A broken fingernail can seem to take forever to grow out if you're an adult. Children and young teens are the ones who get a lucky break -- their nails heal and grow back much faster. Many parents can attest to cutting a squirming child's nails almost every other day. When it comes to nail growth, age and health play an important role.
Nails are made of a protein called keratin, and their growth is affected by several different factors, including age and health. Children's nails grow quickly until puberty when growth slows to 50 percent of its previous rate [source: Robb-Nicholson]. Pregnant women also experience accelerated nail growth -- hormones boost metabolism and increase circulation, which causes nails and hair to grow more quickly. On the other hand, illnesses and certain drugs, such as chemotherapy, can slow nail growth or even cause nails to fall off