Newborns shiver, twitch, and jerk during sleep primarily because their nervous system is still immature. In the vast majority of cases, these movements are completely normal and not a sign that anything is wrong. They look alarming, but they actually serve an important developmental purpose, helping your baby’s brain build connections between its sensory and motor systems.
That said, there are a few situations where shivering-like movements deserve closer attention. Here’s how to tell the difference.
Sleep Twitching Helps Build the Brain
During REM sleep (sometimes called “active sleep”), motor areas in your baby’s brain generate brief, jerky movements in the face and limbs. These twitches are not random noise. They trigger activity in the spinal cord, sensory and motor brain regions, and the hippocampus, which is involved in memory and learning. Researchers at the University of Tübingen describe these twitches as “self-stimulation,” providing sensory feedback to the brain at a time when it’s disconnected from the outside world. This feedback helps the brain tune and advance the wiring of sensory and motor systems without the distraction of external stimuli.
Newborns spend far more time in active sleep than adults do, which is why you see so much movement. Tiny facial grimaces, fluttering eyelids, jerky arm and leg movements, and what looks like shivering are all part of this process. It can happen dozens of times during a single sleep cycle.
Why Newborn Movements Look So Jerky
A newborn’s nervous system is not fully insulated yet. The protective coating around nerve fibers (called myelin) that allows smooth, controlled signals hasn’t finished developing. One theory is that spinal cord circuits responsible for dampening muscle reflexes are still immature, leading to an exaggerated stretch reflex. This is why even a minor signal can produce a visible tremor or shudder. As these circuits mature over the first few months, the jerkiness fades and movements become smoother.
The brain pathways that normally suppress movement during sleep are also underdeveloped. In adults, a chemical signaling system involving serotonin keeps your muscles still while you dream. In newborns, these serotonin pathways in the brainstem haven’t matured, so movements that would be blocked in an older child or adult slip through freely.
Benign Neonatal Sleep Myoclonus
There’s a specific, well-studied condition called benign neonatal sleep myoclonus that causes rhythmic, repetitive jerking during sleep. It typically starts in the first two weeks of life and looks remarkably like a seizure, which understandably frightens parents. The jerking can involve the arms, legs, or whole body, and it happens only during sleep.
The key feature: it stops when the baby wakes up. It also doesn’t cause any arousal response, meaning your baby sleeps right through it. Researchers believe a temporary serotonin imbalance and genetic factors contribute to the condition. The majority of cases resolve on their own by 3 months of age, and it has no effect on development or long-term health. No treatment is needed.
The Moro Reflex Can Look Like Shivering
The Moro reflex, sometimes called the startle reflex, is another common source of shivering-like movements during sleep. It follows a distinctive pattern: your baby’s arms suddenly extend outward, then curl back in toward the chest in a bowing motion. A sudden noise, a change in position, or even the baby’s own breathing pattern can trigger it. Studies show that a spontaneous arousal sequence during sleep often starts with a deeper breath, followed by a startle, and then a brief moment of wakefulness.
This reflex is present in all healthy newborns and typically fades between 3 and 6 months. Swaddling can reduce how often the Moro reflex disrupts sleep, since it limits the sudden arm extension that tends to wake babies up.
Could Your Baby Actually Be Cold?
True shivering from cold is actually uncommon in very young newborns because their shivering mechanism isn’t well developed yet. Babies rely more on a special type of body fat (called brown fat) to generate heat. Still, if the room is too cold, your baby can experience cold stress, which shows up differently than adult shivering.
Signs of cold stress include skin that feels cold to the touch, blotchy or mottled skin coloring, and unusual quietness or listlessness. On darker skin tones, color changes may be easier to spot on the palms of the hands or soles of the feet. The recommended room temperature for a baby’s sleeping environment is 68 to 72°F (20 to 22°C). A good rule of thumb: dress your baby in one more layer than you’d find comfortable, and check the back of their neck or their belly to gauge warmth rather than relying on their hands and feet, which tend to run cool naturally.
How to Tell Tremors From Seizures
The most practical test parents can do at home is simple: gently hold the shaking limb or give your baby something to suck on. Normal tremors and twitching will stop when you restrain the limb or when your baby begins sucking. Seizures will not. A seizure continues regardless of touch or repositioning.
Other red flags that suggest something beyond normal twitching:
- Timing: The jerking happens while the baby is awake, not just during sleep.
- Duration: A single episode of rhythmic jerking lasts more than 10 seconds.
- Eye movements: You notice unusual eye rolling, fixed staring, or repetitive eye fluttering during the episode.
- Feeding changes: Your baby has become difficult to feed, has a weak or unusually high-pitched cry, or seems increasingly lethargic between feedings.
Low Blood Sugar and Jitteriness
One medical cause of tremors in newborns worth knowing about is low blood sugar, or hypoglycemia. It’s more common in babies who are premature, small for gestational age, or born to mothers with diabetes, but it can happen in otherwise healthy newborns too. Jitteriness and tremors are among the earliest and most visible symptoms.
Other signs that accompany low blood sugar include poor feeding, a weak or high-pitched cry, low body temperature, unusual sleepiness, and in more serious cases, changes in skin color toward a bluish or pale tone. Most hospitals screen at-risk babies in the first hours after birth. If your baby was sent home and you’re noticing persistent trembling combined with feeding difficulty or unusual sleepiness, that combination warrants prompt medical evaluation. Prolonged or severe low blood sugar in newborns can affect brain development, but when caught and corrected early, outcomes are typically excellent.
When the Shivering Will Stop
For the vast majority of newborns, sleep-related twitching and tremoring peak in the first few weeks and gradually decrease as the nervous system matures. Most benign sleep myoclonus resolves by 3 months. The Moro reflex fades between 3 and 6 months. General jitteriness from nervous system immaturity improves steadily over the same timeframe. By the time your baby is 4 to 6 months old, you’ll notice far fewer jerky movements during sleep, though occasional twitching during REM sleep is normal at any age.