Baby Care

It’s Impact on Baby Sleep– Nested Bean


You might have seen the Wonder Weeks chart before, and you may even be tracking them with your own baby, but do you know how they can impact your little one’s sleep?

There are many different measures of a baby’s growth, from weight and height to cognitive abilities, and one way of keeping track of your little one’s changes is through something called The Wonder Weeks. These weeks are vital for your baby to bloom into childhood and beyond, but they can sometimes impact other areas of their life – specifically, their sleep cycles.

Here, we’ll talk you through what Wonder Weeks are, their importance, and how each Wonder Week can effect your baby’s sleep – as well as ways to help them have better sleep no matter the week.

Wake Windows Infographic of babies

What are The Wonder Weeks?

Your baby goes through some unbelievable changes in their first year of life, and we as parents love tracking these developmental milestones, from lifting their head alone to their first words and steps. But these are the more visible changes – what about the major changes we don’t see?

This is where Wonder Weeks come into play.

Established by by physical anthropologist Hetty van de Rijt and developmental psychologist Frans Plooij in the Netherlands in the early 1990s, the Wonder Weeks chart refers to eight ‘leaps’ that your baby goes through in their first year of life. These weeks each refer to the development of a new skill or sensation – and understandably, this can be an exciting yet stressful time for babies!

Here’s how mom Emilee Janitz explains the leaps in an honest review of the book for The Everymom:

According to The Wonder Weeks—a bestselling book and popular mobile app—babies’ cognitive development follows a predictable timeline. During the first 20 months of their life, each baby will experience 10 separate leaps. After each leap, the baby will demonstrate new skills as their mental development progresses.

While the prospect of watching your baby learn new skills is really exciting (from learning to babble in leap four to understanding the flow of events and relationships in leap seven), the temporary side effect that leaps have on a baby’s disposition is less so.

In other words, if your near-angelic infant is suddenly a wild beast set on avoiding sleep and keeping you glued to their side, they’re probably in the throes of a leap. 

How each wonder week can impact sleep of Babies

As each Wonder Week involves the development of a different element of your baby’s brain or body, each one also has a different effect on your baby’s sleep. For instance, while some weeks will have little impact, others may introduce new skills that your little one wants to try at night, or may even lead to issues like nightmares or separation anxiety.

You may also find that your baby becomes more fussy at the very start of a leap – in fact, though frustrating for parents, this is a great sign that your baby is developing properly! In the Wonder Weeks book (and on the Wonder Weeks app), this is referred to as the ‘three Cs’: Crying, Clinginess, and Crankiness.

That’s why it’s important to understand what goes on during each Wonder Week and how it’s likely to effect your baby. It’s important to remember that these weeks are calculated from your baby’s due date rather than their birth, so bear that in mind as you read ahead if your baby was born early or late.

4 weeks

The first leap week is all about sensations – not only will your baby now be able to produce tears, but they’ll also be able to see better beyond a 12 inch distance. These sensory developments, along with developments around their metabolism and digestion, lead them to react much more to the people and events around them than they previously have in their sleepy newborn state.

As you can imagine, this greater awareness of the world around them can sometimes lead to more fussiness when they’re trying to sleep, as they’re suddenly noticing much more of what goes on around them.

This can be combatted by keeping the room they snooze in calm and quiet so they don’t become overstimulated – try using blackout blinds and a white noise machine and keeping the room relatively empty, for example.

8 weeks

Wonder Weeks for babies at 8 weeks

This leap marks when your baby is able to recognise patterns more clearly – the world isn’t such a random chaotic place, and they’re able to consciously make movements as they become more aware of themselves and how their body fits together.

Understandably, this new awareness – coupled with physical development that allows for greater movement – means that they might want to practice new skills rather than fall asleep. This is where a consistent sleep routine can come into play – if they can recognise that their bath and bedtime story means it’s time to snooze, they might find it easier to catch some Zs.

11 weeks

The third leap is when your baby experiences ‘smooth movements’ for the first time, in contrast to the more jerky, wooden motions they made from reflexive instincts rather than conscious decisions.

This is why babies love to be bounced and lifted into the air by parents, and is also why you’ll start to see them bring more objects to their mouth and make more independent head movements.

Along with the classic three Cs, your baby may be quieter or less energetic than usual during this leap, which is perfectly normal. In fact, this calmer state may even mean that they sleep more easily, so enjoy this while it lasts!

14 weeks

Wonder Weeks for babies at 14 weeks

This leap is all about events – now, instead of just individual movements, they can put together actions into a sequence, put sounds together to start babbling, and even take part in simple games with toys!

While this is the time when you’ll start to see even more of your little one’s unique personality, many parents find that it’s also one of the fussiest leaps – and that sleep can be hard to come by. This is also a transitional time in another way, as 14 weeks is around the time when babies start to show signs of rolling, and therefore of outgrowing their swaddle, which can potentially make sleep even trickier.

