What are The Wonder Weeks, and how do they affect sleep? (Part One)

‘The Wonder Weeks’ is a book that was written by a husband and wife who completed their studies in Educational Psychology, Physical Anthropology and Behavioural Biology. After spending two years studying the behaviours of chimpanzees in Tanzania, East Africa, they returned to Europe and compiled their data. Analysis determined that there were significant ‘regression’ periods where the infant would cling more to the mother, and this was found to be the case in at least 12 other primate species.

After completing their Ph.D. degrees, the couple went on to observe human mothers and infants and found that they too experienced similar ‘regression’ periods and similar behaviours as a result. At the same time, these infants would make a ‘leap’ in their mental development.

What are The Wonder Weeks?

The Wonder Weeks consist of ten developmental growth spurts (or these ‘regression’ periods, as mentioned above) that a child experiences in their first 82 weeks of life. Although they often coincide with physical growth spurts, they are actually a different phenomenon and are usually marked by a child becoming increasingly clingy, cranky, and crying more often.

Each Wonder Week (or ‘Leap’, as it’s sometimes referred to) can last anywhere from 3 days to [gulp]… 6 weeks! But the good news is that the most intense behaviours usually don’t last for more than 1 to 2 weeks, with some Wonder Weeks not affecting a child at all. I also find that each Wonder Week is fairly accurate based on a child’s due date (not date of birth), give or take a week.

But the big question you’re all wanting me to answer here is…

How do they affect sleep?

Wonder Week 5 – Changing Sensations

This Leap begins around 4.5 weeks and ends around 5.5 weeks.

A child this age is ‘waking up’ to their world. It’s often a tough Leap, as it tends to coincide with three other significant changes:

1. The beginnings of the ‘Witching Hour’ – that time of night when this age group likes to cluster feed, ranging anywhere from 4pm to 10pm. Luckily most children have a ‘Witching Hour’ that is usually no more than a few hours at a time. What’s interesting though is that their ‘Witching Hour’ can often stay with them until they are 5 years or even older – they simply learn to express their needs in different ways.

2. A physical growth spurt around 6 weeks.

3. The normal 6 week peak in fussiness, particularly if the child has been diagnosed with colic.

Needless to say, sleep at this time often becomes quite the struggle!

The sleep issue during this Leap is often overstimulation from their day, resulting in overtiredness. A child this age needs to be asleep every 45 to 60 minutes, and this can be difficult especially at the end of the day when dinner needs to be cooked and the family is arriving home.


Wonder Week 8 – Patterns

This Leap begins around 7.5 weeks and ends around 9.5 weeks.

A child this age is becoming increasingly alert and aware of their environment.

The sleep issue during this Leap is often overstimulation from their environment. The sleep environment needs to be ‘womb-like’, making it perfectly conducive to sleep. When creating ‘womb-like’, think dark, at a comfortable temperature, and with white noise.


Wonder Week 12 – Smooth Transitions

This Leap begins around 11.5 weeks and ends around 12.5 weeks.

A child this age is becoming increasingly active, with smoother and stronger movements.

The sleep issue during this Leap is often breaking free from the swaddle, due to the new-found movements. Parents often think that this means the child no longer ‘wants’ to be swaddled, however some children still have their moro reflex at this age and therefore still need to be swaddled. If this is the case, it’s important to either find a more age-appropriate swaddling method, or to invest in a swaddling product.


Wonder Week 19 – Events

This Leap begins around 14.5 weeks and ends around 19.5 weeks.

A child this age is learning cause and effect (ie. If I throw my toy on the floor, mum will pick it up!). This too is often a tough Leap, as it tends to coincide with the 4 month sleep regression – the time in a child’s life where the way they sleep fundamentally changes, along with another physical growth spurt.

The sleep issue during this Leap is often a lack of routines. Children don’t usually like surprises, and especially when learning cause and effect – they want to know that when ‘this’ happens, ‘that’ happens as a result. They don’t like the surprise of bedtime when they didn’t expect it, and instead like a routine which shows them that ‘bath’ followed by ‘milk’ followed by ‘lullaby’ results in ‘bedtime’, as an example.


Wonder Week 26 – Relationships

This Leap begins around 22.5 weeks and ends around 26.5 weeks.

A child this age is learning about the distance between objects and people, which is what encourages them to get moving through rolling and crawling. This too is often a tough Leap, as it tends to coincide with them learning about object permanence – the understanding that objects continue to exist even when they cannot be observed, and another physical growth spurt.

The sleep issue during this Leap is often separation anxiety and new-found mobility.

With separation anxiety, helping a child to learn that you aren’t gone for good is a great way to help them through this Leap. Playing games like peek-a-boo (from both behind an object, and from an adjoining room) will help a child to learn that just because you aren’t in sight, doesn’t mean that you are completely gone. And just because you go, doesn’t mean that you won’t come back.

With new-found mobility, help your child to practice their new skill while awake, in and out of bed, so that they can master their new skill quickly and no longer feel the need to practice it when they should be asleep.


As with all stages in a child’s life, The Wonder Weeks are temporary. If you’re experiencing a tough one, just remember that ‘this too shall pass’! The good news is that a child who has learnt the skills required to sleep well is much less affected by The Wonder Weeks, so if you feel that you need some help, feel free to contact me because I would love to help you!

I’d love to hear your thoughts on the topic!