Which Body Parts Do Not Grow From Birth?
All body parts of a normal, healthy human increase in size after birth through maturity, according to the Encyclopedia Britannica. A common myth states that the eye is at its full size at birth, but in actuality, the eye grows for some time after. KidsHealth points out that refractive changes that occur during childhood are an easily identified indicator of this growth.
A study published in the U.S. Library of Medicine tracked the growth of eyes in nearly 2,000 healthy Indian children from birth to maturity. In the study, the size of the males' eyes tracked through the infancy stage increased between 13 and 23 percent, while the size of the females' eyes increased between 17 and 30 percent during the same period. The rate of eye growth slows after infancy for most growth metrics except for medial intercanthal distances. The relatively small changes may contribute to the perpetuation of the myth that human eyes do not grow after birth.
Other post birth growth changes are more dramatic. The head makes up approximately 25 percent of the body length of a newborn, while its limbs account for approximately 37 percent of the length, according to the Biology Reference webpage. These ratios shift so that by maturity the head accounts for only around 12 percent of body length, while the limbs are 50 percent of body length.