Your Premature Baby, their Brain, and Why Sleep Matters for Growth and Development


 Lying on her side, her knees tucked up and close to her chest. Her arms midline with hands curled slightly under her chin. Her little head adorned with a pale yellow knit cap, keeping her warm. Her eyes sealed tightly closed have only opened a brief few times. Wires draped from her small fragile body, keeping a mechanical eye on her every breath, every move.

She is the face of prematurity. Like so many babies born too soon. This little girl was brought into this world 14 weeks early. A ventilator pushes air into her lungs, an incubator keeps her warm and safe, and the lights are dim to protect her from bright environment of the NICU. She looks perfectly formed in every way. From her cute little nose to her ten fingers and ten toes. But the most vulnerable part of her body, her brain, is still very much developing. Although we cannot see this complex system of neurons, the inner workings of this highway, and the pathways that connect them; we must be aware of their importance and actively engage in practices to protect their growing delicate development.

At 26 weeks gestation her brain is still in a critical period of rapid development, producing more than 50,000 neurons every second. These neurons are migrating outward and assembling pathways and connections that will later allow this little girl to walk, to talk, and to interact with her environment. Her brain is still being primed to see, smell, hear, taste, feel, and understand her world. All the connections that make these things happen are done in perfect rhythm and form while inside the protected environment of the womb, but being born prematurely they must now be done in the artificial and mechanical world of the NICU. Although every effort is made to replicate this perfect environment, it is practically impossible. The womb is a wet, warm, quiet, dark, and comfortable. The NICU environment is quite the opposite, with an overload of lights, sounds, and unfamiliar touch. We can, however alter some of our practices as healthcare providers and parents to allow for the best possible environment for brain growth and development.

The brain is one of the last organs to develop in the womb, but it is one of the most fragile. A fetus at 26 weeks gestation will sleep approximately 20-22 hours while in utero. Likewise, the baby born prematurely at 26 weeks should be sleeping and be engaged in an environment conducive to important brain developing sleep. The brain can only develop and form new neuro-pathways when it is sleeping. Sleep is essential to regulate body systems, store energy, and develop the senses (hearing, touch, taste, smell, and vision) correctly. It is during sleep that vital sensory information is being organized into permanent brain circuits, pathways, and connections.


During gestation, the sensory systems mature and gradually switch on. Think of this system as a dimming switch. As new neurons develop and form new pathways, they flicker on and off until they are fully formed and functioning. This is evident in a premature baby who is having periods of apnea and bradycardia. Their neurological system is still developing these pathways and sometimes forgets to “fire” and connect these signals. This gradually disappears as these neurons mature and perfect their pathways.

The brain grows at an amazing rate during development. Brain development occurs in three stages. Starting within hours of conception, organogenesis- the formation of the central nervous system (CNS)- occurs.

The second stage is marked by growth and formation of neurons and glial cells. Neurons are responsible for sending, receiving, and interpreting information from all parts of the body. Glial cells provide support and protection for neurons.

The final stage is a period of "pattern of formation" where neurons migrate and create cellular connections.

In the third trimester of pregnancy (after 28 weeks gestation), there is great brain activity involving complex maturation and wiring. The weight of the brain triples during the last thirteen weeks of pregnancy.

During the last trimester the two brain areas most important for cognitive process- the cerebral cortex and the cerebellum- undergo major changes.

The cerebellum controls movement, coordination, balance, and muscle tone. It is comprised of white matter and a thin outer layer of densely folded grey matter. The cerebellum contains hundreds of millions of neurons for processing data. It relays information between the body muscles and the areas of the cerebral cortex that are responsible for motor control.


The cerebral cortex is the thin layer of grey matter forming the outer surface of the brain. It consists of millions of neurons that are responsible for thinking, learning, and storing memories.

Underneath the grey matter is white matter, which consists of millions of axons. Axons carry electrical messages between neurons and into the spinal cord.

Deep within the brain are a series of chambers that are called ventricles.

The brain and the spinal cord are protected by a clear fluid, called cerebrospinal fluid, produced within the ventricles.

The germinal matrix is near the ventricles and makes new neurons and the cells that support them. The germinal matrix is a fragile "nest" of cells that become smaller as the baby matures, disappearing between 32 and 34 weeks gestation.

The cerebral cortex contains wrinkles and grooves that look like folds. These folds help the brain to function more efficiently and powerfully and are very important for learning and intelligence. This process rapidly takes place between 24 and 40 weeks gestation.  The cerebral cortex (the thinking part of the brain) almost double is size in the last few weeks of pregnancy.

At or before 23 weeks gestation, the brain has a smooth surface
At 24-26 weeks gestation, there are only a few shallow grooves within the cerebral cortex
At 27-29 weeks gestation, there is some depression and more groove formation
At 30 weeks gestation, there is an increase in the wrinkles and grooves in the cerebral cortex
At 33 weeks gestation, there is in-folding deep within the cerebral cortex
At 34 weeks gestation, the brain weighs only 65% of what the term baby's brain weighs. It also is only two thirds of the size, with many pathways, cells, and neurons still growing.

In the last trimester of pregnancy, as thousand of neurons continue to be produced every second, the brain starts to prune back the excess neurons, eliminating the cells and connections that are weak. This sculpting of neural pathways continues after birth and happens when the baby is sleeping and he brain is at rest. when a baby is born prematurely, all these things must now happen outside of the womb in an environment that is foreign to the developing neurological system.












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