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Wonder Weeks Chart: What are Wonder Weeks/Baby Leaps?

Impact on Baby Sleep


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?

Or, maybe you’re looking to start from the beginning: what are wonder weeks? 

There are many different measures of a baby's growth, from weight and height to cognitive abilities. But, one way of keeping track of your little one's changes is through something called The Wonder Weeks

Also known as baby leaps, 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 baby leaps are, their importance, and how each Wonder Week can affect 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 Wonder Weeks?

First things first…what are 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, also known as baby leaps, come into play.

Established 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 chart and the bestselling book and popular mobile app that accompanies it, 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 affect 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.

The Wonder Weeks Calendar

Below, we’ll walk you through the various baby leaps so you know what to expect at each stage. First is the 4 week milestone:

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.

You can also use soft, calming music during bedtime to create a soothing atmosphere. Warm baths can help relax your baby before sleep.

8 weeks

Wonder Weeks for babies at 8 weeks

This leap marks when your baby is able to recognize 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 newborn bedtime routine can come into play - if they can recognize 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 newborn reflexes rather than conscious decisions. Your baby may begin to lose their Moro reflex at this point.

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 baby 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 it's 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. 

What are the sleep sack benefits, you ask? How about we let Zen Mom Martha E. tell you 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!

If your baby is resisting bedtime, consider slightly adjusting their daytime naps or incorporating more physical play during the day to ensure they are tired by bedtime.

This is an excellent time to establish a bedtime ritual that includes hygiene like brushing gums or teeth, as they are likely getting into routines and sequences.

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 together as one cohesive whole.

For instance, they might have understood how to put clothes in the washer, hang them out to dry, fold them, and put them away individually before. But now, they'll 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 make 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!

How do wonder weeks affect baby's 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 to preventing them from falling asleep and staying on a newborn sleep schedule 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 be perfect for a self soothing baby who is too big for swaddling, as it helps them self-soothe even during baby leaps.

Learn more about the difference between a sleep sack vs swaddle in our blog. Then, choose among the different types of swaddles here at Nested Bean. 

Whether you go with our bamboo swaddle, zipper swaddle, or arms up swaddle - which we consider to be the best transitional swaddle - you can rest assured you’re getting quality weighted sleepwear that will help you keep your child asleep. Or, learn more about our weighted sleep sack, bamboo sleep sack or winter sleep sack

Along with the best sleepwear for babies, we have tips on how to get newborn to sleep at night, including the best swaddling techniques (and how to swaddle a baby in general), sleep training baby, baby massage for sleep, what age to stop swaddling, what to do if your newborn won't sleep unless held, and the signs of sleep regression

Are babies fussy during leap weeks?

The start of a leap week tends to be signaled 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

Wrapping Up Our Breakdown of the Wonder Weeks Chart

Navigating the first year of your baby's life is like a roller coaster of emotions, filled with exhilarating highs and some inevitable lows. 

From the first coo to the first step, each developmental leap - often charted as baby leaps or wonder Weeks - offers both challenges and opportunities. The fussy phases are but fleeting moments, yet the skills your baby gains are for a lifetime.

Now that you have a road map for what to expect during each of these significant periods, you're well-equipped to guide your little one through these crucial developmental milestones. Remember, as you weather each leap's unique sleep disruptions and behavioral changes, this too shall pass.

For those especially challenging weeks, when neither you nor your baby seem to be getting enough rest, consider turning to our Zen Sack from Nested Bean. 

Designed with your baby's comfort in mind, the Zen Sack mimics your reassuring touch, helping your baby self-soothe even during the fussiest leaps. 

It's like an extra set of hands when you need it most, allowing you some well-deserved respite while ensuring your baby sleeps more soundly.

Learn more about parenthood in our blog with tips on how to hold a newborn, using a sleep aid for infants, how to help dad bond with baby, when do toddlers stop napping, and more.

Happy parenting, and here's to cherishing each and every one of your baby's wonder-filled weeks! 🌟

Athena S.

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