Sleep regressions at 4 months

Do you know what happens to your baby's sleep when they turn 4 months? Let us help you manage these changes.

What is happening to your baby?

Unexpectedly, almost from one day to the next, your baby’s sleep will begin to be different, increasingly waking up at night, even every hour, napping for less time and finding it quite difficult to fall asleep

The outcome: your baby is much fussier and nights can lead the whole family to desperation. Many 4-month-old babies’ sleep patterns begin to show change and this is the time when the well-knownsleep regressions occur..

What are regressions?

A sleep regression is a period of time when a baby who’s been sleeping well suddenly starts waking a lot at night, has trouble falling asleep, or is unsettled at nap time.

We don’t like talking about regressions because these changes are mainly developmental. Rather, they are “progressions”. There are negative connotations to the very word regression: babies are not going backwards in their development but on the contrary are experiencing positive change in their growth.

What happens at 4 months?

In just three months babies have gone from sleeping and eating on a 24-hour cycle making no distinction between day and night to experiencing major changes in their biological sleep rhythm

On the one hand, babies are now starting to produce enough melatonin to foster the formation of circadian sleep-wake cycles, i.e. they will be able to tell between night and day, their sleep pattern is therefore maturing and will to some extent begin to resemble that of adults.

Babies will thereafter have different sleep stages and cycles lasting between 45/50 minutes, with a short awakening or awake-time at the end of each one linking it to the next.

These micro-awakenings are to blame for this “Regression”. Imagine your baby falls asleep in your arms or while breastfeeding and is then put in the cot after falling asleep. When the baby wakes up between sleep cycles to find that both the setting and his or her circumstances differ from those he or she was in at the beginning of the night, the baby is likely to wake up completely and need your help to go back to asleep, and again and again through the night…. Just the thought is exhausting and living through this can prove unbearable over time.

How to detect the 4-month regression

  • Baby’s appetite changes
  • Night-time awakenings increase
  • Crying and fussiness increases
  • Naps are shorter

Why does it happen?

  • REM sleep decreases
  • N-REM increases
  • The duration of the sleep cycle increases
  • Their brain is able to stay awake longer
  • The total number of daily sleep hours decreases

What to do

  • Stick to bedtime schedules, starting no later than 8:00 pm. This will help your little one’s biological rhythm to adjust.
  • Monitor and note how long your little one is awake and don’t let them oversleep their sleep windows
  • You can start building structured pre-bedtime routines

When does it start and when does it end?

The 4-month regression does not start immediately when babies are four months old and may dos so as early as at 3 months old. It all depends on each baby’s sleep maturity so remember that no baby is the same.

Regressions usually last from 2 to 6 weeks but that depends on how they are handled and on structured sleep schedules and routines being established.

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