Recent
studies have challenged the century-old notion that the human fetal environment
is sterile and that the neonate's microbiome is acquired during and after
birth. A recent study published in the Journal of Science Translational
Medicine reported the presence of unique commensal placental microbiome from
the Firmicutes, Tenericutes, Proteobacteria, Bacteroidetes, and Fusobacteria
phyla.
Research has
shown that seeding of healthy microbiome at birth is crucial for human health
in later life. Another study published in September issue of American Journal
of Obstetrics and Gynecology does not support the existence of microbiomes
within the healthy fetal milieu, and this concept of ‘sterile womb’ have
implications in the development of practices like ‘vaginal seeding’ after
cesarean births.
The
researchers from Norway and Sweden randomly sampled amniotic fluid from study
cohort of uncomplicated pregnancies at term from 1 of the three sites included
in the Preventing Atopic Dermatitis and Allergies in children (PreventADALL) study. The amniotic fluid from 65 pregnancies was
collected under sterile conditions, ten samples were from women undergoing
elective, planned cesarean section and 14 were from women who had prior rupture
of membranes.
Women with
ruptured membranes have more than 10-fold higher concentration of prokaryotic
DNA (16S rRNA) gene copies/mL. More than 50% samples of amniotic fluid from
ruptured membranes cohort showed bacterial growth in anaerobic cultures, while
all samples from women who had intact membranes were sterile.
The bacteria
identified on culture were vaginal commensals and/ or intrauterine pathogens
including Streptococcus agalactiae, Peptoniphilus harei/ asaccharolyticus,
Lactobacillus reuteri/crispatus/vaginalis, and Prevotella amnii/bivia.
The authors
concluded that in uncomplicated pregnancies, fetal development occurs in a
sterile environment and fetal microbiome is seeded following rupture of
membranes. Understanding the timing of the first microbial colonization in
fetus could help the researchers in a better understanding of the origin of
many diseases.
