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Evidence for contamination as the origin for bacteria found in human placenta rather than a microbiota

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Paper Summary

Paperzilla title
Is the Placenta a Sterile Sanctuary? Contamination Likely Explains Bacterial Presence

The study found no substantial evidence for a resident placental microbiome in term births. Bacterial presence in the placenta was linked to contamination during delivery, especially in vaginal births, while chorionic villi showed lower bacterial presence than other sampled areas. This challenges previous findings suggesting a consistent placental microbial community.

Explain Like I'm Five

Scientists found that the tiny living things in a baby's placenta probably just snuck in during birth, like dirt getting on your new shoes, instead of living there all along.

Possible Conflicts of Interest

This work was supported by a PRIDE grant from the hospital-university department "Risks in Pregnancy" and by Paris Descartes university. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No other conflicts were identified.

Identified Limitations

Small sample size for metagenomics and potential bias from sample processing time
The sample size for the metagenomics analysis is quite small (n=7), limiting the generalizability of the findings. Additionally, the higher diversity found in external samples could be due to longer time intervals between membrane rupture and sample processing, introducing bias and making it difficult to isolate the effect of the different delivery modes.
Limited investigation of factors influencing bacterial presence in vaginal delivery samples
Although bacterial DNA was found in fetal membranes and umbilical cords collected after vaginal delivery, the study doesn't fully explore the factors contributing to this finding, such as the timing of membrane rupture or specific procedures during delivery.
Lack of alternative explanations beyond contamination
The study's focus is on challenging the existence of a placental microbiome, which is a valid scientific endeavor. However, it could be strengthened by proposing alternative explanations for findings reported in previous studies, beyond contamination, or by suggesting further research to explore potential low-biomass microbial communities in the placenta.

Rating Explanation

This study uses a robust methodology, comparing various placental removal methods, sample areas, and analysis techniques (culture, qPCR, metagenomics). It also carefully considers and controls for contamination. The findings challenge the existence of a consistent placental microbiota and offer an alternative explanation for bacterial presence, significantly contributing to the ongoing debate in this field. Despite some limitations, like the small sample size for metagenomics and limited investigation of contributing factors in vaginal delivery samples, the strengths of the study's methodology justify the rating.

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Topic Hierarchy

Domain: Health Sciences
Field: Medicine
Subfield: Urology

File Information

Original Title: Evidence for contamination as the origin for bacteria found in human placenta rather than a microbiota
Uploaded: July 14, 2025 at 10:53 AM
Privacy: Public