The great English biologist, Desmond Morris, once wrote (The Naked Ape -1967) that of 193 different species of primate, only one is born naked: Humans. Unbeknown to him at the time, we are covered in hair throughout much of our time in utero.

During the second trimester, or at approximately 3-4 months, babies grow moustaches. It all starts on the upper lip, where a super fine hair forms and gradually over the next month or so, spreads to cover its entire body.

This super fine hair is called Lanugo. Lanugo derives from the Latin meaning for “wooly down” and acts as an anchor for vernix (full name; vernix caseosa). Together they help to protect a baby’s delicate skin from the amniotic fluid, helps thermoregulation, prevents water loss, provides innate immunity and finally helps lubricate the baby’s way through the birth canal. Without lanugo, the vernix would have no anchor and all these functions would become compromised.

Lanugo is often shed before birth, however its presence does not indicate prematurity. As the baby sheds the lanugo, it enters the amniotic fluid (click here for more on the wonders of amniotic fluid), where it is then swallowed and joins other products to form meconium, the first sticky bowel movement of a newborn.

After we shed our lanugo, it is replaced by hair covering the same surfaces. This fine, non-pigmented hair of infancy is called vellus, from Latin and means “fleece”, it is finer and more difficult to see. The more visible hair that continues into adulthood is called terminal hair.