A newborn baby has about 270 to 350 bones in her body. As the baby grows, some of the bones, such as those in the skull, fuse together. This is why, after people grow into adults, they only have 206 bones in their bodies.
The skull of a baby is actually made of three bones. This is important because these bones can move around to make childbirth possible. The baby is also born with cartilaginous bones that ossify as they grow. This means the cartilage is replaced with bone material. Besides the bones of the skull fusing together, bones in the spinal column and long bones also fuse.