Final answer:
Lanugo is a type of fine, colorless hair that primarily covers fetuses and is shed close to birth. Newborns might have traces of lanugo, which usually disappears within the first few weeks after birth.
Step-by-step explanation:
Lanugo is a type of hair found primarily on fetuses. This fine, colorless hair starts to grow on the fetus's face and eventually covers most of the body. It serves as a protective layer for the developing baby and is usually shed close to the time of birth, during approximately weeks 17-20. The presence of lanugo is one manifestation of a fetus's development inside the womb.
After birth, newborns may still have traces of lanugo, but it typically disappears within the first few weeks of life as part of the adaptation to the environment outside the womb. The lanugo is replaced by vellus hairs, which are fine and short hairs that cover the body and serve as the first form of hair in postnatal growth.