Caesarean babies get less of mother’s gut bacteria

Print edition : October 25, 2019

A recent study of neonatal microbiomes (gut bacteria), the largest ever undertaken, has shown that babies born vaginally have different microbiomes than those delivered by caesarean. Scientists from the Wellcome Sanger Institute, University College, London, the University of Birmingham and their collaborators found that whereas vaginally born babies got most of their gut bacteria from their mother, babies born by caesarean did not. Instead, their gut bacteria were associated more with hospital environments. The study has been published in the latest issue of “Nature”.

The gut microbiome is a complex ecosystem of millions of microbes, and is thought to be important for the development of the immune system. Lack of exposure to the right microbes in early childhood has been implicated in autoimmune diseases such as asthma, allergies and diabetes.

However, the exact role of babies’ microbiomes on their later health and immune system is unclear; in particular, if these differences at birth have any later impact, a release from Wellcome Sanger Institute said. Significantly, the researchers found that most of these differences evened out by the age of one. But larger follow-up studies are needed to determine if the microbiome differences do have any influence, the release added. Experts from the Royal College of Obstetricians and Gynaecologists said that these findings should not deter women from having a caesarean delivery.

The study also revealed that the microbiome of vaginally delivered newborns did not come from the mother’s vaginal bacteria, but from the mother’s gut. This calls into question the controversial practice of swabbing babies born through caesarean with the mother’s vaginal bacteria, the release said.

The researchers studied 1,679 samples of gut bacteria from nearly 600 healthy babies and 175 mothers. Faecal samples were taken from babies aged four, seven and 21 days old, who were born in hospitals in the United Kingdom. In some cases, follow-up was carried out for babies up to one year.

The researchers isolated, grew and sequenced the genomes of over 800 of these potentially pathogenic environmental bacteria, confirming that they were the same as strains causing bloodstream infections in U.K. hospitals.

All women who have a caesarean delivery are now offered antibiotics before delivery. The baby also receives a dose of antibiotics through the placenta. This could also cause some of the microbiome differences seen between the two birth methods.

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