Also called vernix caseosa. A cheesy, white substance that covers a baby's skin at birth. The vernix is secreted by the sebaceous glands around the 20th week to protect the baby's skin from the amniotic fluid. Without the vernix, the baby would have very wrinkled skin from constant exposure to the watery amniotic fluid. The amount of vernix present decreases toward the end of gestation. Remaining vernix is washed off after birth. The loss of vernix may cause the skin to peel during the first postnatal week.