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Our exposure to bacteria begins before we’re born according to new research led by The University of Western Australia. The study, published in Frontiers in Microbiology , used rigorous contamination controls to confirm that exposure to bacteria begins in the womb.

Lead author Dr Lisa Stinson, from UWA’s Faculty of Health and Medical Sciences, said the researchers collected amniotic fluid samples from 50 healthy women undergoing planned caesarean deliveries, and found that nearly all contained bacterial DNA. The researchers subsequently found all 50 newborns had bacteria in their first bowel movement.

“Over the last decade, numerous studies have detected bacterial DNA in amniotic fluid and first-pass meconium (baby’s first poo), challenging the long-held assumption that the womb is sterile,” Dr Stinson said.

“However, some argue that the results are false positives – contaminants in the reagents used in DNA analysis.”

The researchers said it was important to conclusively determine whether a healthy womb contained bacteria because the ‘fetal microbiome’ was likely to have a significant impact on the developing immune system, gut and brain.

To settle the issue, the research team took strict measures to eliminate bacterial contamination when analysing amniotic fluid and meconium samples.

For example, they purified the reagents used to detect bacterial DNA in the samples, by adding an enzyme which digests DNA remnants from bio-manufacturing.

“Despite these measures, we still found bacterial DNA in almost all samples,” Dr Stinson said.

“Interestingly, the meconium microbiome varied hugely between individual newborns. The amniotic fluid microbiome for the most part contained typical skin bacteria, such as Propionibacterium acnes and Staphylococcus species.”

None of the women who took part in the study nor their babies had any sign of infection. In fact, the fetal microbiome may prove to be a beneficial regulator of early development.

“We found that levels of important immune modulators in meconium and inflammatory mediators in amniotic fluid varied according to the amount and species of bacterial DNA present,” Dr Stinson said.

“This suggests that the fetal microbiome has the potential to influence the developing fetal immune system.”

Dr Stinson said there was one small caveat – technically, the DNA in these samples could have come from bacteria that were already dead in the womb.

“Here we’ve proven that bacterial DNA is present in the womb, but the next step will be to show whether these are alive and constitute a true microbiome,” concludes Stinson.

Media references

Lisa Stinson (UWA Faculty of Health and Medical Science)                                  0468 676 189

Simone Hewett (UWA Media & PR Adviser)                                                        08 6488 7975