What is known as baby fetal hair that typically falls off a few weeks after birth?

Lanugo refers to the fine, soft hair that covers a developing fetus and is typically present in the later stages of pregnancy. This hair is usually produced around the fourth or fifth month of gestation and serves to protect the delicate skin of the fetus and help maintain its body temperature. After birth, lanugo often sheds within the first few weeks of life, as the baby develops and their skin matures.

Vellus hair, while also fine and soft, is the hair that covers most of the human body after lanugo is gone, and it is not specific to fetal development. Terminal hair is coarser and longer, emerging in response to hormonal changes during puberty, and keratinized cells do not refer to hair but rather the cells that have undergone a process of keratinization, leading to the formation of the outer layer of the skin and hair. Therefore, lanugo is the only term specifically related to the fine hair that is typical during fetal development and falls off shortly after birth.