mother playing with a baby with a full head of hair

What is lanugo?

Lanugo is the name for the soft, downy, unpigmented hair that covers Baby’s body beginning in about the fifth month of pregnancy. He will eventually lose all of this pseudo-hair before, or shortly after delivery.

Why does Baby grow lanugo?

In early gestation, Baby doesn’t have enough fat to regulate his own body temperature. As a result, lanugo will begin to grow as a light coating over most of his body to help keep him warm.

When does lanugo fall off?

Lanugo generally sloughs off deeper into pregnancy as Baby gains more of an ability to control his body temperature, with a more highly functioning nervous system, and increased accumulation of fat beneath his super-soft skin. Most babies lose their lanugo in the eighth or ninth month of pregnancy, though some can be born with remnants of the fine coating still on their body. However, nearly all lanugo will be shed by three or four months after birth.

And a disgusting fun fact: babies eat the lanugo that they shed while in the womb, and it builds up within them to form the substance that makes up their first poop, known as meconium.

What’s next for Baby’s hair?

After Baby sheds and eats his lanugo, he will develop vellus hair on the same areas that the lanugo coated previously. The vellus hair will continue to help Baby regulate temperature as he transitions into the outside world until his beautiful adult (terminal) hair grows in.


Reviewed by Dr. Jamie Lo
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Sources
  • N.J. Randall, K Bond, J Macaulay, Philip J Steer. “Measuring fetal and maternal temperature differentials: a probe for clinical use during labor. Department of Obstetrics and Gynaecology, Charing Cross and Westminster Medical School, West London Hospital, UK.” Journal of Biomedical Engineering. 13(6):481-5. DOI: 10.1016/0141-5425(91)90094-N. Web. Dec-91.
  • Mayo Clinic Staff. “Second trimester pregnancy: What to expect.” Mayo Clinic. Mayo Clinic, 5/15/2014. Web.

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