What Are Wonder Weeks?

Growth spurts.

Appetite increases.

Fussy periods.

All new mothers know there are times when babies are extra unsettled due to development. When mothers come together to talk, they find their babies go through these stages at similar ages. “It’s just a phase” is commonly said to reassure them, by experienced mothers, doctors and nurses.

Modern mothers have come to know these stages by another name: Wonder Weeks.

Wonder Weeks is a popular book written after 35 years of research and observation by Dutch paediatricians Hetty van de Ritj and Frans Plooij. They spoke to parents and found these difficult periods are usually accompanied by the three C’s: clinginess, crankiness, and crying. And these stages were not related to physical growth as suggested by the term “growth spurt” and can’t be measured by scales and charts. What babies are actually overwhelmed by is much more complex: these fussy periods were the result of brain development.

While we all proudly mark off the age our babies reach milestones in their baby books (or at least, intend to!), the period before they are achieved is actually a time of significant growth and development within the brain and central nervous system. Not surprisingly, such rapid development is demanding and babies usually breastfeed more, sleep less and generally increase their need for parental support around the clock.

By understanding how this development progresses, when to expect change and how to support babies through it, parents feel better prepared and are less likely to worry that something is wrong with their baby or how they are parenting. When those around them also understand these stages, they can support and encourage parents.

So – when are these Wonder Weeks and what happens when they occur?

Each developmental “leap” is preceded by a period of fussy behaviour – often several weeks long. The Wonder Weeks book and the popular app which goes with it, identify these stages based on the gestational age of the baby, regardless of being born early, late or right on their due date. Parents calculate the calendar as beginning 40 weeks after conception. The arrival of Wonder Weeks is so predictable that, even though individual babies may experience them a week or two either side of the date, parents can reliably expect their arrival on time!

·         Leap One – Wonder Week Five – occurs four or five weeks after baby’s due date and is known as The World of Changing Sensations.

·         Leap Two – Wonder Week Eight – can be expected at eight weeks and is The World of Patterns

·         Leap Three – Wonder Week 12 – hits as the baby turns three months old. The World of Smooth Transitions

·         Leap Four – Wonder Week 19 – is just one of the big developmental stages to occur around four months. The World of Events

·         Leap Five – Wonder Week 26 – around six months is The World of Relationships

·         Leap Six – Wonder Week 37 – as the baby turns nine months The World of Categories

·         Leap Seven – Wonder Week 46 – around 10 ½ months introduces The World of Sequences.

·         Leap Eight – Wonder Week 55 – occurs just after baby’s first birthday and is The World of Programs

·         Leap Nine – Wonder Week 64 – hits as baby approaches 15 months and is The World of Principles

·         Leap Ten – Wonder Week 75 – is the final recorded leap as the baby is 17 months old The World of Systems

How each Leap affects babies behaviour and abilities is detailed in the book and summarised in the app. The consistent pattern between them is the period of crying, crankiness and clinging which lasts anywhere from days to weeks before the Leap. Some Leaps are more complex than others or occur alongside physical development such as teething, rolling, crawling and walking – making them more demanding for baby and parents. Leaps Four, Six and Nine are particularly difficult.

Every baby is different and each will face these developmental process in their own way. Some are especially sensitive to change and will need extra comforting while others take it in their stride and move on. Parents also vary in how they manage during these stages. Anxiety about other causes of the baby’s distress or fear the behaviour is due to feeding or sleep issues can make it more challenging for them. Reassurance that all babies go through these changes and they are not caused by anything parents do – or do not do – will help.

The massive development of the human brain in infancy occurs behind the scenes and cannot be measured by weight, height or progression through clothing sizes. However, the concept of Wonder Weeks and the science behind them has given us a way to understand and respect these “growing pains”. Parents can begin to imagine how it must be for a baby to experience the world around him in an ever-evolving body and celebrate the wonder of it all.