The development of a child’s feet starts very early on. By the 7th week of pregnancy, the feet are completely formed including the joints and toes. At birth, the average size of a baby’s foot is 7.5 cm. At this stage the bones are very soft and supple as many of the bones are just starting to calcify. The ligaments are loose, the muscles are weak and there is no sign of any arch. The feet will appear flat, largely due to baby fat and a lack of developed arch. The arches do not fully develop until age 5 or 6.