Microbiome of C-Sections

For years caesarean sections have provided a safe way to deliver new babies, and in many cases, they save both their and their mother’s lives. However, elective c-sections are on the rise and studies are now trying to work out what effect they have on a child’s health long-term.

Caesarean sections (or c-sections) are the removal of babies after surgically cutting the mother’s abdomen and womb. There are usually three reasons to have a c-section: elective (i.e. the mother has chosen to have a c-section for usually non-medical reasons), planned (i.e. the c-section is planned as there may be risk to the child or mother which is known early), or emergency (i.e. there were complications during labour and the baby needed to be delivered quickly). Whilst in the UK it is still less common to opt for an elective c-section, the number of c-section delivered babies across the Globe nearly doubled between 2000 and 2015, from 12% of all births (16 million) to 21% (29.7 million).  The World Health Organisation (WHO) suggest that a c-section rate of more than 15% is excessive for any given country. This is troubling for countries such as the Dominican Republic which has a c-section rate of 58.1%. WHO state that women who need c-sections should still have access to them but “many others undergo the procedure unnecessarily“.pregnant.png

Why is it important to not deliver babies through c-section unnecessarily? To answer that, we need to know what a microbiome is. “The microbiome comprises all of the genetic material within a microbiota (i.e. the entire collection of microorganisms in a specific [part], such as the human gut)“. It is the collection of bacteria, viruses and fungi which live within each of us. Everyone is individual and thought to be more complicated than our genome! The microbiome is linked to affecting the development of our immunity, defence against pathogens, synthesis of vitamins and fat storage, and influences some human behaviour amongst other things, thus making it an essential part of the body without which we would not function well. So what does this have to do with c-section babies?goodmicrobes.png

For years, studies have demonstrated potential links between c-section births and future conditions such as asthma, obesity, diabetes and allergies to name a few. Research published in Nature this Sept’19, has highlighted higher levels of bad bacteria found in hospitals are present in c-section babies’ microbiomes. This study was the largest yet conducted on newborn microbiomes (~600 births in the UK), and provides strong evidence that children born vaginally have a different microbiome to their c-section peers. Not only is the microbiome different, but those babies born via c-section lacked gut bacteria which are present in healthy children and adults, but did have some harmful microbes which are commonly found in hospitals. The impact of the lack of certain bacteria is yet to be studied, but the presence of harmful microbes is obviously of concern. The children’s faeces were sampled at 4, 7 and 21 days after birth to gain the microbiome information. The differences were so stark, that researchers were able to confidently predict the method of delivery from a sample.

When born vaginally, children are exposed to their mother’s gut microbes (probably at the moment of birth, not the beautiful picture you imagined…), potentially giving them protection from certain conditions much like breast milk does in delivering helpful antibodies. It is hypothesised that initial exposure to these gut bacteria at birth could be a “defining moment” for the immune system, deciding how sensitive to be and which bacteria to defend against. The children were all reassessed months later, finding their microbiotas were more similar; 60% of the c-section children had few to no potentially harmful bacteria in their gut at 9 months old. This bacteria has known antibiotic resistance and is commonly found in hospitals. Previous research has suggested that the presence of such bacteria could influence the host’s immune system.c-section

All of this research is part of a much larger project called the Baby Biome Study. Researchers hope to recruit 40,000 participants across the UK, with an aim to understand how microorganisms (i.e. the bacteria, virus and fungi in our microbiomes) interact with our immune system, and how clinical, social and behavioural factors during pregnancy and early life can influence health and disease later in life. The findings could prove to be very interesting. C-sections have saved so many lives, and will continue to do so. However, our microbiomes are very complicated, and such studies could help determine if non-essential c-sections (elected) are unnecessarily detrimental to a child’s future health, especially in a world with increasing antibiotic resistance.

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