Biology of the vernix caseosa: A review.

The vernix caseosa is a complex membranous structure comprising 80% water, 10% protein, and 10% lipids including barrier lipids such as ceramides, free fatty acids, phospholipids and cholesterol, synthesized partly by fetal sebaceous glands during the last trimester of pregnancy in an antero-posterior and dorsoventral manner. Because of its lipid content, vernix is hydrophobic and protects the skin from excessive water exposure during the development of the stratum corneum. The vernix caseosa has various functions during fetal transition from an intrauterine to an extrauterine environment, including lubrication of the birth canal during parturition, barrier function to prevent water loss, temperature regulation, for innate immunity and for intestinal development. This review discusses the evidence supporting the prenatal and postnatal functions of vernix caseosa, along with its structure, composition, and physical and biological characteristics. Understanding the biology of the vernix may facilitate improved care of preterm infants immediately post-partum.