TL;DR
At around 4 months, your baby’s sleep changes dramatically. This phase is called the 4-month sleep regression, and it happens when your baby’s brain matures and starts forming adult-like sleep cycles. Night wakings, short naps, and early mornings are normal, but they do not last forever. Calm routines, consistent sound, and patience help your baby adjust to this big developmental leap.
5-Point Summary
- The 4-month sleep regression is a normal developmental stage, not a setback.
- It is caused by changes in brain development and sleep cycles.
- Symptoms include frequent night waking, short naps, and fussiness.
- Consistent routines and calming sensory cues help babies adjust faster.
- This phase usually lasts 2 to 6 weeks before sleep improves again.
What Is the 4 Month Sleep Regression
The 4-month sleep regression is when your baby suddenly stops sleeping the way they used to. They may wake more often at night, fight naps, or cry when laid down. It often feels like their sleep has fallen apart overnight, but in reality, it is a sign of healthy development.
The Sleep Foundation explains that around 3 to 5 months, babies’ brains mature, moving from newborn sleep patterns to more structured cycles that include light, deep, and REM sleep. As a result, they wake fully between cycles instead of drifting back to sleep automatically.
Why It Happens
During this stage, your baby is learning to connect sleep cycles on their own. They are also more aware of their surroundings, which can make falling back asleep harder. Add in growth spurts, teething, or increased appetite, and it is easy to see why rest becomes tricky.
A study published in Sleep Medicine Reviews found that these early developmental changes in sleep organization are linked to neurological growth, memory processing, and sensory development (ScienceDirect). In short, your baby is learning new skills, and their sleep patterns are catching up.
Common Signs
- Frequent night waking
- Shorter naps than usual
- Fussiness or crying before sleep
- Early morning wake-ups
- Increased hunger or feeding at night
The American Academy of Pediatrics notes that frequent waking at this stage is temporary and part of learning to self-soothe.
How to Get Through It
1. Keep Your Routine Consistent
Babies thrive on repetition. Try to keep nap and bedtime routines the same every day. This stability helps their body recognize when it is time to rest. Even a simple order like feed, cuddle, lullaby, lights out can anchor your baby’s rhythm.
2. Create a Calm Sleep Environment
Dim lighting, a comfortable temperature, and soft, steady sound help babies transition between sleep cycles more smoothly. Research shows that white noise helps infants fall asleep faster and stay asleep longer (PubMed).
Many parents use sound companions like Lullabear to maintain the same gentle rhythm each night without screens or bright lights. The consistent sound becomes a cue that it is time to sleep, even when routines are disrupted.
3. Respond with Comfort, Not Panic
It is normal to soothe your baby when they wake, but try to keep interactions quiet and brief. Speak softly, pat gently, and avoid turning on bright lights. Over time, this teaches your baby to settle back into sleep with minimal stimulation.
4. Watch Wake Windows
At 4 months, most babies can stay awake for about 90 to 120 minutes before needing rest. Missing that window can lead to overtiredness, which makes settling harder. Observe your baby’s cues such as zoning out or rubbing eyes and start the wind-down before they are overtired.
5. Take Care of Yourself Too
This stage can be exhausting. Try to rest when your baby naps, share night shifts when possible, and give yourself grace. Sleep regressions test every parent, but they always pass.
How Long It Lasts
Most babies move through the 4-month regression within two to six weeks. The key is consistency. Once your baby adapts to their new sleep cycles, they often sleep more deeply than before.
Takeaway
The 4-month sleep regression is a milestone, not a mistake. Your baby’s brain is developing, their patterns are changing, and they are learning new skills. Stay calm, keep routines predictable, and use familiar cues like soft sound to guide them back to rest. Whether it is your voice, gentle rocking, or a sound companion like Lullabear, consistency and comfort are what help babies find their rhythm again.