Everything to Know About the 4 Month Sleep Regression

Any parent dealing with four month sleep regression will tell you it’s no laughing matter. Here, experts break down everything you need to know.
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Updated September 25, 2023
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Baby is finally sleeping through the night, you have naps down to a science and you’re finally feeling a little bit like your old, rested self again. But just as you’re celebrating baby’s fourth month of life, something happens to bring you right back down to reality: Your sleeping beauty is back to their former partying ways, waking up multiple times throughout the night. What gives? It’s called the four month sleep regression, and it’s here to ruin the good thing you’ve got going on. Fortunately, it doesn’t last forever. Below, experts break down what to know about this stage and how to get through it.

What Is the 4 Month Sleep Regression?

Four-month sleep regression is one of the “fine prints” of parenting you don’t pay attention to it until it happens to you. It “refers to a set of sleep challenges that arise in babies around the age of 4 months old, even if they were sleeping well previously,” says Jillian Thistel, a certified pediatric sleep consultant and founder of Twinkling Stars Pediatric Sleep Consulting in Ontario, Canada. “These sleep challenges often seem to happen suddenly, leaving parents confused about what’s happened to their great little sleeper.” In a nutshell, the four month sleep regression can “reduce the total amount of sleep babies (and parents) are getting per day,” adds Elizabeth Cilenti, MD, MPH, a pediatrician with Northern Virginia Family Practice. Moreover, despite its name, the four month sleep regression can start even earlier (i.e. at 3 months) or later, (i.e. at 5 months). In fact, sleep regressions can actually keep popping up throughout babyhood and childhood, Cilenti adds.

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What Causes 4 Month Sleep Regression?

The 4-month-old sleep regression leaves many parents bewildered. The most common cause behind baby’s four month sleep regression is biological changes in sleep cycles. Newborns experience two stages of sleep: active (also known as REM) and quiet sleep, Thistel explains. “As babies get close to the four-month mark, they start to develop their circadian rhythm, hormones such as melatonin, and their stages of sleep mature and start functioning like adult sleep cycles.” Essentially, this means baby now experiences four different stages of sleep, and they start to spend more time in non-REM, notes Cilenti. It can take some time for babies to get used to this change, resulting in disrupted sleep routines and the dreaded four month sleep regression.

Another culprit behind baby’s four month sleep regression? Baby’s physical and cognitive development, including hitting new milestones and growth spurts. The four month sleep regression may be taking a toll now, but it’s ultimately a good thing. “It’s a normal part of the process of growing,” Cilenti says. Occasionally, changes to routines and environments, as well as illness can also cause disrupted sleep, she adds.

So will all babies experience the four-month sleep regression? While most babies do experience these biological sleep cycle changes, not all will be impacted by it in the same way. “Some little ones may experience a whole range of sleep challenges, while others may hardly experience sleep disruptions,” Thistel says.

4 Month Sleep Regression Signs

Wondering how to spot those four month sleep regression symptoms? Most of the signs of four month sleep regression deal with sudden sleep challenges, so you’ll be able to tell pretty quickly if baby is experiencing this stage. “These signs can seem to start out of nowhere, even for babies who were sleeping well previously,” Thistel says. According to Thistel and Cilenti, some of these four-month sleep regression signs include:

How Long Does the 4 Month Sleep Regression Last?

Once baby kicks into four month sleep regression mode, the big question is: How long does it last? As we know, all babies are different, and how long sleep regression lasts will vary depending on your baby and their particular sleep situation. Cilenti says the four month sleep regression may last anywhere from a few days to a few weeks.

However long the phase, Thistel encourages parents to use it to help baby build healthy sleep foundations and habits—such as learning how to self-soothe—to help get them through the sleep disruptions. You might be tempted to change baby’s sleep schedule, but she encourages parents to resist this urge. “Focusing on solid sleep foundations and consistency is key,” she adds.

