alt=Baby held in a gloved hand, with creamy substance smeared all over|thumb|300x300px|Newborn baby immediately after birth, covered in vernix
Vernix caseosa, or simply vernix, is the waxy white substance found coating the skin of newborn human babies. It is produced by dedicated cells and is thought to have some protective roles during fetal development and for a few hours after birth.
Etymology
In Latin, vernix means varnish and caseosa means cheesy. The term was first published in 1846 in the Dunglison Dictionary of Medical Sciences. Vernix, in itself, is also believed to aid in the formation of stratum corneum. By early third trimester, the process is complete.
Soon enough, part of the vernix is emulsified by increasing concentrations of pulmonary surfactants and desiccates, only to be consumed by the fetus; a corresponding increase in amniotic fluid turbidity is noticed. Chemically, it is water (80%), lipids (10%) and proteins (10%). The total fatty acid profile in vernix (either as part of lipids or as fatty acids) contains a variety of less common fatty acids, such as omega-7 polyunsaturated fatty acids or non-methylene-interrupted omega-3 fatty acids.
The protein composition is relatively understudied.
The cells are polygonal or ovoid in shape, malleable, and lack nuclei; typical thickness is 1-2 μm.
Physical properties
Vernix is a white viscous cream-like substance in appearance.
Functions
Vernix appears in all full-term infants, with widely varying body coverage. Premature and post-mature births generally do not display any.
It is theorized (and observed) to serve several purposes:
Medical uses
Vernix is used as a reliable site-of-record for measuring cocaine exposure in pregnant women. Using vernix for diagnosing uterine rupture and amniotic fluid embolism has been proposed. Mass spectrometry of the material showed it to be fundamentally the same as human vernix, in both BCFA (branch-chain fatty acids) and squalene content. The presence of vernix throughout the infant gastro-intestinal tract, as well as in the meconium (first excretion), in both human and sea lion neonates, argues that the function of vernix may not be as an external skin protection, as often described in the literature, but as a preparation of the newborn GI tract against water-borne bacteria. As such, vernix caseosa, not present in any terrestrial mammal, including other primates, is one of several arguments for a possible semi-aquatic past of our ancestors.
Additional images
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Vernix feet.jpg|Vernix on a newborn's legs and feet.
Newborn minutes after delivery.jpg|Traces of vernix on a full term newborn.
Postpartum baby3.jpg|Closeup of baby's face right after birth, skin covered in vernix and some blood.
</gallery>