How Many Brain Cells Does a Newborn Have?
A newborn baby has an estimated 100 billion brain cells, or neurons. This is the same number of neurons that adults have, but the newborn’s brain is much less developed. The neurons are not yet connected to each other in the way they will be as the baby grows and develops.
During the first few years of life, the neurons in a baby’s brain form connections with each other, called synapses. This process is known as neuronal development and it is essential for learning and memory formation. As these connections form, the number of neurons remains constant, but the complexity of the connections increases.
The newborn’s brain continues to grow rapidly during infancy and early childhood. By age three, a child’s brain has reached 80 percent of its adult size. During this time, new neurons are created and existing ones become more complex. By age five, a child’s brain has nearly doubled in size from when they were born.