Vernix has a highly variable makeup but is primarily composed of sebum
, cells that have sloughed off the fetus's skin and shed lanugo
12% of the dry weight of vernix is branched
-chain fatty acid
. Vernix of term infants has more squalene
and a higher wax ester
to sterol ester
ratio than preterm infants.
Vernix is theorized to serve several purposes, including moisturizing the infant's skin, and facilitating passage through the birth canal
. It serves to conserve heat and protect the delicate newborn skin from environmental stress. Vernix is also thought to have an antibacterial effect;
though there is little to support a chemical role of vernix in protecting the infant from infection, it may form a physical barrier to the passage of bacteria.