- The downy hair on the body of the fetus and newborn baby. The lanugal hair (or lanugo) is the first hair to be produced by the fetal hair follicles. It is very fine, soft and usually is unpigmented. The lanugal hair is prenatal hair. It appears at about 5 months of gestation and begins to be shed at 7 and 8 months of gestation. The postnatal hair that succeeds the lanugal hair is conventionally divided into vellus and terminal hair. The vellus resembles the lanugal hair in that it is short, soft and usually unpigmented. The terminal hair is longer, coarser and usually pigmented. There are intermediate types of hair. Any given follicle can change the type of hair it is making. "Lanugo" is the Latin word for down, like the fine small hairs of plants.
Medical dictionary. 2011.