Lanugo is very thin, soft, usually unpigmented hair that is sometimes found on the body of a fetus or newborn.

As the lanugo is shed from the skin, it is normal for the hair to be consumed by the developing fetus, since it drinks from the amniotic fluid and urinates into its environment.

The presence of lanugo on newborns is not necessarily a sign of premature birth, as it is also seen on infants born at thirty-nine weeks of gestation (full term).

It provides lubrication for birth and contributes to thermoregulation, prevention of water loss, and innate immunity.

[6] In the absence of fat, lanugo grows to serve as a replacement insulator, and thus can be observed in malnourished patients, including those with eating disorders.