It happens almost overnight.
For the last few weeks, you felt like you were finally turning a corner. Your baby was sleeping for four, maybe even six-hour stretches. You started to feel human again. You confidently told your friends, “She’s such a good sleeper!”
And then, suddenly, your baby is now waking up every 45 minutes. Naps are a disaster. Bedtime is a battle. You are exhausted, confused, and wondering what you did to “break” your baby.
Congratulations – you have simply hit the 4-month sleep regression. It is a rite of passage for almost every parent, and while it is brutal, it is actually a sign that your baby is developing perfectly.
Here’s everything you need to know to survive these sleepless nights and come out the other side with a better sleeper.
What’s actually happening?
First, a reframe: It shouldn’t be called a “regression.” It is actually a progression.
Newborns sleep differently than adults. They drift in and out of deep sleep easily. But around the 4-month mark, your baby’s brain is maturing permanently. Their sleep patterns are shifting to mimic adult sleep cycles.
Adults sleep in cycles of roughly 90 minutes. We go from light sleep to deep sleep and back to light sleep. Between these cycles, we actually “wake up” slightly. As adults, we roll over, fluff the pillow, and go right back to sleep without remembering it.
The Problem: Your 4-month-old is now cycling through these light and deep sleep stages, but when they hit that “wake up” point between cycles (every 45 to 90 minutes), they don’t know how to go back to sleep yet.
Signs you are in it
- Frequent night wakings: Specifically every 1-2 hours.
- Short naps: The dreaded “crap nap” that lasts between 30-45 minutes,
- Appetite changes: Distracted eating during the day, leading to “reverse cycling” (wanting to eat all night).
- Fussiness: General irritability due to overtiredness.
4 steps to better sleep
While this phase is temporary, it is also the perfect time to build healthy sleep foundations. Here’s your plan of action.
1. Master the sleep environment
Now that your baby is more alert, they are easily distracted. If the room isn’t conducive to sleep, they won’t settle.
- Pitch black: Darkness stimulates melatonin. Invest in high-quality blackout curtains.
- White noise: A sound machine drowns out household noise (dogs barking, doorbells) and mimics the constant whooshing sound of the womb, which is calming.
2. Watch the “wake windows”
A 4-month-old can only stay awake for about 90 minutes to 2 hours at a time. If they stay awake longer, their body produces cortisol (stress hormone) and adrenaline. This gives them a “second wind,” making it much harder to fall asleep and stay asleep.
- The fix: Watch the clock. If your baby woke up at 7:00 AM, they should be back in the crib for a nap by 8:30 or 9:00 AM, even if they don’t look tired yet.
3. Drowsy but awake
This is the hardest part, but it is the key to fixing the regression.
If you rock your baby all the way to sleep and then transfer them to the crib, they are asleep in your arms. When they wake up 45 minutes later in a cold crib, they panic. Imagine falling asleep in your bed and waking up on the front lawn – you’d start screaming too.
- The goal: Put them down when they are heavy-eyed and calm, but still slightly awake. They need to fall asleep in the space where they will wake up.
- The practice: It won’t work perfectly the first time. Try shushing or patting their chest while they are in the crib rather than picking them up immediately.
4. Separate eating from sleeping
At this age, babies are incredibly efficient eaters. They often don’t need to eat every 2 hours at night for hunger, but they do it for comfort.
- The shift: Try to move the last feeding to the start of the bedtime routine (feed, bath, book, bed) rather than feeding them to sleep. This helps break the association that “food = sleep.”
How long does it last?
The acute phase of the regression typically lasts 2 to 6 weeks.
However, because the change in their sleep architecture is permanent, the “waking up every hour” habit might stick around if you don’t work on independent sleep skills.
You are in the trenches right now, and it is okay to feel frustrated. It is okay to cry. It is okay to order takeout because you are too tired to cook.
But remember: This is happening because your baby’s brain is growing at an incredible rate. They are becoming more aware of the world. Stick to your routine, keep the room dark, and give them the space to learn how to connect those sleep cycles.
You will sleep again. We promise.
