Is not the womb sterile?

Babies could come in contact with the first bacteria already in the womb

Is the child already exposed to bacteria in the womb? © Janulla / thinkstock
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Unpopulated: The human microbiome may develop in the womb - not after birth. As a study suggests, the uterus is anything but sterile. Findings of bacterial DNA in amniotic fluid and stool samples from newborns point to this. The baby could contrary to common assumption thus already come in the womb with first beneficial bacteria in contact.

That beneficial bacterial housemates play a crucial role in our health is now well known. But when does this microbiome begin to develop? For a long time, medical experts assumed that the first contact with bacteria takes place in the birth canal. By contrast, the uterus was considered sterile - at least as long as nothing went wrong during pregnancy.

For this reason, it was also believed that babies born by caesarean section may have a disadvantage. After all, they do not come into contact with the valuable vaginal bacteria that would otherwise be the first members of the future microbial community in the body. Meanwhile, this assumption is increasingly questioned: Could it be that the microbiome is already established in the womb?

Settled or not?

"In recent years, bacterial DNA has been found repeatedly in the amniotic fluid and in the first stool of newborns, " said Lisa Stinson of the University of Western Australia at Perth. "Some argued, however, that these findings were due to contamination of the samples analyzed."

To determine definitively whether the fetus is growing up in a sterile environment or not, Stinson and her colleagues have now carried out another study. To do so, they analyzed the amniotic fluid of 50 women who had undergone a planned cesarean section and also examined the chair of newborn children. The special feature: the scientists took very complex measures to avoid contamination by sampling and analysis. display

Influence on the immune system

The result: "Nevertheless, we detected bacterial DNA in almost all samples, " says Stinson. In concrete terms, the researcher and her team detected bacteria in 36 out of 43 usable amniotic fluid samples and microbes were also detected in stool samples of all 50 babies. Interestingly, the feces of the children was individually very different composition. In the amniotic fluid, on the other hand, there were mainly typical skin bacteria such as Propionibacterium acnes and Staphylococcus species.

Further investigations revealed a striking correlation: Depending on the type and amount of bacteria in the amniotic fluid and stool, the local concentration of important modulators of the immune system, such as cytokines or certain, short-chained fatty acids, differed. "This suggests that the fetal microbiome may affect the child's immune system, " states Stinson.

Further studies are needed

As the scientists point out, neither the mothers nor the children showed signs of infection. They therefore assume that the bacteria found are in fact part of a useful or at least intact microbial community. This could decisively influence the baby's early development.

To make sure that the human microbiome is already formed in the womb, further studies are needed in the future. For: So far, Stinson and her colleagues have detected only bacterial DNA. "The next step will be to confirm that the bacteria live in the womb and form a true microbiome, " concludes Stinson. (Frontiers in Microbiology, 2019; doi: 10.3389 / fmicb.2019.01124)

Source: Frontiers

- Daniel Albat