This leap did NOT make much of a mark for William.
He was not at all extra fussy, and I would have simply described the time period as calm and quiet with not much going on.
Now that being said, I was focused on so many other things, so that might be why.
William was being switched from exclusive breastfeeding to full formula and bottles. He was not gaining enough weight, and we quickly determined that my supply was just not enough for him.
Not exactly a minor change.
He’d fallen off of the growth curve completely and, while he was a super happy baby and not complaining of being hungry, he was just not getting enough.
As soon as I started getting the formula in him, he chunked up nicely and was doing SO much.
He was talking more, laughing more, rolling more, etc. We halfheartedly joked about the fact that had I only been feeding him enough, he’d have been doing things things all along! Not exactly funny, but we’re trying to see the humor.
Read the full story about the switch from breastfeeding to formula here.
Right after the switch in diet, he also came down with pneumonia.
Needless to say, we were a bit distracted during leap 4.
As I went through the checklist below, however, a lot of changes did occur!

The Fourth Wonder Week
Leap 4 is known as wonder week 19, as it happens around week 19 of your baby’s life.
This fourth wonder week is known as “The World of Events”.
The way I understand leap 4 as described on page 110 of The Wonder Weeks book, is as follows:
Prior to this leap, your baby doesn’t see a whole “event” as a whole. He sees it in all of the little parts.
In order to grab a toy, he has to think about getting his hand to it, then opening his fingers, then grabbing the toy, then closing his fingers, etc.
After this event, he can grab the toy with his eyes shut if it makes contact with him. He understands the event as one whole series and can predict the outcome before it happens without having to break it down into a step by step process.
In fact, grabbing toys is a perfect example, because most baby’s will have mastered that after leap 4…

Wonder Weeks Chart (Leap 4)
Pages 122-125 in The Wonder Weeks book outlines a checklist of new skills that your baby might be learning. For more detailed information, check out the book! Here is our experience with each of the skills:
Body Control


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Grabbing, Touching, and Feeling

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Watching

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Listening

Talking

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Body Language

Other Skills
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Signs and Fussiness
There was NO extra fussiness this leap!
William’s naps were bliss, and his nighttime was amazing.
He sleeps 12 hours at night 7 pm to 7 am.
His naps are 9-11 am, 1-3 pm, and 5-6 pm. He sleeps for the entire nap 99% of the time and is well rested and happy.
He took to the huge change of switching to formula from exclusive breastfeeding very easily, and he even was happy throughout having pneumonia.
This leap was an easy one!
Frequently Asked Questions About Leap 4:
Leap 4 is the fourth developmental leap in your baby’s life. It occurs around week 19 of their life, which is why it is referred to as wonder week 19.
Your baby will master big “events” during this leap. He/she will be able to grab things without looking if it comes into contact with the object. He/she will be able to hear someone, look for them and find them easily. These events happen as a whole now instead of in small bits and pieces.
The World of Changing Sensations
-Responds more to touch
-Looks at things longer
-Smiles for the first time
-More alert
-Notices odors

The World of Patterns
-Turns head toward sounds
– Sits forward on lap
– Touches toys
– Discovers parts of body
– Looks at interesting
things
– Makes more sounds
– Holds head up easily

The World of Smooth Transitions
– Follows with eyes
– Turns head smoothly
– Rolls from tummy to back
– Shakes rattle
– Finds things funny
– Enjoys light
– Enjoys sound fluctuations

The World of Events
– Very active
– Grasps well
– Puts your hand in his mouth
– Responds to name
– Uses more consonants
– Reacts to mirrors
– Searches to find you
– Pushes food away when done
– Gets frustrated and impatient
The World of Relationships
– Shows interest in people
– Focused on details
– Lifts things
– Imitates sound
– Protests if you walk away
The Stormy Period
Baby discovers “distance” and realizes that Mama can walk away and leave.
The World of Categories
– Understands words
– Recognizes himself
– Starts to try crawling
– Exaggerates moods
– Plays peek-a-boo
The World of Sequences
– Answers questions
– Points
– Repeats games
– Imitates gestures
The World of Programs
– Grabs clothes
– Puts things away
– Bathes doll
– Observes what you do
(cooking, eating, getting ready)
The World of Principles
– Practices facial expressions
– Wants to do things independently
– Thinks ahead
– Temper tantrums
– Understands mine and yours
– Negotiates
– Irrational fears
The World of Systems
– Increase in word comprehension
– Sense of time
– Learns rules of what belongs to who
– Understands extended family
– Can console others
– Shows their independence and “power” over themselves