Sept. 26, 2014

By Medical Discovery News

While we know for sure that the bacteria living in and on us are key to our own well-being, more evidence suggests that we acquire our microbiomes before we’re even born. While a baby does acquire bacterial flora from its mother as it moves through the birth canal, scientists now think that our symbiotic, life-long relationships with bacteria begin in utero long before birth. They found bacteria living in the placenta, an organ previously thought to be sterile. They also discovered a baby’s bacteria to be similar to the bacterial flora of the mother’s mouth, making oral hygiene during pregnancy extra important.

An experiment in 2008 by Spanish scientists indicated that bacteria are acquired in some way before birth. They inoculated pregnant mice with labeled bacteria, which were then found in the meconium, the first bowel movement after birth. This was true even when the babies had been delivered by C-section. So scientists knew then that bacteria are acquired before birth and even without the birth canal, changing what we thought we knew about the womb.

Since then, scientists at Baylor College of Medicine have been studying the inside of the womb and birth canal in both humans and animals. They discovered that the vaginal microbiome changed during pregnancy, but it did not resemble that of newborns. So where did they get their bacteria from?

Baylor scientists then examined placentas from 320 women immediately after birth. Using DNA sequencing, they identified the individual types of bacteria each placenta contained. Comparing them to bacteria growing in and on the mothers, they found that the types of bacteria living in the mothers’ mouths most closely resembled those in their own placentas. Interestingly, the bacteria in the placenta consisted of high proportions of bacteria responsible for synthesizing vitamins and other nutrients, which probably benefits a developing fetus and newborn. So a fetus is first exposed to bacteria from the placenta, then at birth additional bacteria are introduced, and then again when babies are exposed bacteria on their parent’s skin, in breast milk, and in their environment.

Other studies have shown the influence of the microbiome on a mother and her baby. In one experiment, monkeys who ate a high-fat diet while pregnant and lactating produced babies with different proportions of bacteria in their guts than those of monkeys fed a normal diet. The short- and long-term consequences of abnormal maternal and infant microbiomes are not yet known, but it’s speculated that these changes could influence the metabolism of the infant and the development of metabolic disorders.

Science is increasingly aware of the role and importance the microbiome has in various parts of the body and the part it plays in human health and disease.

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