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Wonder weeks

fussy; fussing; regression; weeks; unsettled; crying; development; infant; baby; behaviour; wonder; cling; sunny; growth; spurts;

Recent research has shown that there are predictable times during the first few years of a child's life when the child may be more demanding (fussier) than usual. These fussy times have been called the 'Wonder weeks' by some writers, because it is during these more difficult weeks that babies are making big steps forward in their development.



Once they have taken one of these big steps in their development, they may have times when they are less demanding. These times have been called  'sunny' times. These cycles of changes in how much distress a baby experiences have been found to happen in many different cultures.

Before deciding that the reason a baby is fussy due to a 'wonder week', it is important to consider whether the child may be unwell. If a child has a fever, nappy rash or an ear infection for example, the baby will be more distressed than usual.

What is happening during these 'Wonder' weeks?

We know that development in physical skills happens in 'steps' - one day a baby can take a step and start to walk, whereas the day before he could not take that step. Similarly, it is thought that the way that a baby can think, feel, notice and understand what is happening around him (mental development) might also happen in steps.

  • For example, at around the age of 8 weeks, a baby can begin to recognise more of the people and things that she can see around her.
  • At about 6 months she can start to realise that some people are around most of the time (her parents for example), while some people are strangers. Before that time she did not know that some people were strangers.
  • Changes in thinking can show up in changes in what a baby can do, and how she behaves.

During these times when a baby's ability to understand the world around him is changing, he may need more attention.

  • He may cry more, be more fussy and need more comforting. This may be due to other reasons, such as being unwell.
  • Some of the babies lose their appetites.
  • Some babies who have been sleeping well may take more time to go off to sleep and wake more often.
  • Some young children who have been happily exploring their world may become more clingy, and become upset much more easily.
  • They may show an increased need for body contact with their mothers.

Sometimes these weeks are called 'regression weeks', because a baby or young child will seem to have gone backwards in her development. In fact, she is making a big step forward, but this step is confusing to her, and she will behave more like a younger baby.

The 'sunny' weeks

When the baby has fully 'climbed' this developmental step, there may be several weeks when she is happier. She can happily try out her new skills. She may be less easily upset (less temperamental). She may allow you to be out of sight more often, and go off to sleep more easily.


  • Some babies are generally easier to get on with than other babies. They tend to be happier, cry less and go to sleep more easily.
  • Other babies are easily upset and cry a great deal more often.
  • Even 'easy' babies have these fussy 'wonder' weeks. It may be easier to help them calm down when they cry than it is to calm a 'difficult' baby, but there will be times when they are more distressed than usual.

Other things that can cause a baby to be fussy

Babies can be fussy for many other reasons.

  • A baby who is unwell or in pain is likely to be more distressed than usual. A nappy rash, for example, is very painful, and will cause a baby to cry more and have more difficulty going to sleep and have restless sleep.
  • It is often thought that babies are unsettled when they are teething. Research has shown that babies are not more distressed when they re teething, but not everyone is convinced. Maybe the teething has coincided with a fussy developmental stage.
  • An older baby who is separated from his parent may be very distressed when she returns. This is likely to be due to separation anxiety, not 'just a phase'.
  • Some babies have developmental delays or major health problems, which could alter the times that they go through these mental developmental milestones.

How to help your baby during these 'wonder' weeks

  • During these fussy weeks, babies seem to manage the developmental changes more easily if they get extra attention, get held more often and have extra comforting when they go to sleep.
  • Parents need to know that there will be these more difficult times, but that there will also be times when their baby will be happier and more easy to get along with.
  • If parents are not able to give their baby as much attention as he needs, the baby may find this mental developmental step more difficult to manage.


Predicting the 'wonder' weeks

Since most babies follow a similar pattern, it is possible to predict approximately when a child may have a fussy ('stormy') time. Some babies may become more distressed a week or so before or after the times listed here. Some babies may become quite distressed some times, but pass easily through the predicted 'stormy' time at other stages (they may also become very distressed for quite different reasons).

In the first year of life, the stormy times seem to happen around

  • 5 weeks
  • 8 weeks
  • 12 weeks
  • 17 weeks
  • 26 weeks (6 months)
  • 36 weeks
  • 44 weeks
  • 53 weeks (around 12 months).

There is more information about each 'wonder week' - about what development stage may be happening during a 'wonder week' in the book by Vanderrijt, H. & Plooij, F. (2003)
The Wonder Weeks.   

Just as physical developmental stages do not stop when a child reaches 12 months of age, mental developmental stages will also continue, and there will continue to be 'good' weeks and more difficult weeks. Any parent of a teenager will be able to confirm that they still are having good and bad weeks.

Predicting 'sunny' weeks

The 'sunny' weeks can also be more or less predictable. The 'sunniest' weeks tend to happen around

  • 6 weeks
  • 10 weeks
  • 13 weeks (around 3 months)
  • 21 weeks
  • 31 weeks
  • 39 weeks
  • 49 weeks
  • 58 weeks.


Even though 'wonder' weeks can seem like difficult times when babies are clingy and unhappy, they are very special weeks because the babies are making a new big step forward.


Richter, J. & Woolmore, A. (2004).  Regressive Periods, Maternal Depression and the Development of Insecure Attachment.  Paper presented to WAIMH World Congress, Melbourne, Australia. Jan .

Rijt-Plooij, H.H.C. van de & Plooij, F. X.  (1992) Infantile Regressions: Disorganisation and onset of transition periods. Journal of Reproductive and Infant Psychology. 10, 129-149.

Sadurni, M. &  Rostan. C. (2002) Regression Periods in Infancy: A Case Study from Catalonia. The Spanish Journal of Psychology. Vol 5, No. 1, 36-44.

Vanderrijt, H. & Plooij, F. (2003) The Wonder Weeks.  Living Control Systems Publishing. 

Website: 'The wonder weeks' http://www.thewonderweeks.com/ 

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The information on this site should not be used as an alternative to professional care. If you have a particular problem, see a doctor, or ring the Parent Helpline on 1300 364 100 (local call cost from anywhere in South Australia).

This topic may use 'he' and 'she' in turn - please change to suit your child's sex.

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