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Why do babies startle in their sleep and How can you help them?
A baby’s sleep can feel unpredictable and difficult to understand, especially in the first months of life. Rhythmic breathing, facial expressions that change within seconds, tiny sounds and, sometimes, a sudden startle that wakes the baby — and you along with them.
It is a moment that naturally raises a question, especially for new parents: what is actually happening?
The answer lies in the way a newborn’s nervous system is developing and in the natural stages of baby sleep. Once you understand these, it becomes easier to understand what you can do to support calmer, deeper, more restful sleep — for both your baby and you.
What Is the Moro Reflex and Why does It happen?
The Moro reflex is one of the first reflexes a baby is born with and is, essentially, an inherited survival mechanism rooted deep in human evolution.
When a baby suddenly feels as though they have lost balance or is startled by something, the nervous system triggers a rapid response: the arms open wide, the fingers stretch out, the head moves backwards, followed by a closing motion, almost as if the baby is trying to hold on to something.
This reaction can be triggered by sudden stimuli: a loud noise, an unexpected movement, a change in light or even the sensation of falling that babies may experience when transitioning between sleep stages.
The Moro reflex is present from birth and usually begins to fade around the age of three to six months, as the central nervous system matures and the baby gains better control over their body.
Why do babies startle in their sleep? What is actually happening?
To understand why babies startle in their sleep, it is important to understand what their sleep looks like.
Unlike adults, babies spend more time in active sleep, also known as REM sleep: Rapid Eye Movement sleep. This is a lighter stage of sleep, during which the brain is highly active: it processes the day’s experiences, strengthens neural connections and may even produce dreams.
During REM sleep, a baby may show a wide range of signs: eye movements, facial expressions, smiles, small sounds and, of course, sudden startles. Because deep, quiet sleep represents a shorter part of a baby’s total sleep time, even a small stimulus can lead to a partial waking or a reflex reaction.
In the first months of life, the myelin sheath that protects nerve fibres is also not fully developed. As a result, nerve signals are less regulated, which makes reflexes more intense and more difficult for the baby to control.
Baby sleep stages
A baby’s sleep is organised into shorter cycles than an adult’s, lasting around 45 to 60 minutes in the first months. Each cycle includes:
Active sleep, or REM sleep, is the stage in which the brain is working intensely. The baby may move, make sounds and startle. This is also the stage in which the Moro reflex can be triggered most easily.
Quiet sleep, or non-REM sleep, is the stage of deeper rest. Breathing becomes more regular, the body relaxes fully and startles are less common. This stage is essential for growth and physical recovery.
Transitions between sleep stages are the most vulnerable moments. A baby may partially wake and, if they cannot settle back to sleep, they may cry. This is why the quality of the sleep environment matters so much: temperature, surrounding sounds and, above all, the physical sensation offered by the cot.
How you can help your baby sleep more peacefully
There are a few proven practices that can help reduce startles and support more restful sleep, both for your baby and for you.
Swaddling is one of the oldest methods used to soothe babies. It works precisely because it limits the arm movements triggered by the Moro reflex. A gentle, comfortable swaddle recreates the feeling of safety experienced in the womb. It should be used carefully, following your paediatrician’s guidance, and stopped once the baby begins to roll over independently.
Consistent background noise can help mask sudden environmental sounds that may trigger startles. A gentle fan sound or dedicated white noise app can make a noticeable difference in sleep quality.
A sleep routine helps the baby’s nervous system anticipate rest. A warm bath, a gentle massage, the calm voice of a parent and a peaceful atmosphere before bedtime all send clear signals that it is time to relax.
The recommended room temperature for baby sleep is between 18 and 20°C. A room that is too warm can disrupt sleep and increase nighttime restlessness.
Avoiding sudden stimuli means being mindful of bright lights, unexpected noises and quick movements near the sleep area, especially during the first months.
The sleep environment matters more than you think
Beyond routines and techniques, there is one factor many parents underestimate: what touches the baby’s skin while they sleep.
A newborn’s skin is three to five times thinner than an adult’s skin. Tactile receptors are extremely sensitive, and any unpleasant sensation, however subtle, can become a stimulus that interrupts sleep. Synthetic materials, chemical dyes or stiff fabrics can create a constant feeling of discomfort, which a baby can only express through restlessness and frequent waking.
This is why choosing cot bedding is not merely an aesthetic detail. It is a decision that can directly influence the quality of your baby’s rest.
Natural materials such as organic cotton, Merino wool and natural silk have properties that genuinely support sleep. They help regulate temperature, absorb moisture, feel gentle on the skin and create the soft, comforting sensation a baby can perceive even during deep sleep.
At Valeria Home, the baby product range is designed precisely from this perspective: carefully selected, non-toxic, plastic-free materials, made in Romania and certified according to OEKO-TEX® STANDARD 100 — an international standard which guarantees that every fibre has been tested for harmful substances.
The Merino wool pillow is a concrete example of a product created to support healthy baby sleep. Merino wool has a naturally fine structure that actively thermoregulates: it keeps warmth in when needed and helps cool the body when temperatures rise. The sensation it offers is one of gentle support, without rigidity — exactly the kind of comfort a baby in active sleep can benefit from.
The organic cotton bedding set completes the sleep environment with a breathable material that is soft to the touch and kind to sensitive skin. Organic cotton contains no pesticides or harsh chemical finishes, which means the only thing your baby feels is the natural, airy texture of the fibre.
When should you consult a doctor?
Startles during sleep are, in most cases, completely normal and tend to become less frequent with age. However, there are a few situations in which it is recommended to speak to your paediatrician:
- The startles are extremely frequent and intense, even after the age of six months.
- The baby cannot calm down after waking and cries for a prolonged period.
- There are rhythmic, repetitive jerking movements that resemble seizures.
- Sleep is severely fragmented and visibly affects the baby’s well-being during the day.
A parent’s instinct is a valuable guide. If something does not feel right, consult a specialist.
Good sleep begins with thoughtful details
The first months of life are a period of intense adjustment, both for babies and for parents. Fragmented sleep, startles and nighttime restlessness are all part of this stage, but that does not mean there is nothing you can do to improve your baby’s rest.
Gentle routines, a warm and peaceful environment and high-quality natural materials that feel good against the skin can make a real difference. Not an immediate or spectacular one, but a steady and meaningful difference, just like every carefully made choice.
If you are at the beginning of this journey and looking for products thoughtfully designed for your baby’s sleep, you can explore the Valeria Home baby range and choose what feels right for your little one.
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