4-Month Sleep Regression: Signs, How Long It Lasts and What Helps

What is the 4-month sleep regression?

The 4-month sleep regression is a period, typically around 4 months of age, when a baby who previously slept well suddenly starts waking often at night or struggling to nap, according to Karitane, a parenting service in New South Wales, Australia. Karitane links it to several changes at this age, including a burst of brain activity, rapid growth, more awareness of surroundings and a baby's sleep moving from newborn patterns toward more adult-like cycles of light and deep sleep, which may bring lighter sleep and more frequent waking.

A newborn's sleep begins in active sleep rather than quiet sleep, according to a 2022 review of 93 studies in the Maternal and Child Health Journal, and by six months all sleep should begin in non-REM sleep.

The American Academy of Pediatrics (AAP) says babies do not have regular sleep cycles until about 4 months of age. Cleveland Clinic says that as babies get older, their sleep cycles through deep and light phases, more like an adult's, and adjusting to the lighter phases can make them more likely to wake up for a bit.

Age	What changes in sleep	Source
Newborn	Sleep begins in active sleep rather than quiet sleep	2022 review
After 2 months	Active sleep becomes REM sleep, and quiet sleep becomes non-REM sleep	2022 review
Around 2 to 4 months	The body clock (circadian rhythm) begins to develop	BASIS
About 4 months	Regular sleep cycles appear	AAP
3 to 5 months	The 4-month sleep regression can start anywhere in this range	Karitane
By 6 months	All sleep should begin in non-REM sleep	2022 review
At least 12 months, often later	The body clock is fully established	BASIS

Is the 4-month sleep regression really a regression?

BASIS, the infant sleep information service of the Durham Infancy and Sleep Centre, says the term "sleep regression" has no biological basis, so by its account the 4-month sleep regression is not a regression at all: renewed waking is part of how babies grow and learn. BASIS adds that babies who begin sleeping for longer periods early on may start waking again later, often because of normal developmental changes.

Karitane says that while the word regression can sound negative, the phase marks a positive and important stage of development in a baby's sleep cycles and brain growth.

BASIS also says that although parents may hear babies should start sleeping in longer stretches around three to four months, research shows this happens in only about 1 in 3 babies. The majority still wake between sleep cycles, day and night, according to BASIS.

What are the signs of the 4-month sleep regression?

Signs of the 4-month sleep regression include frequent night waking, shorter naps, increased fussiness, changes in feeding habits and needing more help to fall asleep, according to Karitane. Cleveland Clinic names the most obvious sign as a baby suddenly waking up more often at night.

Cleveland Clinic pediatrician Heidi Szugye, DO, says not to assume a sleeping issue involves a regression, because a baby may wake for many reasons, including an illness, a dirty diaper or a grumbly tummy. Karitane adds that babies may wake more from increased hunger as their bodies grow rapidly, which can easily be mistaken for sleep regression.

How long does the 4-month sleep regression last?

Most babies move through the 4-month sleep regression within a few weeks, though timing can vary, according to Karitane. Cleveland Clinic, writing about sleep regressions in general rather than the 4-month one, says they typically last a week or two before children get back on track.

The sleep development behind it carries on much longer. BASIS says a baby's body clock is not fully established until at least twelve months, often later, and that babies' sleep patterns mature over the first several years of life. The 2022 review notes that occasional sleeping through the night did not prevent later night waking. For the sleep totals researchers observe in younger babies, see how much sleep a baby needs at each age.

Can the sleep regression happen at 3 or 5 months?

Yes: Karitane says the 4-month sleep regression typically happens at around 4 months but can start anywhere between 3 and 5 months. Cleveland Clinic says the timing of sleep regressions varies by child, and that other regressions can coincide with growth spurts and developmental milestones throughout a baby's first year.

Sleep is already changing before four months: the 2022 review describes rapid changes in sleep structure within the first 12 weeks, and BASIS says the body clock begins to develop at around two to four months. Why a one-month-old doesn't know it's night covers the weeks before that.

Later milestones can unsettle sleep again: the 2022 review cites studies in which infants who were crawling between 5 and 8 months had more disrupted sleep than their pre-crawling peers.

What helps with the 4-month sleep regression?

The general sleep advice of the AAP, the Canadian Paediatric Society (CPS) and BASIS, none of it written for the 4-month regression specifically, covers a consistent bedtime routine, putting your baby down drowsy but awake, a few minutes' pause at night, enough daytime naps and protecting your own sleep.

At bedtime

The AAP advises putting babies 4 months and older to bed when they are drowsy, without waiting until they are asleep, so they learn to fall asleep on their own. In its advice for babies up to 4 months, the CPS also says to put your baby in bed drowsy but awake, and that it is okay to cuddle and rock a baby until they are drowsy.

The CPS calls a consistent bedtime routine important and says many parents like the "3 Bs": bath, book, bed. Cleveland Clinic suggests avoiding screen time and energetic play before bedtime.

At night

In its advice for babies up to 4 months, the CPS says babies will stir during the night and suggests giving them a few minutes to try to settle on their own before going to them. For babies 4 months and older, the AAP advises not rushing in to soothe a crying baby, while noting you can still feed them, change a dirty diaper or comfort them if they are sick. BASIS describes frequent night waking as a biologically normal part of infancy.

During the day

In its advice for babies up to 4 months, the CPS says an overtired baby has more trouble sleeping and that napping helps a baby sleep better at night. By 4 months, most babies need three naps a day, in the morning, afternoon and early evening, according to the CPS; wake windows by age covers how long babies typically stay awake between them. BASIS suggests regularly exposing your baby to daylight during the day to support sleep consolidation.

For you

BASIS suggests accepting that sleep disruption is a normal part of looking after babies, and prioritizing your own sleep where you can. On sleep training, BASIS reports that studies including babies under 6 months found small or non-existent practical outcomes that wore off after a few weeks, though BASIS adds that, across sleep training research overall, there is good evidence it can improve parental mood disorders.

If you feel you are not coping, Karitane suggests placing your baby in their crib and leaving the room for a moment; your baby will be safe while you calm yourself.

If your baby is swaddled, the AAP says to stop swaddling as soon as they show any signs of trying to roll over. The rest of a safe sleep space is in safe sleep practices.

When should you call your pediatrician?

Call your pediatrician if your baby can't seem to get past the sleep regression or something doesn't seem right to you, which is Cleveland Clinic's advice.

• Your baby regularly snores loudly or seems to stop breathing for a short time, then gasps. The CPS says this can be a sign of a problem.
• You feel you are not coping. Karitane says your physical and emotional wellbeing is at stake and that it is best to seek support.