Developmental Leaps & Unhappy Babies

Do you suddenly have a fussy baby or one that is crying unusually at bedtime? Is their once cheerful demeanor suddenly grumpy and clingy? Are they resisting naps that they previously took without a problem?

They might be in a wonder week!

What is a wonder week? Wonder week periods are not always a week long (despite the label). However, they are periods of developmental growth where your baby’s brain is expanding to process and achieve new things. After a wonder week, your baby will likely begin to exhibit new awareness or skills (ie. rolling over, saying a word, grabbing a toy). However, getting through a wonder week can create a fussy baby and be a taxing and very frustrating experience.

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What are some signs that your fussy baby is in a wonder week?

These are a few of the wonder week signs that we observed with our baby girl:

Your fussy baby won’t go to bed at night

If you’ve been sleep training your baby and they’ve been relatively consistent with easily going down to bed at night, then a sudden inability to do so could indicate that a wonder week is at hand. We kept our daughter on a very structured routine and began sleep training at an early age (you can read more about her newborn schedule here), so it was odd and extremely frustrating when she suddenly became hysterical at bedtime and wouldn’t console herself. As much as it was against my overall sleep training goals, I often had to nurse our fussy baby daughter to sleep during wonder weeks since there was no other way to calm her down.


Baby is suddenly very fussy throughout the day

Developmental leaps, or wonder weeks, can sometimes be easy to confuse with growth spurts. Sometimes they do overlap. However, if your baby is suddenly extremely fussy during the day and doesn’t seem to want or need more food, it may be a sign of a wonder week. Our daughter was generally a content baby during the day as long as she was well fed and we maintained her sleeping schedule. However, when wonder weeks hit she would become quite the fussy baby and downright inconsolable at times. It was as if every sight and sound overstimulated her. It became very difficult to calm her down and getting her to nap well became more difficult as a result.

Your fussy baby is suddenly very clingy

We probably observed this sign least in our baby girl, but there were moments during the wonder week periods where I saw it. Our independent little daughter was never a clingy baby. However, during her developmental leaps it seemed that she needed more comfort and nearness to mommy to keep her calm.


Are you having trouble getting your baby to sleep through the night? Read also:

7 Tips to Get Your Baby Sleeping Through The Night


How do I know when to expect a fussy baby from developmental leaps?

All of the above signs can help you confirm whether your baby is experiencing a wonder week, but you don’t have to rely on them alone to know if you are in the thick of one!

There is an official Wonder Weeks book that can offer far more extensive information from real credible sources explaining what the wonder weeks are and how to detect them. However, my favorite way to stay in the know with our daughter’s developmental leaps was by using the The Wonder Weeks App.

Using the Wonder Weeks app saved me a shred of sanity throughout our baby’s first year as the periods of fussy mental growth came and went.

A few features we loved in the app include:

  • A calendar of when to expect your baby’s wonder weeks to hit

You can enter your child’s due date into the app and it will generate a week by week calendar to show you when to expect your baby to hit the fussy wonder week periods. It uses “cloudy skies,” “thunderstorm skies,” and “sunny skies” to exhibit when your baby will be fussy, extremely fussy, or happy.

  • Explanations of new skills to expect after wonder weeks

Each time our precious daughter hit a wonder week and became a difficult and fussy baby we found it intriguing to check the app to see what kind of new skills might result from the leap she was in. The app included detailed information about what she was learning that was making her brain so overstimulated and details of what pieces of that we might see once she settled down. Very often as soon as the fussiness of her wonder week ended we would see some of the exact skills mentioned in the app emerge!

I highly recommend using the Wonder Week app. I am one mom who saved a small piece of sanity by using it.

If you are in the middle of a wonder week with your little one, the bad news is that there is no magic answer to ease your fussy baby’s demeanor or make bedtime a smooth and happy experience.

However, the good news is that it will end! Some of the leaps are longer than others, but take heart that your baby’s new inconsolable demeanor will not be their ongoing normal if they are in a leap. Whenever our daughter hit a wonder week period I found some solace in knowing that the sleep training we had worked so hard to achieve was not lost for good when I had to nurse her to sleep in those phases. After she got through each leap she generally went back to maintaining the habits we had worked on before it.

I know not every mom embraces the wonder weeks or agrees that their child follows the schedule of them in the book and app, but I was so glad that I discovered wonder weeks and the app! Our daughter seemed to follow the schedule in the app very closely and it brought me comfort to know that the periods of sudden fussiness had a reason behind them and that they wouldn’t last forever. If you or your child are similar to me, then I hope that hearing about our experience with developmental leaps can at least provide you with a piece of comfort as well. If the wonder weeks don’t seem to line up with your baby’s fussiness or provide any answers, then I hope you are able to get to the bottom of your fussy baby before you go too crazy!

Hang in there mommy! Your exhaustion and tears are worth it and things will get easier to manage!

wonder weeks, developmental leaps, baby suddenly fussy, baby suddenly won't sleep

Maintaining a nap and bedtime schedule saved our sanity with our baby girl’s sleep! If your baby isn’t sleeping through night or you’re wondering what a schedule for their age group looks like check out my post with sample first year baby schedules.

Developmental Leaps & Unhappy Babies