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Background. Branched Chain Fatty Acids (BCFA) are rare in mammalian lipids but are known to be synthesized in the sebaceous gland. They are richest in vernix caseosa, the substance that covers the fetus in late gestation. During pregnancy, the fetus swallows amniotic fluid and with it sloughed vernix particles. We recently reported the presence of BCFA in meconium, the first pass of the neonate. Since vernix and meconium are the input and output, respectively, of the GI tract, we hypothesized that the BCFA profile of the two would be related in some systematic way. Methods. Vernix was skimmed off newborns in the delivery room and meconium was collected into diapers and saved for analysis. Samples were processed by a modified Bligh & Dyer extraction, and FAME were analyzed by GC and GC/MS. The BCFA profiles for vernix and meconium was compared for individual neonates and on average. Results. Vernix BCFA contain iso‐BCFA, anteiso‐BCFA, dimethyl BCFA and middle‐chain monomethyl BCFA and range from 12 to 26 carbons. In contrast, meconium BCFA are mainly iso‐BCFA and range from 16 to 26 carbons. Major differences in profiles were found from infant to infant. Conclusions. BCFA are a normal component of the term newborn gut throughout its entire length. BCFA with <16 carbons and with branching other than iso disappear in the sterile fetal gut in late gestation. The mechanism is unknown. Funding: NIH GM071534.
Ran‐Ressler et al. (Sat,) studied this question.