What is the four-month sleep regression?

Just as you think you’ve figured out your baby’s sleep routine, she hits the four-month sleep regression and everything changes.

Well done: You’ve survived the first few months with a newborn, figured out when and how to breastfeed like a pro, and your little one is finally starting to sleep for longer stretches at night. Before you start celebrating, know this. At around the three, four, or even five-month mark, your baby’s sleep patterns will change, and you’re slap-bang in the middle of the “dreaded” four-month sleep regression your friends have warned you about.

The truth is, most babies hit the four-month sleep regression as it’s another milestone they need to reach, explains lead baby sleep consultant and founder of the Baby Sleep Site, Nicole Johnson. “For some babies, it’s very mild and brief, but for others, it’s a rough phase marked by lots of crying, frequent night waking, and disrupted naps,” she says.

A shift in sleep habits 

Simply put, the four-month sleep regression marks a permanent change in your baby’s sleep habits, says Nicole. It shouldn’t be called a regression as it’s more like a progression in terms of development, but it does alter a baby’s sleep patterns. This is because your baby’s brain is starting to mature, and she’s beginning to sleep more like an adult rather than a newborn who spends more time in the ‘”quiet”, deep sleep state. As adults, we all go in and out of light and deep sleep (also known as REM and non-REM sleep) – we turn over a lot, wake up for a drink of water, or feel startled after a bad dream, and this happens to babies too. However, the difference is that babies have shorter sleep cycles than adults – only around 45 to 60 minutes, which means your little one will stir or wake up after 45 minutes throughout the night (and during naps).

3 Reasons why sleep regression happens

  1. You are your baby’s only sleep association: The beginning of the night is your baby’s deepest sleep, and after this, she’ll cycle between light and deep sleep, explains Nicole. This means that if your little one needs you to help her fall asleep, whether it be feeding, singing, or rocking to sleep, she’ll continue to need your help throughout the night to fall back asleep after each sleep cycle. Babies also sleep the lightest between 4 am and 6 am, so this could also mean that you’re in for a very early morning wake-up if your little one won’t settle back to sleep at 4 am. This could lead to a disrupted night’s sleep for you and your little one.
  2. Your baby is starting to move more: Between the ages of four and six months, your baby’s mobility can start to cause sleep disturbances and tie into the four-month sleep regression. This often happens when your little one no longer wants to be swaddled, explains sleep expert Tracy Hogg in her book, Top Tips from the Baby Whisperer. Your little one might be starting to get up on her knees or push herself forwards in the bed – you might find her scrunched up in the corner of the cot, or she could constantly kick her blankets off, leaving her feeling cold and uncomfortable.
  3. She’s hungry or overtired: When a child goes through a growth spurt, it’s often fast and furious – your little one will gain weight and grow in height in just 24 to 48 hours, explains Dr Michelle Lampl, who is also a  growth researcher at Emory University in the US. This can also disrupt sleep patterns as she’ll be hungrier, thirstier, and generally fussier during this time. Over-tiredness (often caused by overstimulation or keeping your baby awake for too long between naps) can make sleep regressions worse. As parenting expert and author Meg Faure explains, “If a baby is already in an overtired state, it may be more difficult to get her to go to sleep and stay asleep.” The reason is that the body produces cortisol and adrenalin to stay awake and alert when fatigue hits, and this can cause a vicious cycle of being too tired to sleep.

Ways to cope 

“We always advise parents to get to the root of why the four-month sleep regression is causing such disruptions,” says Nicole. “Usually, negative sleep associations are to blame – babies who have become accustomed to being rocked, fed, or held to sleep continue to need their sleep associations. But now that their sleep patterns have changed, they need them all night long.” Before you panic, Nicole advises waiting a few weeks to see if your baby’s sleep improves. If it doesn’t, then it may be time to work on weaning your four-month-old from her sleep associations.

Expert tips

  • Stay consistent. Stick to your baby’s sleep routine during the day and night.
  • Provide a positive sleep environment – make sure your baby’s room is dark and cool, and use white noise such as a fan of music to help your little one fall back asleep between sleep cycles.
  • Make sure your baby has been well fed before each nap and night-time sleep.
  • If your baby is overtired, try to put her to sleep earlier at night and help her to nap longer during the day. This will help to reduce those stress hormones and ensure your baby gets the sleep she needs.
  • If your baby is four-months-old, keep her awake time to no more than two hours during the day and avoid overstimulation at all costs.

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