What is the Vernix Caseosa?

Vernix caseosa is a white substance that covers the skin of a fetus. This natural coating helps prevent the chapping and wrinkling of an unborn baby's skin. As babies spend months in amniotic fluid, this substance performs an extremely important purpose. In fact, vernix caseosa may even help protect a baby’s skin from infection, as the proteins within it have antibiotic properties. This substance may also help clean a baby’s skin while he’s still in his mother’s womb and help to make it easier for a baby to move through its mother’s birth canal.

The term vernix caseosa is Latin. Vernix means varnish, which is a reasonable description of this protective substance. Caseosa means cheesy, which is also pretty accurate, as the substance is white and cheesy or waxy looking. This substance comes from a baby’s sebaceous glands and consists of oil and skin cells that have been rubbed off.

Typically, babies are born with vernix caseosa still in place, though babies born after a full-term pregnancy are likely to have only part of this coating left over. Premature babies, on the other hand, are often completely covered with it. The reason for this difference is a chemical that stimulates amniotic fluid production. After a baby's lungs develop fully, which typically happens close to full-term birth, they produce a chemical that causes the body to make more amniotic fluid; this appears to cause the vernix caseosa layer to deteriorate somewhat. Since premature babies are often born before the lungs develop fully, this deterioration may not occur before birth.

Without this substance, a baby’s skin might looked not only chapped, but also very wrinkled. It might resemble the way a person’s skin looks after he’s soaked in a bath for an exceedingly long time. This protective coating, however, allows a baby’s skin to be smooth and soft at birth, despite that fact that he has spent months in fluid.

Often, newborn babies are shown as completely clean in television childbirth scenes. Usually, the opposite is true, and real newborns have blood, other fluids, and vernix caseosa on their bodies when they are fresh from the womb. New parents may only see this coating briefly, however, as it is usually wiped off soon after birth. Sometimes, however, parents may choose to massage it into their baby’s skin, hoping that their newborn babies will benefit from this natural moisturizer, even after birth.