Lanugo

Lanugo

Lanugo is a type of fine, downy hair that covers the body of a human fetus. This soft, thin hair begins to appear around the fifth month of gestation and plays a crucial role in the development and protection of the fetus. Lanugo is typically shed by the fetus by the ninth month of gestation, shortly before birth, although some newborns may still have remnants of lanugo for a short period after birth.

Overview

Lanugo is the first type of hair to be produced by the follicles of a developing fetus. It is usually unpigmented or very lightly pigmented. The primary purpose of lanugo is to aid in the adherence of the vernix caseosa, a waxy protective coating on the skin of the fetus. Together, the lanugo and vernix caseosa help to regulate the fetus's temperature and protect the skin from amniotic fluid, potentially preventing chapping or hardening.

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Illustration showing lanugo on a human fetus.

Development and Shedding

Lanugo begins to develop around the fifth month of gestation as part of the fetus's normal growth process. It covers the entire body except for the palms of the hands, soles of the feet, and the lips. Starting around the seventh or eighth month of gestation, the lanugo is gradually shed and absorbed by the fetus, a process that is usually complete by the ninth month. However, it is not uncommon for some newborns, especially those born prematurely, to have visible lanugo, which they typically shed within the first few weeks of life.

Function

The functions of lanugo include:

• Protection from amniotic fluid: Lanugo, together with vernix caseosa, protects the fetus’s skin from being softened or eroded by prolonged exposure to amniotic fluid.
• Temperature regulation: Lanugo helps in maintaining an appropriate body temperature for the fetus.

Postnatal Considerations

While most full-term newborns will have shed their lanugo before birth, those born prematurely may still have noticeable lanugo. This hair is harmless and will naturally fall out within the first few weeks of life. The presence of lanugo in newborns does not require any medical treatment, as it is a normal part of fetal development.

Clinical Significance

Persistent lanugo in older children or adults may be indicative of certain health conditions, including eating disorders like anorexia nervosa, where it is thought to be a physiological adaptation to the body's attempt to conserve heat during periods of significant weight loss and malnutrition.

External Links

• National Center for Biotechnology Information - Skin Development
• Medscape - Neonatal Skin Overview

References

• Pediatric Dermatology: A Quick Reference Guide by the American Academy of Pediatrics
• Fetal and Neonatal Physiology by Richard A. Polin and Steven H. Abman

Lanugo Resources
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