Vernix caseosa

Vernix caseosa, also known as vernix or birthing custard, is the waxy white substance found coating the skin of newborn human babies.[1] It is produced by dedicated cells and is thought to have some protective roles during fetal development and for a few hours after birth.

Newborn baby immediately after birth, covered in vernix

Etymology

In Latin, vernix means varnish and caseosa means cheesy. The term was first published in 1846 in the Dunglison Dictionary of Medical Sciences.[1]

In-utero development

Vernix is produced during a distinct phase of the epidermal development.[2] Around the 21st week of gestation, periderm cells are being shed and replaced with stratum corneum; these shedding mix with secretions of sebum by the sebaceous glands to form vernix, which gradually covers the body in an anteroposterior and dorsoventral pattern.[1][2][3] Vernix, in itself, is also believed to aid in the formation of stratum corneum.[4] By early third trimester, the process is complete.[5]

Soon enough, part of the vernix is emulsified by increasing concentrations of pulmonary surfactants and desiccates, only to be consumed by the fetus; a corresponding increase in amniotic fluid turbidity is noticed.[2]

Characteristics

Composition

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.[6] Chemically, it is water (80%), lipids (10%) and proteins (10%).[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.[7] The protein composition is relatively understudied.[1] Vernix of term infants has more squalene and a higher wax ester to sterol ester ratio than preterm infants.[6]

Morphology

Vernix is composed of mobile corneocytes embedded in an amorphous lipid matrix.[1] Precise biological mechanisms leading to its formation are poorly understood.[8]

The cells are polygonal or ovoid in shape, malleable, and lack nuclei; typical thickness is 1-2 µm.[1] Nuclear ghosts are frequently observed and Acid Phosphatase Activity is nonuniform.[1] Keratin filaments build a scaffold like structure which form a water-storage area.[1] As opposed to stratum corneum, the vernix corneocytes lack desmosomal attachment and the lipid layer is more disordered.[9]

Physical properties

Vernix is a white viscous cream-like substance in appearance.[1]

The water is not uniformly distributed throughout, but rather exclusively present in the sponge-like corneocytes; despite its high water content, vernix is non-polar (due to lipids) and more vapor-permeable than stratum corneum.[1][10][11]

Functions

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][12]

It is theorized (and observed) to serve several purposes:[1][2][10]

  • Electrical isolation of the fetus (this affects accurate fECG measurement of fetal heartbeat).[13]
  • Waterproofing the skin, whilst in gestation.
  • Lubricating the infant's skin, and facilitating easy passage through the birth canal.
  • Preventing infections — primarily as a mechanical barrier and secondarily via the presence of lysozyme, lactoferrin and antimicrobial components in peptide layer.
  • Moisturizing the stratum corneum whilst in gestation (and controlled drying in post-partum phase).
  • Thermoregulation in post-partum phase — evidence is mixed.
  • Quick healing of epidermal wounds.
  • Development of gut, after intra-uterine consumption.

Medical uses

Vernix is used as a reliable site-of-record for measuring cocaine exposure in pregnant women.[2][14] Using vernix for diagnosing uterine rupture and amniotic fluid embolism has been proposed.[2]

Disorders

Granuloma and peritonitis of vernix have been observed in Caesarean sections.[2] High volumes of vernix cause Neonatal Aspiration Syndrome.[2]

Other species

Vernix is thought to be unique to human fetal development; in 2018, vernix-like material was reportedly obtained from pups of Zalophus californianus.[15]

Additional images
  • Vernix on a newborn's legs and feet.
  • Traces of vernix caseosa on a full term newborn.
  • Closeup of baby's face right after birth, skin covered in vernix and some blood.

