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Digging into The Wonder Weeks

Have you ever woken up to the sound of a crying baby for the third time in the night and thought to yourself, “That’s it. This week, I’m taking some action. This week we’re going to do something about this.”

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, this is probably just a phase, or you get into the, “I knew what I was getting into when I decided to have a baby,” mindset. Or you start googling “sleep regressions” and read that if your child isn’t sleeping well it’s because they are approaching a developmental milestone and you stumble across The Wonder Weeks.

For those of you who aren’t familiar with it, The Wonder Weeks is almost like a Farmers Almanac for babies. It was developed by the husband-and-wife team of Frans Plloji, a behavioral scientist, and Hetty van de Rijt, an educational psychologist.

If you are not familiar with The Wonder Weeks, here is the basic premise: Starting at five weeks old and continuing on until 20 months old, babies go through 10 mental development stages or “leaps”. These leaps, according to the book, take place at very specific points in a baby’s first 20 months of life.

During “sunny weeks,” baby is typically happy and agreeable. These are followed by “stormy weeks,” during which baby is fussy and inconsolable due to the neurological development taking place. Then comes the “wonder week” where the new skill is finally mastered and baby goes back to being “sunny” again.

Many, and I mean many parents absolutely swear by this book and the popular 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 to the day as opposed to the week.

Others will tell you that the science it’s built on is flawed, and what the authors are doing is essentially a form of pediatric astrology. They are making predictions based on norms and averages, reassuring parents that good things are just over the horizon.

Let’s start with some facts. The 1992 study[1] that The Wonder Weeks is founded on used a sample size of 15 participants and relied almost exclusively on questionnaires filled in by the mothers (as opposed to direct observation from the researchers). Dr. Plooij’s argument for the small sample size stated 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”.

In the mid 1990s, Dr. Plooij’s Ph.D. student, Dr. Carolina de Weerth, attempted to replicate the findings[2] from the original study with a smaller sample size of four babies. She failed to reach the same conclusions. Dr. de Weerth claims that Plooij pressured her to find correlations that supported his original research. When she refused, he attempted to prevent the publication of her findings. Plooij’s contract with the University of Groningen wasn’t renewed following the incident, and he left academia altogether.

All of that to say, there’s still controversy and debate over its legitimacy. But that’s not anything new when it comes to the world of parenting, is it?

If you take comfort in being able to predict when your baby will be cranky, I say go for it! Follow The Wonder Weeks and allow it to give you reassurance and confidence in your baby’s development. I completely understand the difference it makes when your baby is extra fussy one week and you can open the app and see that they are supposed to be fussy that week! It can even release anxiety and allow you to relax in the midst of a hard week. Parents need all the support they can get, and your mental health is so important!

But there is a downside to The Wonder Weeks.

You may find that your child doesn’t precisely follow their predictions and develop unnecessary concerns that your child is not developing on schedule. In a world where we already compare our baby’s development to everyone else’s, we don’t need one more pseudo measure of healthy development. Don’t forget, the study was based on inaccurate research with a total of 15 babies.

The concern I have with The Wonder Weeks is that it gives parents a reason not to prioritize their baby’s sleep. (Sleep, by the way, is one of the most important factors in our baby’s development in the first place!)

If your baby is going to be encountering developmental leaps for the first 20 months of their life, when it is the right time to make good sleep a priority? Do you need to wait until they have made it through some of the milestones? If so, which ones? If every behavior can be “explained”, when will a parent feel affirmed in their decision to make a change, to begin helping their child get consolidated night sleep?

Let me be very clear with you. Outside of a diagnosable health issue, there is absolutely no “wrong time” to teach your baby to sleep well. Yes, teaching an infant healthy sleep habits will certainly look different than teaching a 2 year old to sleep through the night. But they are both appropriate times to teach healthy sleep habits. Any age is!

Right before a “sunny week,” right at the tail end of a “stormy week,” or smack dab in the middle of a “wonder week,” are all perfect times to get started. There’s no developmental milestone, no specific week, no time in a baby’s life that could be considered the wrong time to get them sleeping well.

By the way, this philosophy is not controversial among medical professionals. They will all agree that adequate sleep is essential to the health and well-being of everyone in the family unit, and that teaching your baby some independent sleep skills is safe and effective, whether it’s week ten or week fifty.

Practically, there are times that I will tell parents to hold off for a day or a week, say if they are going on a vacation or have something out of the ordinary going on. But knowing that your child has an upcoming milestone is never a reason to delay helping your child develop sleep skills.

Whether you take stock in The Wonder Weeks or not, we can all agree on the fact that our children are always developing, week after week, month after month. Your baby will actually handle these changes even better if they are getting the sleep they need!

[1]Hedwig H.C. Van De Rijt-Plooij PhD & Frans X. Plooij PhD (1992) Infantile regressions: Disorganization and the onset of transition periods

[2] Weerth, C. D. (1998). Emotion-related behaviors in infants: a longitudinal study of patterns and variability. s.n.


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