If you want to keep your baby comfortable with and without swaddling, why not try our adaptable Zen One? This unique piece of sleepwear can transform from a swaddle to a sleep sack just by taking off the removable sleeves, and the carefully placed Cuddle Pads mimic your touch to help your baby soothe themselves to sleep.

22 weeks

At roughly 22 weeks, your baby will start to go through the fifth leap week, which enters them into ‘the world of relationships’. In addition to understanding events, your baby will now have a better understanding of the relationships between people or objects – they might now grasp when a block is behind a teddy bear, or when you’re leaving the room, for instance.

Because this leap is about your baby’s sense of object permanence – the ability to understand that objects and people still exist even when you can’t sense them – it can also spell the beginning of separation anxiety.

That’s why this is also a great time to sleep train your baby with a sleep training method of your choice; if they can snooze independently and feel secure without you, you can help reduce their anxiety and have a happy baby even at bedtime.

33 weeks

Wonder Weeks for babies at 33 weeks

The sixth leap centers around categorization – their ability to group things together according to common traits. This is closely related to how they engage with the big world around them, and involves skills like being able to understand that bananas and apples are both fruits, or that cows and pigs can both be found on a farm.

This is a great time to stimulate your baby’s mental skills with toys and games – this is a skill they’ll want to practice, and it can be a great opportunity for some bonding time too! Keeping them occupied mentally may also help if they’re too lively to sleep at night, so make sure to get their energy out by engaging with their new abilities.

41 weeks

The ‘world of sequences’ that your baby discovers in their seventh leap is one of the most exciting, as its when they’ll start to put many of their new skills into action. For instance, while they were previously aware of individual actions, they may now be able to put them into an order and try things out for themselves.

This can be a messy time – particularly if eating or baby arts and crafts are involved – but it’s vital to keep your baby stimulated and to practice these abilities.

Again, you may find that your little one is feeling fussy at the start of this leap, but at 41 weeks, they’ll be too big for a swaddle – and they need their rest for all these growth spurts! Instead, you can try our Zen Sack wearable blanket, gently weighted to mimic your soothing touch and to help your little one snooze independently through short naps or long stretches of night sleep.

This is what Zen Mom Martha E. has to say about her son’s five star experience with the Zen Sack:

I’m not sure what kind of magic is in this sleep sack but it’s amazing! My son immediately calms down and falls right asleep every time he is put in it. I recommend these to all of my friends with babies now!

50 weeks

Wonder Weeks Chart for babies after 50 weeks

Congratulations – your baby is almost a year old, and is about to enter the final leap week before their first birthday! This week is about programs – putting everything they’ve learned all together as one cohesive whole.

For instance, while they might have understood putting clothes in the washer, hanging them out to dry, and folding them and putting them away individually before, they’ll now be able to perceive actions like this as part of one thing: doing the laundry! Letting them engage with you in activities like these can made a big impact on their development and understanding of the world, so make chores part of playtime where you can.

Unfortunately, this last leap can come with some new challenges around sleep – specifically, this is the period when your little one might start experiencing some nightmares. If this happens, you can use aids such as a nightlight or a teddy bear to keep them company, and try to help them understand that their room is a safe space for sleep – especially as a lack of sleep can actually lead to more nightmares from stress.

So whichever leap week you’re finding yourself in, just remember that the fussiness is only temporary – but these new skills will last them a lifetime!

Commonly asked questions about baby wonder weeks and sleep

What are wonder weeks?

Wonder Weeks, also referred to as leap weeks, are weeks in which your little one experiences a sudden new development in their skills and understanding of the world around them. They were first detailed in a wonder weeks book released in 1992, and are now popular worldwide as a way of measuring your baby’s growth.

There are ten leaps in total, and eight of these are experienced before your baby reaches their first birthday. However, in addition to bringing new skills, they can also have an effect on your baby’s mood, leading to fussiness that can negatively impact their sleep. To counteract this, you can use tools like sleep training, a regular schedule, and a soothing bedtime routine with our gently weighted Zen Sleepwear.

How do wonder weeks effect baby night sleep?

Because each leap is marked by your baby experiencing the three Cs – Crying, Clinginess, and Crankiness – fussiness can have an impact on their sleep, from causing nighttime wakeups that they struggle to self-soothe back to sleep from, to preventing them from falling asleep to begin with.

Luckily, this is only temporary, and actually serves as a positive sign – your baby is reaching a new milestone! But it can still be frustrating, which is where sleep aids like our Zen Sack can come in handy. Gently weighted with strategically placed Cuddle Pads to mimic your soothing touch, this wearable blanket can soothe babies too big for swaddling and help them self soothe even during leaps.

Are babies fussy during leap weeks?

The start of a leap week tends to be signalled by fussiness, and by the ‘three Cs’ in particular – these are Crying, Clinginess, and Crankiness. So if you’ve found that your baby is being a little fussier than usual, congratulations – they’re likely to be hitting a major developmental milestone soon!

You may also like

Your baby’s wake windows by age

Celebrating the maternal ‘instinct’ – in everyone

Fussy baby: causes and how to soothe


Athena S.



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