Vernix, also known as vernix caseosa, is a creamy white coating that develops on the unborn baby's skin at around 20 weeks of pregnancy. It is believed to act as a moisturiser, and protects the baby's skin while it is in the womb.
Towards the end of pregnancy, the vernix covering the baby begins to lessen. Therefore, most full term babies are born with little or no trace of the substance, although it is common for premature babies to have a coating of vernix.
Vernix is primarily composed of sebum, which is secreted from the foetus's glands. As well as protecting the skin, vernix is believed to hold antibacterial properties, which may help to guard against infection.
For this reason, many advocate leaving the vernix on the skin of a newborn, rather than wiping it away. Additionally, the moisturising properties of vernix can also help to prevent drying and cracking of a newborn's delicate skin.
However, some parents do prefer to remove vernix, and this can be done by gently wiping the substance off the newborn baby's skin, or by gently massaging it in.
Any remaining vernix will eventually be absorbed by the baby's skin, or will slowly flake away.