What parts of the human body are the same size at birth as in adulthood?

The ear, with the only three bones (hammer, anvil, stirrup) in the body that remain the same size from birth to death.

http://www.eternalkeys.ca/DoesGodExist4.html

According to the text Ocular Pathology by D. J. Apple and M. F. Rabb (Mosby, 1985) the diameter of a newborn's eyeball is about 18 mm; it increases rapidly during the first year of life, but after this, growth is very slow. The reasons behind eyeball growth are not precisely known. This was discussed in a great book by Richard J. Goss called The physiology of growth (Academic Press, 1978, pp. 191-199).

http://www.madsci.org/posts/archives/jan2000/949009575.An.r.html