I have so many clients and friends talk to me about wonder weeks, and how their child is going through a leap and this is affecting their sleep.
Firstly, yes babies and toddlers absolutely go through developmental milestones, but to think that all babies and toddlers will hit these milestones in the same order at the same time is not true. You may notice periods of change in your childs behaviour, but relying on ‘wonder weeks” as your guide can actually just make your anxiety about child development worse, as you expect your child to meet all of these milestones at the exact time that the book/app suggests, and also miss cues for why your child is actually being fussy, clingy, grizzly etc.
The book was first published nearly 30 years ago, and the author of the Wonder Weeks book, Frans Plooij, continues to push it, even though it was proven to be false. One of the author’s PhD students actually did a follow up study to try and find evidence of these leaps, and found absolutely no scientific evidence supporting his claims. Both behaviour and cortisol levels were tested and failed to find any evidence of greater fussiness or higher cortisol levels corresponding to the leaps. Plooij actually tried to prevent the British Journal of Developmental Psychology from publishing the study. Another co-worker of the Wonder Weeks author described Plooij’s behaviour as “very indecent” and that the book contradicts a greater body of research on child development. It therefore, comes as no surprise that Plooij was actually fired and left academia.
There is some value in Wonder Weeks if you choose to follow it, but please don’t rely on it as Gospel. If you have any concerns about your childs development, please consult your doctor, and certainly not Wonder Weeks.
Here is one example of a website that shares my same views, and another good read.