You had more bones at birth.
Adults have 206 bones, which makes about 15 percent of their overall body weight. Newborns, on the other hand, have 300 bones. Those bones are changing shape and growing day by day. But how is it possible for babies to have 100 more bones than adults?
Well, baby bones are made entirely of cartilage, which makes them very flexible. The flexibility is very much needed for the babies so they can curl up in their mother’s womb. But as your baby grows, the cartilage will be replaced by actual bone.
Additionally, some of them will fuse together, which leads to a decrease in the number of bones, from 300 to 206.