Babies born by caesarean section have a higher risk of infection by disease-causing bacteria

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Billions of bacteria, viruses and fungi coexist in the body of any human being , healthy or sick. Not only in the digestive tract - the famous intestinal flora - but also in the skin, eyes, mouth or lungs. Knowing what is the normal balance of these colonies of microbes that populate our organs and knowing how to repair it when it breaks represents one of the great promises of modern medicine. But, for now, discoveries in this field raise many more questions than scientists can answer.

Some researchers look for these responses in the early stages of life, studying newborns. Nature magazine published a study yesterday that demonstrates that the type of birth conditions the intestinal flora of neonates. "Babies are sterile while in the womb, but as soon as they are born, their immune system receives a large number of bacteria," explains Nigel Field, a researcher at University College London. «We believe that this may be the moment that regulates everything that will come next; That is why we designed this study, to understand how babies are colonized by microbes in those first moments of life ».

Previous research had suggested that bacteria were transmitted from mother to child in the birth canal. However, this study - the largest so far on the neonatal microbiota - reveals that newborns have very few bacteria of vaginal origin and that most come from the maternal intestine . Possibly received during the same delivery. "We believe that most bacteria can come from the perineum," says Peter Brocklehurst, a professor at the University of Birmingham, "so it may not be a coincidence that we are born so close to our mothers' anus."

In addition, according to research data, about 83% of babies born by caesarean section carried pathogens that could cause disease, compared with 49% of those born by vaginal delivery. Results that could support the gynecologists' own indications of the need to reduce the number of caesarean sections performed worldwide.

The authors clarify that their results should not dissuade women from having a cesarean delivery , if circumstances advise. They stress that the exact role of intestinal bacteria in the baby is still unclear and that there is no evidence that these differences have a lasting effect on health. In fact, the results seem to reflect that the divergence tends to disappear after the first year of life. "There is still much to investigate," says Brocklehurst, "we cannot say that a procedure is better or worse because we still do not know the long-term consequences."

According to the authors, the results do call into question a controversial practice, vaginal or micropartum seeding. This is a method that applies to some children born by caesarean section to those who rub with a sample of maternal vaginal fluids, hoping to stimulate the creation of the microbiota. A practice against which the British Medical Journal had already pronounced for exposing babies to bacteria without a clear benefit. "If planting were important, we would have seen more bacteria of vaginal origin and that was not the case," says Field.

On the other hand in babies born by caesarean section there is a greater amount of bacteria associated with the hospital environment. In this regard, researchers remind that all women who undergo a C-section are given antibiotics before delivery to help prevent the onset of postoperative infections, which means that the baby also receives a dose through the placenta. This seems to make them more prone to resistance to antimicrobial drugs. "But, for now, we have not been able to determine the extent to which the use of antibiotics has a bearing on the type of delivery," says Brocklehurst.

Understanding the microbiome

The intestinal microbiome is a complex ecosystem in which hundreds of bacteria are believed to coexist. Microbes that help us digest food, develop our organs or prevent disease. It is suspected that they may even influence the immune system and our behavior. The absence of some of these bacteria in early childhood has been linked to some autoimmune diseases such as asthma, allergies and diabetes.

But determining exactly the role of the microbiome in health is a difficult task, since it is complex to establish whether imbalances in these microorganisms are the cause or effect of diseases. To overcome this obstacle, researchers have analyzed more than 1,679 fecal samples of intestinal bacteria in 600 healthy babies and 175 mothers, which were collected by the latter and sent by letter to the researchers.

Thus, the authors were able to isolate, cultivate and sequence the genome of more than 800 potentially pathogenic bacteria. "Babies born by caesarean section had more bacteria than are normally acquired in hospitals, the so-called opportunistic pathogens ," says Field. "Although these bacteria generally do not cause disease while they are in the intestine, they can be created if they enter the wrong place or if the immune system fails."

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