Source: Pubmed central.
Akinbi, H. T., Narendran, V., Pass, A. K., Markart, P., & Hoath, S. B. (2004). Host defense proteins in vernix caseosa and amniotic fluid. American Journal of Obstetrics and Gynecology, 191(6), 2090–2096.
In this study, researchers analyzed samples of amniotic fluid and vernix caseosa (vernix) from healthy, term gestations to determine the immune properties of these substances. Participants were pregnant women admitted for elective cesarean section after 37 weeks gestation with no prior labor and no signs of chorioamnionitis (intrauterine infection). Women with a history of prenatal fever or premature rupture of membranes, or who received steroids prenatally or antibiotics while giving birth were excluded, as were women whose babies passed meconium in utero, had congenital malformations, or required prolonged resuscitation after birth. Amniotic fluid was obtained by amniocentesis to determine fetal lung maturity prior to elective birth. Vernix was gently scraped from the newborn's skin with a sterile implement immediately following birth. The researchers obtained 10 samples of amniotic fluid and 25 samples of vernix.
Tests (Western analysis and immunochemistry) revealed that lysozyme, lactoferrin, human neutrophil peptides 1–3, and secretory leukocyte protease inhibitor were present in the amniotic fluid samples and in organized granules embedded in the vernix samples. These immune substances were tested using antimicrobial growth inhibition assays and found to be effective in inhibiting the growth of common perinatal pathogens, including group B. Streptococcus, K. pneumoniae, L. monocytogenes, C. albicans, and E. coli.
The authors point out that the innate immune proteins found in vernix and amniotic fluid are similar to those found in breast milk. As the baby prepares for extrauterine life, pulmonary surfactant (a substance produced by the maturing fetal lungs) increases in the amniotic fluid, resulting in the detachment of vernix from the skin. The vernix mixes with the amniotic fluid and is swallowed by the growing fetus. Given the antimicrobial properties of this mixture, the authors conclude that there is “considerable functional and structural synergism between the prenatal biology of vernix caseosa and the postnatal biology of breast milk” (p. 2095). They also suggest that better understanding of these innate host defenses may prove useful in preventing and treating intrauterine infection.
Significance for Normal Birth
Routine artificial rupture of membranes increases the likelihood of intrauterine infection because it eliminates the physical barrier (the amniotic sac) between the baby and the mother's vaginal flora. This study suggests an additional mechanism for the prevention of infection when the membranes remain intact: A baby bathed in amniotic fluid benefits from antimicrobial proteins that are found in the fluid and in vernix caseosa.
The results of this study also call into question the routine use of some newborn procedures. Early bathing of the baby removes vernix, which contains antimicrobial proteins that are active against group B. streptococcus and E. coli. Delaying the bath and keeping the newborn together with his or her mother until breastfeeding is established may prevent some cases of devastating infections caused by these bacteria. The fact that preterm babies tend to have more vernix than babies born at or after 40 weeks might mean that healthy, stable preterm babies derive even greater benefit from staying with their mothers during the immediate newborn period.
Finally, this study illustrates how the normal physiology of pregnancy and fetal development is part of a continuum that extends beyond birth to the newborn period. The immunologic similarities between amniotic fluid, vernix, and breast milk provide further evidence that successful initiation of breastfeeding is a critical part of the process of normal birth.