The first years of a child’s life are extremely important, starting from the first trimester of pregnancy. The 6 stages of brain development that happen in the first three years have lifelong impacts.


Neurons and synapses are brain structures that help different parts of your brain communicate. They take chemical signals, transport them, and form new wiring within your brain. The work that neurons and synapses do lays the foundation for learning, memory, and other brain functions.

When you’re born, you have all the neurons that you’ll have for your entire life. It’s the synapses that encourage development in your brain. Your first few years of creating these connections will determine the abilities you have later on in life.

Before a child turns three, they’ll have almost double the number of synapses that they’ll have later on as adults. Synapses are created at such a high rate during early childhood that your brain will end up making more than you actually need. Synapses are strengthened as you use skills or are exposed to things repeatedly.

For example, if as a child you were constantly surrounded by people talking, the synapses in language-related parts of your brain were often activated. This repeated activation strengthened them until you learned how to speak for yourself. This is proof that your life experience and environment make huge contributions to the development of the brain.

First trimester

A few weeks after a baby is conceived, the brain begins to develop. For about eight weeks, the basic structures of the brain form. The neural tube is formed. This slowly becomes the brain and spinal cord. Around seven weeks after conception, the first neurons and synapses are developed in the spinal cord.

These first connections allow movements in the womb so small that an ultrasound or MRI can pick them up, but a mother cannot feel them. As there is more movement, the brain continues to develop. Movements become more coordinated as the weeks go on.

Second trimester

During the second trimester, gyri and sulci are formed. Gyri are the ridges, bumps, and indentations that make up the topmost layer of the brain. They increase the surface area of the brain, meaning that more neurons can fit and more information can be processed.

Sulci are the grooves on the surface of the brain that surround the gyri. They help divide the brain into different sections, like lobes and hemispheres. Sulci also add more surface area to the brain. Together, gyri and sulci allow the brain to do more without making the brain too big to fit into the skull.

While gyri and sulci form, synapses start to develop in new areas of the brain. A layer of myelin starts to form to help the brain process information more quickly.

Third trimester

Towards the end of pregnancy, the brain takes on new responsibilities as it prepares for birth. Reflexes like fetal breathing develop and the brain starts to respond to external forces like touch, pain, vision, smell, taste, and sound.



First year

During the first year of life, a baby's brain develops quickly. The ability to develop motor skills quickly increases and limited vision turns into a more perfect vision. Around three months, a baby starts recognizing things, and their capacity to remember gets better.

During this year, the parts of the brain that support language and speech abilities are greatly strengthened by surrounding language use. After a few months, a baby is able to tell the difference between their native language and a foreign language.

Second year

More language skills are acquired during your second year of life. More synapse connections are made in the brain’s language areas result in a growing vocabulary. Research shows that between a baby's first and second birthday, the number of words they know will quadruple.

More myelin in the brain means that a baby can take on more complex tasks and carry them out faster than before. These more demanding abilities include self-awareness. During this stage, a baby becomes more aware of self, emotions, and intentions. The baby will start using their own name, will recognize their reflection in the mirror, and say words like “I” and “me”.

Third year

Synapse creation will peak during a baby's third year. Various areas of the brain are strengthened and brain ability greatly improves. During this year, a child will develop a more clear understanding of past and present events and cause and effect.

Brain development

As a child, a baby is born ready to learn! Healthy growth comes from their surroundings and repeated exposure to new things. The six stages of brain development build on each other. They form essential brain connections to support you throughout your life.

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Medically Reviewed on 10/4/2021
First Things First: "Brain Development."

Simply Psychology: "Gyri and Sulci of the Brain."

The Urban Child Institute: "Baby's Brain Begins Now: Conception to Age 3."