Is there a placental microbiota? A critical review and re-analysis of published placental microbiota datasets.
Level 4 - case-series / case-control
Pooled re-analysis of cross-sectional sequencing datasets (by design analogy, non-clinical CEBM)
PubMed 36934229 · doi:10.1186/s12866-023-02764-6
What was done
Fifteen publicly available 16S rRNA gene datasets of human placental samples were uniformly re-analyzed using the DADA2 pipeline to evaluate evidence for a placental microbiota. Analyses evaluated the impact of environmental background DNA removal on term cesarean delivery samples and conducted a six-study sub-analysis of the 16S rRNA gene V4 hypervariable region comparing placental tissue profiles against technical controls and delivery modes.
What was found
The abstract reports no numerical values. Amplicon Sequence Variants (ASVs) identified as Lactobacillus were initially prevalent across studies but disappeared after removing likely contaminant DNA from term cesarean delivery samples. In the six-study sub-analysis, placental samples shared principal bacterial ASVs with technical controls and clustered primarily by study origin and mode of delivery rather than demonstrating a consistent resident microbial community.
Why it matters
This uniform re-analysis clarifies that bacterial DNA detected in typical term human placentas is attributable to environmental contamination and delivery mode rather than a resident placental microbiome.
Limits
The abstract does not report the total number of human subjects included across the datasets. The analysis is limited to retrospective computational re-analysis of existing 16S rRNA sequencing data without prospective sample collection or live-bacterial culture validation.
Cited by
- supports Human infants are born sterile and acquire their gut microbiome postnatally from immediate surroundings and parents.