We’ve had the best look yet at the microbes that make themselves at home in our bodies in the months following birth. Many of these organisms are mystery species, and the study suggests that being born by C-section may have less of a long-lasting effect on the microbiome than previously thought.
Our microbiome – the microbes that live in our gut and elsewhere on our body – plays a crucial role in our health. However, we don’t really know how the body’s microbial community becomes established once we’re born.
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To find out, Nicola Segata of the University of Trento, Italy, and colleagues recruited 25 mothers and their babies. They sampled bacteria from each mother’s gut, via faecal samples, as well as from their mouth, vagina, breast milk and skin. Genetic analysis enabled them to compare these bacteria with those present in the babies’ mouth and faeces during their first four months of life.
The researchers found a very high diversity of microbes in the infant gut within 24 hours of birth. This diversity plummeted over the following week, then gradually recovered over the next four months. This suggests many different microbes initially move into the body, but only a few of these become established.
At first, babies contain bacteria from many different sites from across their mother’s body, but microbes from their mother’s skin and vagina disappear soon after. “This doesn’t mean they’re not important. The organisms that are there in the first place are probably help shape the baby’s immune systems,” says Segata.
Delivery method
Gut bacteria from the mother eventually dominate an infant’s gut microbiome, and the team found that breast milk was probably an important source of these microbes. In fact, breastfeeding had a greater effect on a baby’s microbiome than the microbes they picked up from their mother’s birth canal.
The impact of vaginal verses Caesarean birth on the infant microbiome is a hot research topic, with some people giving babies a swab of vaginal fluid after they’re been born by Caesarean section in the hope that it gives them a good set of gut bacteria.
Interestingly, the researchers found that microbial transmission from the mother is a continuous process, with some types of bacteria appearing in the babies weeks and months after birth. Bacteria from the mother were also far more likely to persist in their baby compared to bacteria from other sources in the wider environment.
One of the most intriguing findings was that some of the bacteria passed from mother to infant belong to unknown species that have not been described before. “These species are potentially very important for our health and one would have expected that they had been discovered already,” says Segata.
Cell Host & Microbe
Read more: What lives inside you: A guide to your microbiome
