What is the proper term for fetal hair?

The proper term for fetal hair is "lanugo." This fine, soft hair covers the body of a fetus in the womb and typically appears around the 16th week of gestation. It plays a role in protecting the delicate skin of the fetus and may help to regulate body temperature and facilitate development during fetal life. Lanugo is usually shed before birth or shortly thereafter, being replaced by vellus hair, which is the fine, soft hair found on most of the human body after infancy. Recognizing lanugo as a specific term associated with fetal development is key in understanding hair growth stages in human biology.