Vernix caseosa

[2] Vernix has a highly variable makeup but is primarily composed of sebum, cells that have sloughed off the fetus's skin and shed lanugo hair.

[1] The lipids include ceramides, cholesterol, fatty acids, triglycerides, waxes and sterol esters, squalene, and phospholipids;[1] multiple detailed analyses of the polar components have been done.

[1] As opposed to stratum corneum, the vernix corneocytes lack desmosomal attachment and the lipid layer is more disordered.

[1][11][12] Vernix appears in all full term infants but with widely varying body-coverage, while premature and post-mature births generally do not display any.

[6][2][13] It is theorized (and observed) to serve several purposes:[1][2][11] Electrical isolation of the fetus is also thought to occur due to vernix caseosa (this could affect accurate fECG measurement of fetal heartbeat).

[2] Vernix is thought to be unique to human fetal development; in 2018, vernix-like material was reportedly obtained from pups of the California sea lion.