Long-term chronic disease risk for people born by C-section worth examining

WATCH ABOVE: Birth by caesarean section, also known as C-section, is on the rise for a number of reasons. Dr. Samir Gupta examines the possible risk of long-term chronic diseases for people born by caesarean section, compared to those born naturally. 

An analysis published in the British Medical Journal by Jan Blustein and Jianmeng Liu on June 10 has emphasized the possible risk of long-term chronic diseases imparted to people born by caesarean section, compared to those born naturally (vaginal birth).

This has brought the issue of our rising caesarean section rates back to the forefront, and is worth examining.

Firstly, we are seeing more and more caesareans, for several possible reasons.

In the last 20 years, rates have increased dramatically in middle income countries like Brazil, Mexico, China (around 50 per cent of births), as well as the US (around 33 per cent of births), and Canada (27 per cent of births in 2013, compared to 19 per cent in 1997).

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That compares to the 15 per cent rate which we would expect to see for medical reasons alone, as per recommendations made by the World Health Organization.

There are lots of possible reasons for the increase. One is the advent and increased use of electronic fetal heart rate monitors.

When these monitors are used, more caesareans are performed, but there are no important long-term improvements in the baby’s well-being.

In many cases, we do not fully know how to interpret fetal heart rate tracings, and experts have suggested that doctors may often overreact to monitoring abnormalities.

Similarly, doctors tend to default to a caesarean in women who have had one before, even though this is not always necessary.

Some studies suggest that in places like the U.S., this may be driven by a fear of litigation.

In other parts of the world, like China, we’re seeing caesarean rates driven by patients. Twenty per cent of Chinese women actually ask for caesarean because of a (false) perception that it’s safer.

In light of all this, this analysis is particularly interesting. Authors put together the evidence from studies seen over the last decade or so that have compared the long term health of people born through normal vaginal delivery to those born through caesarean section.

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There are several “meta-analyses” (analyses of results from multiple individual studies), which consistently show certain trends.

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In summary, they suggest about a 3.6 per cent higher risk of obesity (based on 9 studies), a 1.6 per cent higher risk of asthma (based on 23 studies), and a 3.4 in ten thousand higher risk of type 1 diabetes (based on 20 studies), in people born through caesarean.

The caveat is that all of these data are observational – what are called either cohort or case-control studies.

The challenge with this type of information is that there could be a “confounder” that we are missing.

For example, pregnant women who have asthma that are active during pregnancy are at a higher risk of a pregnancy-related complication called “pre-eclampsia,” which can put the fetus at risk as well.

Accordingly, mothers with active asthma are more likely to have caesareans on this basis. However, because asthma is partly hereditary, the children of these mothers are also more likely to have asthma.

So if we just looked at the numbers, it may seem as though children born by caesarean have a higher rate of asthma, but actually it is not due to the caesarean, but rather to a confounder – the fact that the child’s mother has asthma too.

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These studies measure as many of these confounders as they can, and adjust for these in their analyses, but all data are not always available, and there may well be confounders that we are not aware of. However, there are some interesting theories as to how a caesarean birth may lead to some of these chronic conditions.

In normal delivery, the fetus is exposed to the natural bacteria in the birth canal, and studies show that those are the bacteria that end up colonizing the infant’s intestines.

Research also suggests that the bacteria in an infant’s intestine play an important role in how they absorb nutrients (which could later affect their weight), and how their immune system takes shape (which could conceivably influence an auto-immune disease like type 1 diabetes).

There’s also a theory that the physical stress of vaginal delivery causes certain genes to become activated in the baby (through what is called “epigenetics”), which can then result in several downstream developmental changes.

Top 5 maternal advantages of a vaginal delivery over a caesarean

When it’s safe to proceed with a vaginal delivery, studies suggest several advantages for the mother, compared to a caesarean:

5. Less blood loss

4. Less infections – such as urinary tract infections and infections of the lining of the uterus which can be seen after caesareans

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3. No surgical complications – such as anaesthetic complications, and blood clots which can occur after caesareans

2. Shorter hospital stay

1. A more rapid overall recovery

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