I absolutely love what I have learnt about 'wonder weeks' or developmental periods in babies. ( also called Infantile regressive periods) When I look back in diaries kept for my children I can identify these periods now I know more about them. - Babies brains arent 'hard wired' and research

shows they are continually having leaps in development. This has been recorded as increased brain activity associated with big changes in development and often associated unsettledness. Because these leaps can be difficult to handle  it is  shown that babiesin many cultures can have these predictable periods of fussiness. The recorded weeks are week 5,8,12,17,26,36,44,53. The weeks are adjusted according to whether your baby was premature or late. For example a baby born 2 weeks early would not experience the first wonder week till aged 7 weeks  and a baby born 1 week late may experience the first wonder week @ 4 weeks. Not all babies become fussy during and around that week some are able to handle the changes occuring in them easier  than others. Signs of it may be - crying more, going off food/milk at little, some babies who have been sleeping well may be harder to get to sleep, or may wake more frequently, some need more cuddles, and older babies may become more clingy. The baby may come out of these periods with a new skill you can see ie rolling, sitting, being more aware of faces, people,patterns etc or it may be a new perception for them an understanding of self or that some people are 'strangers' etc.

Of course there are other reasons for babies to become fussy  ie illness nappy rash etc, but I think it is great to have an understanding of these sorts of changes as it makes it a little easier to cope with a 'wonder week' when you know there is this great work being done. Its a welcome job to give babies the extra attention, cuddling needed during these periods knowing that things will eventually mellow out again.

If any one wants any more reading- some authors are H. Vanderrijt, F Plooij (book 'the wonder weeks'),  or articles by M. sadurni, C Rostan.(Journal of reproductive and infant psychology) J. Richter, A Woolmore ('Regressive Periods, Maternal depression and the Development of insecure Attachment - paper presented at WAIMH world congress)