Lanugo: What Is It, Purpose, Causes & Treatment (original) (raw)

What does lanugo do?

Lanugo is an essential part of fetal development. It plays a critical role in protecting fetal skin and keeping it warm in the uterus.

Lanugo helps vernix (the waxy, cheese-like substance that covers the fetus) stick to the skin. Vernix helps protect a fetus’s body from amniotic fluid inside the uterus. Amniotic fluid could damage its delicate skin without lanugo and vernix. When vernix is held in place by lanugo, it helps insulate the body and protect the skin. Lanugo also helps the fetus stay warm and regulates its temperature until it develops enough body fat to serve this purpose.

Lanugo also helps the fetus grow. This occurs because the lanugo hair sends vibrations to fetal sensory receptors when it moves. These receptors stimulate fetal growth. When lanugo falls off, the stimulation stops, and fetal growth slows down. Experts are not entirely sure how this happens, but continue to study this and other hormonal effects of lanugo.

When does lanugo fall off?

Most fetuses shed lanugo shortly before birth. About 30% of all full-term babies are born with some lanugo. If your baby is born premature (before 37 weeks), they have a greater chance of having lanugo. It may take several weeks to go away, but lanugo will fall off on its own.

Lanugo typically falls off in the last eight weeks of pregnancy. Once it’s shed from the skin, it mixes in with amniotic fluid. Because the fetus swallows amniotic fluid in the uterus, lanugo becomes part its first food. Your baby will pass the tiny hairs in their first poop at birth, called meconium.

After the fetus sheds lanugo, it develops vellus hair, a fine, peach-fuzz-like hair. The vellus hair continues to help regulate temperature until adult hair (terminal hair) grows in.

Why do people with eating disorders get lanugo?

Lanugo is one of the side effects of anorexia nervosa, bulimia nervosa and other eating disorders in adults. It can indicate poor nutrition and malnourishment. Healthcare providers believe lanugo grows when a person doesn’t have enough body fat to keep them warm. In response, their body grows lanugo to help insulate the body.