One area of particular interest is the role which delivery mode plays in the development of the infant/neonate microbiome and what potential implications this may have long term.
[1] One notable study from 2010 illustrated an abundance of Lactobacillus and other typical vaginal genera in stool samples of infants born via vaginal delivery and an abundance of Staphylococcus and Corynebacterium, commonly found on the skin surfaces, in stool samples of infants born via cesarean section.
[6] The evidence suggests that applying microbes from the mother's vaginal canal to the baby after cesarean section may aid in the partial restoration of the infant's natural gut microbiome with an increased likelihood of pathogenic infection to the child via vertical transmission.
It is known that pregnancy results in thickening of the vaginal mucosa and an increase in cervical secretions which in turn leads to smooth muscle cell hypertrophy and relaxation of the connective tissue.
In addition, vaginal epithelium also exhibits hypertrophy which subsequently leads to crowding of the epithelial cells which themselves are rich in glycogen.
[18] In the event that a C-section is done before labour starts or before a woman's water breaks, the infant will not come into contact with maternal vaginal fluid or bacteria.
[7] However, the study authors acknowledged that the long-term consequences of vaginal seeding remain unclear due to limited data.
[23] Infants delivered by C-section are at a lower danger of exchange of some potentially harmful microbes and infections from the birth canal.
Although it remains unknown, vaginal seeding procedures may take these harmful microorganisms, including undetected sexually transmitted infections (STIs) and unintentionally transfer them to the infant.
[24] An editorial written in the British Medical Journal is advising practitioners and parents to not perform vaginal seeding as there is not enough evidence that it is beneficial for infants and could potentially put babies' health at risk.
[25] The American College of Obstetricians and Gynecologists (ACOG) also does not encourage or recommend vaginal seeding due to lack of evidence.
[26] Currently, the establishment of the infant microbiome including what influences are associated with optimal versus dysbiotic outcomes remains as a key component of health research.
In context of the bacterial baptism hypothesis, this is essential, as merely reporting a genre (such as Lactobacillus) would fail to provide insight for the assessment of vertical transmission.
Additionally, maternal alterations in the intestinal microbiome during pregnancy may also play a role in the microbial colonization of vaginally delivered infants.
[27] Given the potential maternal fecal contamination that is prone to occur during vaginal delivery, it is important to consider how alterations in the intestinal microbiome during pregnancy may influence microbial colonization of the infant.