References
  1. Nishijima K, Yoneda M, Hirai T, Takakuwa K, Enomoto T (November 2019). "Biology of the vernix caseosa: A review". The Journal of Obstetrics and Gynaecology Research. 45 (11): 2145–2149. doi:10.1111/jog.14103. PMID 31507021.
  2. Singh G, Archana G (2008). "Unraveling the mystery of vernix caseosa". Indian Journal of Dermatology. 53 (2): 54–60. doi:10.4103/0019-5154.41645. PMC 2763724. PMID 19881987.
  3. Moore AL, Marshall CD, Nauta A, Lorenz HP, Longaker MT (2019-01-01). "Chapter 5 - Scarless Wound Healing: From Experimental Target to Clinical Reality". In Atala A, Lanza R, Mikos AG, Nerem R (eds.). Principles of Regenerative Medicine (Third ed.). Boston: Academic Press. pp. 65–92. doi:10.1016/B978-0-12-809880-6.00005-9. ISBN 978-0-12-809880-6. S2CID 81194374.
  4. Hoath SB, Shah KN (2017-01-01). "49 - Physiologic Development of the Skin". In Polin RA, Abman SH, Rowitch DH, Benitz WE (eds.). Fetal and Neonatal Physiology (Fifth ed.). Elsevier. pp. 498–514.e4. doi:10.1016/B978-0-323-35214-7.00049-4. ISBN 978-0-323-35214-7.
  5. Karperien M, Roelen BA, Poelmann RE, Gittenberger-de Groot AC, Hierck BP, DeRuiter MC, Meijer D, Gibbs S (2015-01-01). "Chapter 3 - Tissue Formation during Embryogenesis". In Blitterswijk CA, De Boer J (eds.). Tissue Engineering (Second ed.). Oxford: Academic Press. pp. 67–109. doi:10.1016/B978-0-12-420145-3.00003-1. ISBN 978-0-12-420145-3.
  6. Schachner LA, Hansen RC (2003). Pediatric dermatology. St. Louis: Mosby. pp. 206–7. ISBN 978-0-323-02611-6.
  7. Harazim E, Vrkoslav V, Buděšínský M, Harazim P, Svoboda M, Plavka R, et al. (November 2018). "O-acylceramides in vernix caseosa". Journal of Lipid Research. 59 (11): 2164–2173. doi:10.1194/jlr.M088864. PMC 6210899. PMID 30254076.
  8. Hoath SB, Narendran V, Visscher MO (2011). "Vernix Caseosa and Innate Immunity". Innate Immune System of Skin and Oral Mucosa. John Wiley & Sons, Ltd. pp. 145–169. doi:10.1002/9781118025338.ch8. ISBN 978-1-118-02533-8.
  9. Rissmann R, Groenink HW, Weerheim AM, Hoath SB, Ponec M, Bouwstra JA (August 2006). "New insights into ultrastructure, lipid composition and organization of vernix caseosa". The Journal of Investigative Dermatology. 126 (8): 1823–33. doi:10.1038/sj.jid.5700305. PMID 16628195.
  10. Hoath, Steven (2003). Neonatal skin : structure and function (2. ed., rev. and expanded. ed.). New York [u.a.]: Dekker. pp. 193–208. ISBN 0-8247-0887-3.
  11. Visscher M, Narendran V (April 2014). "The Ontogeny of Skin". Advances in Wound Care. 3 (4): 291–303. doi:10.1089/wound.2013.0467. PMC 3985523. PMID 24761361.
  12. Sidbury, Robert (2018), "Newborn Skin Development", Avery's Diseases of the Newborn, Elsevier, pp. 1468–1474.e1, doi:10.1016/B978-0-323-40139-5.00103-0, ISBN 978-0-323-40139-5, retrieved 2021-01-04
  13. Chiera M, Cerritelli F, Casini A, Barsotti N, Boschiero D, Cavigioli F, et al. (2020). "Heart Rate Variability in the Perinatal Period: A Critical and Conceptual Review". Frontiers in Neuroscience. 14: 561186. doi:10.3389/fnins.2020.561186. PMC 7544983. PMID 33071738.
  14. Moore, C.; Dempsey, D.; Deitermann, D.; Lewis, D.; Leikin, J. (October 1996). "Fetal cocaine exposure: analysis of vernix caseosa". Journal of Analytical Toxicology. 20 (6): 509–511. doi:10.1093/jat/20.6.509. ISSN 0146-4760. PMID 8889690.
  15. Wang DH, Ran-Ressler R, St Leger J, Nilson E, Palmer L, Collins R, Brenna JT (May 2018). "Sea Lions Develop Human-like Vernix Caseosa Delivering Branched Fats and Squalene to the GI Tract". Scientific Reports. 8 (1): 7478. Bibcode:2018NatSR...8.7478W. doi:10.1038/s41598-018-25871-1. PMC 5945841. PMID 29748625.
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