from family or friends. You don't have to manage every difficult night on your own.

For more practical advice, read our article: My baby keeps waking up at night: what can I do?

When Should You Speak to Your Paediatrician?

A sleep regression is not an illness in itself. However, it's important not to assume that every change in your baby's sleep is simply part of their development.

Contact your paediatrician if:

• Your baby has a fever or seems unwell.
• They're drinking or eating significantly less than usual.
• They appear to be in pain, cry inconsolably, or repeatedly pull at their ear.
• They snore loudly or seem to have pauses in their breathing during sleep. You can also read our article on snoring in babies and young children.
• Their sleep remains disrupted for several weeks without improvement.
• You feel exhausted, overwhelmed, or unable to cope with the ongoing sleep difficulties.

If you're concerned about your baby's health or behaviour, it's always reasonable to seek medical advice rather than waiting for the supposed sleep regression to pass.

Creating a Comfortable Sleep Environment with Zizzz

During unsettled periods, babies may move around more in their sleep and easily kick off loose covers.

A Zizzz baby sleeping bag provides warmth suited to the room temperature without the need for a loose blanket in the cot.

A properly fitting sleeping bag also allows your baby to move freely, with their arms unrestricted and plenty of room to kick their legs.

To find the right level of warmth for your baby's sleeping environment, take a look at our TOG rating and room temperature guide.

For warmer nights, our organic cotton summer sleeping bags offer a lighter option.

For older children, a cuddly toy made from natural materials can become a familiar and comforting part of their bedtime routine.

However, for babies under 12 months, the cot should remain free from cuddly toys, soft toys, and other soft objects.

Frequently Asked Questions About Baby Sleep Regression

How Long Does the 4-Month Sleep Regression Last?

The 4-month sleep regression often lasts one to two weeks, although this varies from baby to baby.

Around 4 months, babies' sleep patterns gradually become more structured. Some babies need additional time, comfort, and support before their nights become more settled again.

Do All Babies Experience Sleep Regressions?

No. The ages of 4 months, 8 to 10 months, 12 months, and 18 months are commonly mentioned by parents, but research has not found that all babies experience a predictable decline in sleep at these specific ages.

Some babies pass through these developmental stages without any noticeable disruption to their sleep.

Sleep Regression or Teething: How Can You Tell the Difference?

Tender gums, increased drooling, and a stronger urge to chew on objects can all be signs of teething.

The first teeth generally begin to appear around 6 months, while the first molars often emerge around 12 months.

However, night waking can have several causes, and more than one may occur at the same time.

If you're unsure what's causing your baby's discomfort, particularly if they seem to be in pain, ask your paediatrician for advice.

Should My Baby Drop to One Nap During the 12-Month Sleep Regression?

Generally, no.

At 12 months, most babies still need two daytime naps, and the transition to a single nap usually happens closer to 18 months.

Temporarily refusing a morning nap doesn't necessarily mean your baby is ready to stop having it altogether.

Is a Sleep Regression a Sign That Something Is Wrong?

Not usually. Changes in sleep often occur alongside normal developmental milestones.

However, contact your paediatrician if your baby has a fever, is feeding less than usual, seems to be in pain, or continues to experience disrupted sleep for several weeks without improvement.

Sources

• Cleveland Clinic – The 4-Month Sleep Regression: common signs, duration, and practical advice.
• Sleep Foundation – Baby Sleep Cycles: the proportion of REM sleep and how sleep cycles develop around 3 to 4 months.
• ParentData – Are Sleep Regressions Real?: what research shows about changes in babies' sleep patterns over time.
• MSD Manual – Separation Anxiety and Stranger Anxiety: when separation anxiety typically begins and how it develops.
• Santé.fr – La sieste, sommeil de l'enfant en journée: recommended daytime naps at different ages (in French).
• NHS – Baby Teething Symptoms: when the first teeth and molars typically appear and common signs of teething.
• NHS – Helping Your Baby to Sleep: how babies' sleep and feeding needs vary from one child to another.
• NICHD – Safe to Sleep (French-language brochure): safe sleep recommendations, including keeping soft toys and other soft objects out of a baby's cot.

This article is for informational purposes only and is not a substitute for professional medical advice.