Lanugo is a soft, downy hair that is present on the body of a fetus. It usually begins to grow in the third trimester of pregnancy and disappears shortly after birth. Lanugo is thought to help protect the fetus’s skin from the amniotic fluid.
In some cases, lanugo may persist after birth. This is most commonly seen in premature infants or infants who are born with low birth weight. Persistence of lanugo may also be seen in infants with certain medical conditions, such as hypothyroidism or Down syndrome.
- Insulation: Lanugo helps to keep the fetus warm in the womb by providing a layer of insulation. This is particularly important during the early stages of development when the fetus has not yet developed a sufficient layer of body fat to regulate its temperature.
- Skin protection: Lanugo helps protect the delicate fetal skin from the amniotic fluid in which it is immersed. Without this protective layer, the skin may become too soft and fragile due to constant exposure to the fluid.
- Vernix caseosa formation: Lanugo also plays a role in the formation of vernix caseosa, a thick, waxy substance that coats the fetus’s skin. Vernix caseosa provides additional insulation, protects the skin from the amniotic fluid, and helps to ease the passage through the birth canal.
Lanugo is typically shed before birth, usually around the 33rd to 36th week of gestation, as the fetus develops a more substantial layer of body fat for insulation. The shed lanugo is often swallowed by the fetus and becomes part of the meconium, the infant’s first bowel movement after birth. Some newborns, particularly those born prematurely, may still have some lanugo present on their skin, which will usually disappear within the first few weeks of life.
Lanugo may not be directly associated with the skincare or beauty industry; however, understanding various hair types can significantly improve client management. There are three distinct hair types: lanugo, vellus hairs, and terminal hairs; that each has its own characteristics and effects on the skincare and beauty industry.