Is a foetus developing in a sterile environment?

@article{Wassenaar2014IsAF,
  title={Is a foetus developing in a sterile environment?},
  author={Trudy M. Wassenaar and Pinaki Panigrahi},
  journal={Letters in Applied Microbiology},
  year={2014},
  volume={59}
}
Novel findings in microbiology question the long‐standing paradigm that a healthy pregnancy implies a sterile uterus. It now seems that the placenta is frequently colonized with bacteria, and a placental microbiome has been identified. Recent literature findings are summarized here, and an attempt is made to separate pathological bacterial presence from a naturally occurring microbiome. 
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Is there evidence for bacterial transfer via the placenta and any role in the colonization of the infant gut? – a systematic review
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Current data are limited and provide no conclusive evidence that there is a normal placental microbiome which has any role in colonization of infant gut.
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References

SHOWING 1-10 OF 62 REFERENCES
Mom Knows Best: The Universality of Maternal Microbial Transmission
TLDR
Evidence for microbial maternal transmission is increasingly widespread across animals, and collective knowledge compels a paradigm shift—one in which maternal transmission of microbes advances from a taxonomically specialized phenomenon to a universal one in animals.
Comment on “The placenta harbors a unique microbiome”
  • H. Kliman
  • Biology, Medicine
    Science Translational Medicine
  • 2014
Microbiota found in the placenta may actually be bacteria or bacterial fragments in maternal blood.
Author response to comment on “The placenta harbors a unique microbiome”
  • K. Aagaard
  • Medicine
    Science Translational Medicine
  • 2014
TLDR
Placental samples contain very small volumes of blood, and blood-borne bacteria are not likely to be detected in microbiome analysis, so these samples are unlikely to be used for microbiome analysis.
The Placenta Harbors a Unique Microbiome
TLDR
A unique placental microbiome niche was characterized, composed of nonpathogenic commensal microbiota from the Firmicutes, Tenericute, Proteobacteria, Bacteroidetes, and Fusobacteria phyla, which was consistently different from those reported in other parts of the body, including the skin and urogenital tract.
Meconium microbiota types dominated by lactic acid or enteric bacteria are differentially associated with maternal eczema and respiratory problems in infants
Culture‐dependent methods have shown that meconium, the newborn's first intestinal discharge, is not sterile, but the diversity of bacteria present in this material needs to be further characterized
Transmission of Diverse Oral Bacteria to Murine Placenta: Evidence for the Oral Microbiome as a Potential Source of Intrauterine Infection
TLDR
This study provides the first insight into the diversity of oral bacteria associated with intrauterine infection, with a higher prevalence in the placenta than in the pooled saliva or subgingival plaque samples, indicating that the placental translocation was species specific.
Meconium Microbiome Analysis Identifies Bacteria Correlated with Premature Birth
TLDR
This work provides the first evidence to support the hypothesis that the fetal intestinal microbiome derived from swallowed amniotic fluid may be involved in the inflammatory response that leads to premature birth.
Dendritic cells and the intestinal bacterial flora: a role for localized mucosal immune responses.
TLDR
Mechanisms of interaction between intestinal bacteria and DCs and the role of localized gastrointestinal immune responses are discussed.
Vaginal and oral microbes, host genotype and preterm birth.
Microbial Prevalence, Diversity and Abundance in Amniotic Fluid During Preterm Labor: A Molecular and Culture-Based Investigation
TLDR
The amniotic cavity of women in preterm labor harbors DNA from a greater diversity of microbes than previously suspected, including as-yet uncultivated, previously-uncharacterized taxa.
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5
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