Vernix Caseosa: What You Should Know

Vernix caseosa is a natural, protective, and nourishing substance that coats the skin of all newborn babies. Learn more about it today!

Written and verified by the dermatologist Maria del Carmen Hernandez.

Last update: 11 April, 2023

Not everyone knows what vernix caseosa is. However, it plays an essential role in the development of the fetus and the newborn. It’s a greasy, whitish substance that covers the skin surface of babies. In this article, we’ll tell you everything you should know about it.

What is vernix caseosa?

Vernix caseosa is a physiological, viscous biofilm. It’s produced by the desquamated skin of the fetus itself and the sebaceous glands that cover it in the third trimester of pregnancy. It’s composed of 80.5% water and 10.3% lipids and the rest is made up of proteins. The lipids are produced by the sebaceous glands (sebum) and the stratum corneum (ceramides).

The most superficial layer of the fetal skin is still immature and its desquamation is mixed with the sebum produced by the sebaceous glands.

When does the vernix caseosa develop?

As the layers of the fetal skin form, it undergoes keratinization and desquamation. As the development of the epidermis evolves, buds form at the root of the hair follicles that will become the sebaceous glands. Therefore, the combination of the superficial layer of the epidermis and sebum is what constitutes the fetal vernix caseosa, which reaches its maximum production in the third trimester of pregnancy.

From the 36th week of gestation, the levels of this substance begin to decrease, until it usually disappears completely in the 41st week.

Vernix caseosa functions

The main physiological function of vernix caseosa in the baby’s development is to help the fetus adapt outside the uterus. Namely:

1. The formation of the viscera inside the uterus: It’s in direct contact with the amniotic fluid, where many of its components are detached and mixed, which is a supply for the fetus.
2. Temperature regulation: The hydrophobic layer developed by the vernix contributes to thermoregulation, according to a review in the Journal of Obstetrics and Gynaecology Research. Keeping it on the baby’s skin for as long as possible can naturally stabilize body temperature.
3. Skin formation: Vernix acts as a biofilm that hydrates and moisturizes, creating healthy, smooth skin. In addition, its high vitamin E content can provide protection from the sun’s ultraviolet rays.
4. Healing of burns and wounds: The high concentration of enzymes, peptides, lipids, and water contributes to the healing of wounds and burns.
5. Antimicrobial defenses: Certain components, such as enzymes, immunopeptides, and lipids in vernix caseosa act to recognize and/or suppress skin flora as it develops.

It provides multiple maturation functions linked to skin development in utero and adaptation after birth. Therefore, it reflects that there are intimate fetal and maternal interactions.

When should vernix caseosa be cleaned from the baby’s body?

Vernix caseosa, in addition to keeping the newborn’s skin hydrated and moisturized, prevents it from cracking or drying out excessively. It even contributes to the development of the skin’s acid mantle and to completing its maturation. For this reason, it’s advisable not to bathe the newborn immediately, but rather to wait 3 to 4 days so as not to remove this protective substance. In fact, the World Health Organization (WHO) recommends postponing the baby’s first bath for at least one day.

The most important thing is for the newborn to adapt to the external environment outside the womb and to stabilize all vital signs. In addition, much of this substance will be absorbed naturally by the skin or will be shed on its own.

The importance of vernix caseosa during the moment of delivery

The sebaceous ointment is essential in vaginal delivery due to its ability to act as a lubricant. That is, it can contribute to the delivery and expulsion of the baby and allow for better displacement. In addition, it tends to accumulate to a greater extent in the region of the back, scalp, and folds of the extremities. Therefore, it can reduce friction as the newborn passes through the birth canal during birth.

Vernix caseosa: Final considerations

Vernix caseosa is a natural, protective, and nourishing substance that coats the skin of all newborn babies. It also has wound-healing and antibacterial properties for the baby and helps at the time of delivery. It’s important to keep the sebaceous ointment on the newborn’s skin for as long as possible.