They’re periods when your baby is particularly fussy. You may even notice behavioural changes. Welcome to the Wonder Weeks. Here’s how to survive them.
Often referred to as “fussy weeks”, “stormy weeks” or “baby leaps”, Wonder Weeks are the times when your baby is going through big developmental leaps. With this can come difficult behaviour: Increased fussiness, sleep disturbances, regressions.
While every baby is different, research shows that most babies hit these eight milestones at similar times, between week five and around 20 months. Unlike physical growth spurts that focus on size and weight, Wonder Weeks are all about mental development. These leaps shift how your baby sees and understands the world, which can cause temporary changes in their patterns.
While these leaps bring exciting new skills, it can be very helpful for parents to have some expectations as to when they occur to help prepare.
What are the baby leaps?
The idea of Wonder Weeks was first explored in the early ’90s by Dutch researchers Hetty van de Rijt and Frans X Plooij. They discovered that babies undergo predictable mental development changes, and their work was later expanded by Xaviera Plas-Plooij. This research eventually led to the creation of the Wonder Weeks app and book, which many parents use to better understand and navigate their child’s growth.
In the first year of your baby’s life, they will go through no fewer than eight leaps. These leaps are when your baby’s brain has a developmental change. During this time, your baby’s perception of the world around them will suddenly become very unfamiliar. These changes are categorised as mental leaps due to the big cognitive shifts going on in their brains.
As your baby’s world is rapidly changing during leaps, they may experience more separation anxiety or a sudden sleep regression.
During these phases, your little one may need extra attention and closeness. You might find that simple tasks like putting them down or stepping away become much harder. A baby’s mental development comes in major milestones and takes a lot of energy from them, so it’s important to prioritise connection and restfulness (for both of you).
Not every leap feels the same, though, and some babies handle certain leaps better than others. It’s all part of their growth, but it can definitely test your patience.
The two phases of a Wonder Week
Experts believe that each Wonder Week consists of two phases:
1. The fussy phase:
Babies become more clingy, irritable and demanding as their brains adjust to new perceptions.
2. The skill phase:
Babies begin using their new skills, often surprising parents with what they suddenly understand and can do. As a baby’s brain matures, they gain the ability to recognise patterns, respond to social cues and interact with the world in more complex ways.
Recognising the Wonder Weeks
While every baby follows their own developmental path, the eight leaps of Wonder Weeks generally occur around the following ages:
Week 4
The first developmental leap is centred around sensory awareness. At this stage, your baby begins to perceive the world more vividly—they can now shed real tears and see beyond 30 centimetres. Alongside these sensory advancements, their metabolism and digestion are also maturing, making them more responsive to their surroundings, compared to their earlier sleepy newborn phase.
This heightened awareness can sometimes lead to increased fussiness, especially during sleep, as they become more sensitive to sights and sounds around them. To help your baby settle, create a calm and quiet sleep environment. Consider using blackout curtains to reduce visual distractions, a white noise machine to mask background sounds and keep the sleep space clutter-free.
Additionally, incorporating soothing bedtime routines—such as playing soft lullabies or giving your baby a warm bath—can help them relax and transition more smoothly into sleep.
Week 8
During this developmental leap, your baby begins to recognise patterns more clearly, making the world feel less random and chaotic. They are also becoming more aware of their own body and how their movements connect, allowing them to start controlling their actions with more intention.
With this new-found awareness and increased mobility, your little one may be more interested in practising their new skills rather than abiding by their usual sleeping patterns. This is where a consistent bedtime routine can be especially helpful. Establishing familiar cues—such as a warm bath followed by a bedtime story—can signal to your baby that it’s time to wind down, making it easier for them to drift off to sleep.
Week 11
During the third developmental leap, your baby begins to develop smoother, more controlled movements, moving beyond the jerky, reflexive motions of the newborn stage. This is also when the Moro reflex (newborn startling reflex) starts to fade, allowing for more intentional coordination.
At this stage, babies often enjoy being gently bounced or lifted into the air, as their growing sense of movement brings them joy. You’ll also notice them bringing objects to their mouth more frequently and gaining better control over their head movements.
Alongside the usual signs of fussiness—crying, clinginess and crankiness—your baby may also seem quieter or less active than usual. This is completely normal and can even lead to longer or easier sleep. If that’s the case, take the opportunity to enjoy some well-deserved rest while it lasts!
Week 14
This developmental leap is all about sequences—your baby is now learning to combine movements, string sounds together to start babbling and even engage in simple play with toys.
As their personality shines through more than ever, many parents also find this to be one of the fussier leaps, often disrupting sleep. Around 14 weeks, babies may also begin showing signs of rolling, which means they’re likely starting to outgrow their swaddle. This transition can make settling down for sleep even more challenging.
To help your little one adjust, consider using a flexible sleep solution that provides comfort both with and without swaddling. Sleepwear that transitions from a swaddle to a sleep sack can make the change smoother and gentle pressure features—like weighted pads or snug fabrics—can offer a soothing sensation similar to your touch, helping your baby feel secure as they drift off to sleep.
