Rapid growth in the womb: By the last trimester of pregnancy, a fetus’s brain undergoes major increases in size, folding of the brain’s brain’s outer layer (cortex), and the development of connections between neurons.But there are some major trends in the construction and remodeling that take place: The process of brain development through childhood and into adulthood is far from straightforward, with change happening at different rates in different parts of the brain.
