Why Do Babies Cry in Their Sleep? Common Reasons Explained
Ever been jolted awake because your sweet sleeping baby started to whimper, sob, or full-on wail with eyes completely shut? The experience can be more than a little unsettling. Don’t worry, it is completely normal. Babies cry in their sleep because of immature sleep cycles, hunger, discomfort, or active REM sleep, and most of the time, it resolves on its own within a minute or two.
Because babies spend far more time in light, active sleep than adults, their brains are busy processing and developing all night long. That activity shows up as sounds, movements, and yes, crying. Understanding what is behind it can make those middle-of-the-night moments a lot less stressful.
- Babies cry in their sleep because of immature sleep cycles, hunger, discomfort, or active (REM) sleep.
- It is usually normal. Most crying resolves on its own within a minute or two.
- Newborn sleep problems are common and tend to improve with age.
- There are clear signs that tell you when to step in and when to wait.
- Knowing your baby's patterns makes it easier to tell normal from concerning.
- Why Do Babies Cry in Their Sleep?
Babies do not sleep the way adults do. Their sleep cycles are shorter, around 50 to 60 minutes, compared to 90 minutes for adults, and they spend far more time in REM (active) sleep. According to the National Sleep Foundation, newborns need between 14 and 17 hours of sleep per day, with much of that time spent in active, light sleep stages.
During REM sleep, the brain is busy. It is processing the day, consolidating memories, and developing rapidly. This is when you will see:
- Fluttering eyelids
- Twitching limbs
- Facial expressions like smiles, frowns, and grimaces
- Whimpering or crying sounds
This is called infant sleep behavior and is a sign of a healthy, developing brain, not distress.
The transition between sleep cycles is also a vulnerable moment. Babies briefly surface into lighter sleep, and if they have not yet learned to settle themselves, that is often when the crying starts.
What Are the Common Reasons Babies Cry in Their Sleep?
Try treating the problems below before you start to worry!
Hunger
This is the most common reason, especially in the early months. Newborns have tiny stomachs and need to feed frequently, around every 2 to 3 hours. Even older babies may stir and cry from hunger during the night.
Signs it is hunger-related:
-
Rooting or sucking motions while crying
-
Crying that escalates if not addressed
-
The last feed was more than 2 to 3 hours ago
Sleep Cycle Transitions
As babies move between sleep stages, they partially wake. Many will cry briefly, sometimes for just 30 to 60 seconds, before drifting back off. This is one of the most common reasons babies wake at night and usually requires the parent to do nothing. If it is happening very regularly, it may be worth reading about why your baby wakes every 2 hours to rule out other causes.
Active (REM) Sleep
During active sleep, babies process emotions and sensory experiences. Brain activity can trigger sounds and movements that appear distressful but are not. Your baby is essentially reacting to their dreams.
Discomfort
Physical discomfort is a common but overlooked trigger. Things like:
- Gas or trapped wind
- A wet or dirty nappy
- Being too hot or too cold
- Teething pain (in older babies)
The NHS notes that discomfort from gas is especially common in babies under three months, when the digestive system is still maturing.
Overtiredness
A baby who was put to bed too late or did not nap well during the day will often have a more disrupted night. Overtired babies produce more cortisol, which makes it harder to stay in deep sleep and easier to cry between cycles. This can overlap with sleep regressions, which are another common cause of increased night waking.
Newborn vs. Older Baby: Does Age Change Anything?
Yes, why do babies cry in their sleep as they grow? Here is a general breakdown:
|
Age |
Common Causes |
What Usually Helps |
|
0 to 3 months |
Hunger, gas, REM sleep activity |
Feeding, burping, swaddling |
|
3 to 6 months |
Sleep cycle transitions, mild discomfort |
Brief wait before responding |
|
6 to 12 months |
Teething, separation anxiety, and overtiredness |
Comfort settling, consistent routine |
|
12 months and up |
Dreams, developmental leaps, routine disruption |
Reassurance, predictable bedtime |
Newborns cry more frequently simply because their sleep architecture is more fragmented. According to Nationwide Children's Hospital, most babies do not start sleeping through the night until at least 3 months of age, with some not managing it until closer to 12 months. For a full breakdown, see when babies sleep through the night.
