Ever Wonder About “The Wonder Weeks?”

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Have you ever woken up to the sound of your crying baby and thought to yourself, “That’s it. This is the week I’m taking some action. This week we’re going to start teaching that baby some sleep skills.”

Then, sometime in the early morning when your second cup of coffee starts to kick in, you find yourself second guessing the idea. Maybe you feel like things aren’t that bad yet, or maybe someone told you that this wasn’t really the right time, since your baby was just about to go through a big developmental milestone, and makes a reference to The Wonder Weeks.

The Wonder Weeks is similar to a Farmer’s Almanac for babies. It was developed by husband-and-wife team of Frans Plloji, a behavioral scientist, and Hetty van de Rijt, an educational psychologist. 

The concept goes something like this: Beginning at five weeks old and continuing through the 20-month mark, babies go through 10 mental development stages or “leaps” as the authors refer to them. These leaps, according to the book, take place at very specific times in a baby’s life, starting at five weeks and continuing through the 20-month mark. 

During the “sunny weeks,” baby is typically happy and agreeable, followed by “stormy weeks,” during which baby’s fussy due to the neurological development, and then comes the “wonder week” where the new skill or development is mastered and baby goes back to being “sunny” again.

Many parents follow this book and use the companion app. (The original book has sold over 2 million copies across 25 languages.) Some people even claim that it tracks their little one’s development day-to-day as opposed to the week. 

The 1992 study that The Wonder Weeks is founded on, used a sample size of 15 participants and relied mostly on questionnaires filled in by the mothers as opposed to direct observation from the researchers. Dr. Plooij’s counter argument for the small sample size, stating that if you find a behavior in two individuals, “then you already have proof that the phenomenon exists and is not due to luck or chance,” doesn’t do much to shore up his credibility.

In the mid 1990s, Dr. Plooij’s Ph.D. student, Dr. Carolina de Weerth, attempted to replicate the findings from the original study with an even smaller sample size of four babies, and reached different conclusions. Dr. de Weerth claims that Plooij pressured her to find correlations that supported his original research, and when she refused, he attempted to prevent the publication of her findings. (A claim that Plooij denies.) Plooij’s contract with the University of Groningen wasn’t renewed following the incident, and he then left academia altogether.

In other words, there is still controversy over the legitimacy of The Wonder Weeks.  

If predicting when your baby will be cranky helps you through a prolonged period of crying to think, “This is just her developing as she’s supposed to,” then high fives all around. Parents need all the support they can get.

The potential downside I see is that parents might put too much stock in the accuracy of The Wonder Weeks, and develop some unnecessary worries if things don’t go according to schedule. Because if there’s one thing parents don’t need, it’s unrealistic expectations based on inaccurate research, telling them that their little one has failed to hit a developmental milestone exactly as the book or app has predicted.

At what point in a baby’s development should you start making sleep a priority?

Is it best to wait until after some of these developmental milestones have passed? 

If so, which ones? What will happen if we get started too early or too late?

Outside of a diagnosable health issue, there is absolutely no “wrong time” to teach your baby to sleep well.

I’m confident that pediatricians will agree with that statement. It is not controversial among the scientific community or medical professionals. We are all in agreement that adequate sleep is essential to the health and well-being of the whole family, and that teaching your baby some independent sleep skills is safe and effective, whether it’s week five or week fifty. 

There are situations where I will tell parents to hold off for a few nights, say if they’re going on vacation within a week or so, and I recommend that they get started on a night when they don’t have to work early the next day, as night one can be a little on the turbulent side, but you should never delay your plans to help your baby develop their sleep skills due to some kind of upcoming milestone. Those are going to keep on coming, day after day, week after week, and your baby will have an easier time progressing through them if they’re getting the sleep they need.


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