A fetal skeletal system contains over 300 bones. These bones are made almost exclusively out of soft cartilage and eventually fuse into an adult skeleton.
In order for a baby to successfully pass through the birth canal, its skeletal structure must not be rigid. The cartilage of a fetal skeleton gradually forms into bone as the child ages via a process called ossification in which healthy bone material is grown in the body.
When a baby is born, it has over 300 cartilage-based bones in its skeletal system. When new bone material is grown in the body, many of these bones fuse together to form the adult skeleton, which contains 206 bones.