4-month sleep regression: Signs, causes, and how long it lasts (2024)

Those first few months of your newborn sleeping through the day and waking up at all hours of the night are finally over, and they seem like they're getting the hang of sleeping more regular hours. Then, suddenly, your baby resists going to bed, wakes up throughout the night, and won't go down for naps – this is the 4-month sleep regression.

At 4 months old, your baby is ready to take the first of many massive developmental leaps. However, changes in their awareness of the world around them and shifts in their sleep pattern can disrupt their established sleep schedule, triggering a regression that keeps them (and you) up at all hours.

While your baby might not be sleeping through the night by 4 months, most babies have at least made steps toward sleeping for longer stretches by now. So when your little one suddenly starts sleeping less, it's easy to feel discouraged or as if you're doing something wrong. But don't worry – sleep regressions are temporary, and you can take steps to get your baby back to sleeping soundly.

(And for more in-depth information about sleep regressions, as well as how to combat them, check out Baby Sleep 101Opens a new window from BabyCenter Courses.)

What causes the 4-month sleep regression

If your little one's sleep changes have you scratching your head in confusion, you're not alone. Several factors contribute to sleep regressions, rather than one specific reason. Here's a look at some of the most common causes of the 4-month sleep regression.

• Sleep cycle changes. Newborns only have two sleep stages: REM (rapid-eye movement) and non-REM. But around 3 months, their sleep cycle starts to change and look more like an adult's, with four sleep stages (three of these are types of non-REM sleep, and the fourth is REM). This is typically why babies start sleeping for longer stretches, but cycling through these different stages can also cause them to wake up and struggle to fall back asleep as they get used to the new pattern.
• Developmental leaps. Babies generally become more aware of the world around them at this age. This means a baby who previously slept through anything might become more sensitive to light, noise, and changes in their routine. They could also be distracted by newfound skills like rolling over and other developmental accomplishments.
• Illness and discomfort. If your baby has been sick, feeling crummy might contribute to changes to their sleep routine. And while most babies' first teeth come between 6 and 10 months, your baby may start teething early – and that discomfort can disrupt their sleep.
• Changes in routine. Taking a trip, missing a few naps, or staying up later than usual can temporarily disrupt your baby's sleep routine. Any recent changes to your established routine could contribute to the 4-month sleep regression.

4-month sleep regression signs

At 4 months old, babies need about 15 hours of sleep in a 24-hour period. While there's some variation from child to child, you can generally expect this to play out as nine to 10 hours of sleep overnight, along with four to five hours of daytime sleep spread over three naps.

A sign that your baby is in a sleep regression is they're not getting the recommended amount of sleep for their age. More specifically, if you've noticed a shift in your baby's sleep patterns resulting in more night waking, difficulty falling asleep for naps and bedtime, waking up fussy, or waking shortly after putting them down, these could be signs your little one is in the throes of a sleep regression.

Outside of recommended benchmarks for the hours of sleep they should get, how can you tell if your baby isn't getting enough sleep? An overtired baby may resist going to sleep. They're often fussy throughout the day and more difficult to calm down. Young babies might fall asleep while eating or refuse to nurse altogether.

Other clues like redness around the eyes, yawning, looking away from stimulating things, and lack of interest in people or their environment can also tip parents off that their child isn't getting enough sleep.

How long does the 4-month sleep regression last?

Since each baby is different, it's difficult to say how long you can expect the 4-month sleep regression to last. However, the most important thing to remember is that it's temporary and will pass with time.

Generally, sleep regressions can last for a few days or up to a few weeks. However, a sleep regression that doesn't resolve and is accompanied by poor eating, poor weight gain, inadequate dirty diapers (babies typically wet their diapers four or five times a day), or failure to meet developmental milestones is cause for concern. These combined symptoms suggest that underlying medical problems might be contributing to poor sleep.

While most sleep regressions don't require a medical checkup, if a regression lasts longer than four weeks, or if your baby has other symptoms you're worried about, check in with their pediatrician. They can help figure out if another issue is keeping your baby from sleeping well.

Once you're over the 4-month sleep regression hurdle, look out: Regressions can happen any time, but especially at 6 months, 8 months, 12 months, and 18 months.

How to cope with the 4-month sleep regression

When your baby doesn't sleep, life is a challenge! It might feel as if you'll never get good sleep again. The good news is that sleep regressions aren't permanent, and your baby will eventually sleep well again. In addition to practicing patience, here are a few tips for coping with the 4-month sleep regression.

• Establish a routine. If you haven't already, now's the time to adopt a daily routine for predictable nap times and bedtimes. Staying consistent, even when things aren't going well, is one of the most beneficial things you can do for your baby's sleep during a regression.
• Try sleep training. Most experts recommend sleep training when your baby is between 4 and 6 months old, so this is the perfect time to try. There are a few methods to teaching your baby how to fall asleep on their own: cry it out, fading, gentle, and the Ferber method.
• Wean off nighttime feedings. Between 4 and 6 months old, most babies get enough calories during the day and can go through the night without eating. If you think your baby is ready, talk to your baby's pediatrician and try to wean them off their night feedings over about two weeks.
• Track feedings. While your baby might be developmentally ready to sleep through the night without eating, first make sure they're eating enough during the day to make this work. If you think your baby might be waking up because they're hungry, keep track of when and how much they eat, and make adjustments to ensure they're getting enough calories during the day. Find out how much breast milk and formula 4-month-olds need.
• Create a calming environment. Increased awareness of the world around them can make sleep a boring prospect for a baby. Help them get back to sleeping soundly by addressing outside noise, putting a sound machine in their room, and perhaps putting up blackout curtains. Make bedtime soothing by keeping things quiet and calm and avoiding screens and stimulating toys before sleep.
• Separate night and day. Because newborns so often sleep around the clock, it may require a habit switch to teach them the difference between night and day. During the day, keep things bright, noisy, and playful. As bedtime approaches, draw the blinds and quiet the house as much as possible.