Secretion
The sebum in vernix is produced in utero by the sebaceous glands around the 20th week of gestation. Vernix appears primarily in full term infants, while premature and postmature births generally lack any. Postdates desquamation (flakey skin in babies born >42 weeks) is thought to be due to loss of vernix.
Read more about this topic: Vernix Caseosa