How Do I Know if the Crying Is Normal or Something to Be Worried About?
Most sleep issues in babies are developmental and resolve on their own. But it helps to know the difference between what is normal and what is worth a closer look.
|
Normal Sleep Crying |
Worth Investigating |
|
Brief (under 2 minutes), self-resolves |
Crying that escalates and does not stop |
|
Occurs during sleep cycle transitions |
Accompanied by fever, vomiting, or rash |
|
Baby settles without fully waking |
Baby seems in pain and is inconsolable |
|
Happens occasionally |
Sudden change from established sleep pattern |
|
No other symptoms present |
Difficulty breathing or unusual sounds |
If your baby's crying is accompanied by any of the "worth investigating" signs, contact your paediatrician. Trust your instincts. You know your baby best.
How to Respond Without Disrupting Sleep
One of the most common mistakes parents make is rushing in too quickly. Because infant sleep behavior during REM and cycle transitions is so active, intervening immediately can actually wake a baby who would have settled on their own.
A few helpful approaches:
Wait 1 to 2 minutes before going in. Many babies resettle without any help.
- Observe before acting. Watch for escalation rather than reacting to the first sound.
- Keep night interactions calm and quiet. Use low light and minimal stimulation.
- Avoid picking up immediately if the baby is not fully awake. Try a gentle hand on the chest first.
- Stick to a consistent bedtime routine. Predictability helps babies feel safe and self-settle over time. If your baby relies on feeding or rocking to fall asleep, it may be worth looking at how to get your baby to sleep without rocking or feeding.
The NICHD (National Institute of Child Health and Human Development) recommends responding to your baby's needs while also helping them develop their ability to settle independently as they get older.
Understanding Your Baby's Sleep Is the First Step to Better Nights
Baby suddenly crying while they’re sleeping is one of the most common concerns new parents have, and one of the least talked about in practical terms. The good news is that most of the time, it is your baby's brain doing exactly what it should: growing, processing, and developing.
Knowing the common causes, from hunger and discomfort to sleep cycle transitions and active REM sleep, helps you respond with confidence instead of anxiety. And knowing when to wait versus when to step in makes those night wakings feel a lot more manageable.
Keep Your Baby Comfortable Through Every Sleep Stage
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Frequently Asked Questions
Q. Why do babies make noises while sleeping, even when they are not crying?
Babies are naturally noisy sleepers. Grunting, squeaking, and sighing are all common during active REM sleep as the brain processes the day. It is completely normal and usually nothing to worry about.
Q. Should I pick my baby up every time they cry at night?
Not necessarily. Wait a minute or two first. Many babies self-settle without any help. If the crying escalates or they seem genuinely distressed, then go to them.
Q. Can babies have nightmares?
Possibly, but it is not confirmed. Babies have very active brains during REM sleep, which can produce unsettling sensations. There is no solid evidence of nightmares in very young infants.
Q. Is it safe for babies to sleep on their side?
No. The NHS and most health organisations recommend placing babies on their back to sleep for every sleep until they are 12 months old. This significantly reduces the risk of SIDS.
Q. Will my baby grow out of crying in their sleep?
Most likely, yes. Sleep cycles lengthen as babies mature and their ability to self-settle improves. Many parents notice a shift around 6 months, though every baby is different.
Sources
- How Much Sleep Do You Really Need? - A National Sleep Foundation article on the amount of sleep people need and how it varies by age.
- Soothing a crying baby - NHS guidance on what to do with a crying baby.
- What are the sleep patterns of a newborn? - A Nationwide Children's Hospital article on how newborns normally sleep.
- Infant Care and Infant Health - A detailed factsheet on infant care by the National Institute of Child Health and Human Development