4 Month Sleep Regression Tips: How to Get Through It

Once you realize baby is going through the dreaded four month sleep regression, your parental instincts to solve the problem shift into high gear, and you might be desperate for some four month sleep regression tips. Don’t worry, there are things you can do to help baby and save your sanity. For how to get through four\ ] month sleep regression, check out these tips from Cilenti and Thistel:

  • Establish a consistent bedtime routine: Babies thrive off having a regular bedtime and naptime routine, Cilenti says—and she advises parents to start baby on a sleep routine before the four-month mark. Use baby’s wake windows and sleepy cues—yawning or rubbing their eyes—to help determine baby’s bedtime and routine schedule. Incorporating things like a bath, story, bottle and bed can all help baby know what to expect and when. Keep in mind, baby’s regular schedule may be disrupted during the four month sleep regression. You may wonder if you should shift their schedule, but following their sleepy cues is still a great way to ensure they’re going to sleep at the right times rather than getting overtired, notes Thistel.
  • Make baby’s room dark: Get baby to associate darkness with sleep. This means making sure baby’s room is dark, quiet, calm and free of screens and other distractions when it’s time to go to sleep, Cilenti says. If baby wakes up in the middle of the night, they’ll realize it’s still dark and time to sleep.
  • Put baby to bed while sleepy but awake: If you’re giving baby a bottle or breastfeeding and notice they’re getting drowsy, it’s best to put baby to bed rather than wait until your infant is totally passed out. It helps them learn how to self-soothe and get to sleep without your help. “It’s a skill babies need to practice in order to learn,” says Cilenti.
  • Give baby a few minutes if they wake up: Similarly, don’t rush to baby right away if they wake up in the middle of the night, advises Cilenti. Instead, she says to give baby a few minutes to self-soothe (as long as there’s no emergency), and see if they can fall back asleep on their own. If you do go to them in the middle of the night, make sure it’s all business. Try not to turn the lights on and talk to baby too much to help them understand it’s time to sleep rather than time to wake up.
  • Focus on baby’s overall health: The lack of predictable sleep patterns may be frustrating during the four month sleep regression stage, but Thistel says to keep focused on ensuring baby’s properly fed, learning and practicing new skills during the day and otherwise healthy and happy. This is also a great time to practice different ways that are effective in soothing and calming baby, she adds.
  • Be kind to yourself: “It takes years for children’s sleep cycles to develop, and they don’t fully mirror adult patterns until they’re around 5 years old,” Cilenti says. What’s more, changes to sleep won’t be linear, may be hard to predict and will often be beyond parents’ control. That said, sleep deprivation can take a real toll on your own well-being. “Make a plan for how to take care of yourself, and remember to give yourself some extra self-compassion during these sleep regressions,” she says. Above all else, know this is just a phase, and baby will move past it eventually.

When to See a Pediatrician About 4 Month Sleep Regression

While four month sleep regression is usually nothing to worry about, Thistel says there are a few signs that warrant a call to your pediatrician, including if baby is:

  • Experiencing discomfort or pain
  • Snoring or mouth breathing while sleeping
  • Sick or parents believe baby might be sick
  • Baby has a fever or appears to be waking up from pain, which could be sign of an ear infection
  • Losing any previously achieved milestones

Along with these symptoms, Cilenti encourages parents to reach out if they’re worried about baby’s feeding and growth, or have any concerns regarding baby’s development overall. “I’ve had parents bring in the baby worried that they’re missing an ear infection, thinking that there must be something [wrong because] baby’s suddenly waking up every two or three hours crying,” she says. “Just having your pediatrician check over baby, and knowing that they look healthy and are growing well can give you peace of mind and help you to sleep better.”

Thistel agrees: “If a parent suspects that something more is going on for their little one, I always encourage them to trust their instincts. It’s always important to consult their doctor or pediatrician to rule out any medical issues or other potential challenges that may be impacting sleep.”

The good news is that 4-month-old sleep regression doesn’t last forever, and eventually it’ll pass. The four month sleep regression may disappear as quickly as it came on, or fade slowly, Cilenti says. In any case, you’ll know the sleep regression has passed when baby starts to go back to their usual and more predictable sleep patterns. While there are more developmental milestones just around the corner waiting to create their own havoc, for now try to sleep tight and don’t let the four month sleep regression bug bite!

Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.


Elizabeth Cilenti, MD, MPH, is a pediatrician with Northern Virginia Family Practice. She completed her medical degree and residency at Indiana University School of Medicine and her master’s degree in public health at the Harvard T.H. Chan School of Public Health.

Jillian Thistel, is a certified pediatric sleep consultant in the Greater Toronto Area in Ontario, Canada. She is a member of the Association of Professional Sleep Consultants and founder of Twinkling Stars Pediatric Sleep Consulting.

Learn how we ensure the accuracy of our content through our editorial and medical review process.

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