This is such an exciting arena of work and advancement. While the arena of the "placental microbiome" has nearly garnished more editorials than original research, their continues to be more original and well controlled research demonstrating a low biomass, low abundance metagenomically identifiable community that is distinguishable from contaminant controls. Irrespective of which side of the "great sterility debate" it is undeniable that in humans and primates, maternal exposures alter the offspring microbiome. The question thus arises, what maintains this as a low biomass, low abundance community? Maternal immunity? Placental immunity? Developing fetal immunity? Efforts which tie maternal microbiome fitness to developing immunity via the placenta, and characterize the underlying molecular intermediates, are crucial.