Week 22
Around 22 weeks, your baby enters the fifth developmental leap, often called the “world of relationships”. At this stage, they begin to understand how people and objects relate to each other. For example, they may start recognising that a toy is hidden behind another object or become more aware when you leave the room.
This leap is closely tied to the concept of object permanence—the understanding that things and people continue to exist even when out of sight. While this is an exciting cognitive milestone, it can also bring the first signs of separation anxiety, making your baby more clingy and unsettled when you’re not nearby.
Week 33
The sixth developmental leap focuses on categorisation—your baby’s ability to group objects based on shared characteristics. This skill helps them make sense of the world around them, such as recognising that apples and bananas are both fruits or that cows and pigs belong on a farm.
This is a wonderful time to encourage their growing mental skills through interactive play. Providing toys and activities that involve sorting, matching or grouping can help them practise this new ability while also creating opportunities for quality bonding time.
Keeping their mind engaged during the day may also help with night-time restlessness. If your baby seems too energetic at bedtime, offering stimulating play during the day can help them burn off some of that excitement, making it easier for them to settle down for sleep.
Week 41
During the seventh developmental leap, often called the “world of sequences”, your baby begins to put their growing skills into action. While they may have previously recognised individual actions, they can now start organising them into steps—trying things out in a more intentional way.
This phase can get a little messy, especially when it comes to eating or creative play, but encouraging these new abilities is essential for their learning and development. Hands-on activities like stacking blocks, playing with textured materials or even exploring finger foods can help strengthen their understanding of sequences.
As with previous leaps, this stage can bring fussiness, making sleep more challenging. By 41 weeks, your baby has likely outgrown swaddling and needs restful sleep to support their ongoing growth and development. To help them settle more easily, consider using a wearable blanket or sleep sack that provides comfort and security while allowing for movement.
If bedtime resistance becomes an issue, slight adjustments to daytime naps or adding more physical play can help ensure they’re ready to rest at night. If you haven’t already, introduce consistent bedtime routines, such as brushing their gums or teeth, which align with their new-found ability to recognise sequences and establish habits.
Week 50
You’re nearing a major milestone: Your baby is almost a year old! As they approach their first birthday, they’ll go through their final developmental leap of the first year. This stage is all about bringing everything they’ve learned together into a more complete understanding of how things work.
For example, while they may have previously grasped individual steps—like placing clothes in a basket, putting them in the washer and folding them—they can now recognise these actions as part of a larger process, like “doing the laundry”. Encouraging their curiosity by involving them in simple household activities can boost their understanding of the world and reinforce their sense of independence.
However, with this exciting progress can come new sleep challenges. Around this time, some babies start experiencing nightmares, which may lead to disrupted sleep or bedtime resistance. A comforting bedtime routine, a nightlight or a familiar stuffed animal can provide reassurance and help them feel secure in their sleep environment. Since stress and exhaustion can contribute to restless nights, maintaining a calm and predictable night-time routine can make a big difference.
Sunny Weeks: The calm after the storm
After a Wonder Week, babies move into what’s known as a “Sunny Week”. During this time, they often seem happier, more content and excited to try out their new skills. You might notice improvements in their sleep and feeding patterns, and they may become a bit more independent. It’s also when your baby might start exploring a little more on their own, get more social and happily play by themselves.
Sunny Weeks can feel like a breath of fresh air for both babies and parents. With your little one feeling more settled, it’s easier to manage your daily routines. These phases offer a nice, much-needed break after the intensity of a Wonder Week, giving everyone a chance to recharge.
Supporting your baby through the Wonder Weeks
Navigating Wonder Weeks can be exhausting, but understanding them can make the experience less stressful. Here are some practical ways to support your baby during these developmental leaps:
Stay flexible
If you notice your baby entering a Wonder Week, adjust your expectations. You may need to change plans or put off tasks to provide extra comfort and attention.
Practise self-care
Parental wellbeing is just as important as the baby’s. Rest when possible, eat well and take short breaks when help is available. It’s a great time to take a little break for some self-care while your baby is napping.
Accept support
If family and friends offer help, accept it. A little assistance can go a long way in managing these challenging weeks.
Celebrate small wins
Recognise that getting through a tough day is an achievement. Find simple ways to reward yourself, whether it’s a quiet cup of tea or a short walk outside.
Offer comfort and reassurance
Babies need extra cuddles and reassurance during Wonder Weeks. Holding, rocking and engaging with them can help ease their distress.
Adapt routines as needed
Your baby’s sleep or feeding schedule may change during the wonder weeks and that’s OK. Being flexible with routines can reduce stress for both parents and babies.
Avoid comparisons
A baby’s development comes at their body and brain’s pace. Comparing your baby’s progress to others can create unnecessary stress. Trust that your child’s development is growing in their own time.
Embracing the ups and downs of the Wonder Weeks
While Wonder Weeks can be challenging, they are also a sign that your baby is growing and developing new skills. No matter which developmental leap you and your little one are navigating, remember that the fussy phases are temporary, but the skills they’re gaining will support them for years to come!
By staying patient, offering comfort and adjusting routines as needed, you can help your baby navigate these changes with confidence. Remember, this phase is temporary and soon, you’ll see the incredible progress they’ve made.
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