Babies born through caesarean sections have more than double the risk of early childhood asthma and allergies, a new study claims.
In a study of 700 children, US researchers have found a link between babies born by a caesarean (C-section) and having asthma and allergies at the age of six years.
A caesarean – a surgical procedure to deliver a baby through incisions in the abdomen and uterus – unintentionally stops babies from receiving beneficial microorganisms in their mother’s birth canal.
This in turn hinders the development of a baby’s immune system and can double the risk of the respiratory conditions, the experts say.
A caesarean section, or C-section, interferes with a baby’s ability to obtain beneficial germs from the mother’s microbiome. Pictured, medical staff pull a new born baby from a mother via C-section
WHAT IS THE GUT MADE OF?
Living inside of your gut are 300 to 500 different kinds of bacteria containing nearly 2 million genes.
Paired with other tiny organisms like viruses and fungi, they make what’s known as the microbiota.
Like a fingerprint, each person’s microbiota is unique: The mix of bacteria in your body is different from everyone else’s mix.
It’s determined partly by your mother’s microbiota – the environment that you’re exposed to at birth – and partly from your diet and lifestyle.
The bacteria live throughout your body, but the ones in your gut may have the biggest impact on your well-being.
They line your entire digestive system. Most live in your intestines and colon.
There is evidence it affects everything from your metabolism to your mood to your immune system.
C-section, which is opted for by around one in four pregnant women in the UK, interferes with a baby’s ability to obtain these beneficial or ‘probiotic’ microscopic lifeforms.
The experts’ study has implications for understanding the role of C-section delivery in potentially skewing a child’s microbiota – the trillion-strong community of beneficial microorganisms.
Microbiota is also known as the microbiome – although this latter term includes the collective genomes of the microorganisms in a particular environment, as well as the microorganisms themselves.
Researchers say the microbiome does develop in babies born via C-section, but it may take longer than those who have a natural birth.
‘Every generation of mothers hands over its microbiome to the next, as the baby is coated with beneficial germs while being squeezed through the birth canal, but this doesn’t happen for babies born through C-section,’ said study author Professor Martin Blaser at Rutgers University in New Jersey, US.
‘It takes a while for babies born through C-section to develop a normal microbiome and during that time, while the immune system is also developing, they become more at risk for later developing certain diseases like asthma.
‘This study provides a mechanism for the known link between C-section birth and heightened risk of asthma.’
The researchers analysed the effects of vaginal birth versus C-section during the first year of life for 700 children.
They examined the effects of C-section delivery on the diversity and maturity of gut microbial composition during the first year of life.
To do this, researchers examined children’s faecal samples at the ages of one week, one month and one year.
They then explored whether gut microbial perturbations due to delivery mode were associated with a risk of developing asthma in the first six years of life.
The composition of the microbiome may be substantially affected by cesarean section delivery, researchers say. Pictured, illustration of probiotic bacteria. Probiotic means a microorganisms with beneficial properties. Bacteria is a type of microorganism, as are protozoa and fungi
The researchers found that delivery by C-section was associated with more than a doubled risk of later asthma and allergies by the age of six, as well as significant changes in the composition of the gut microbiota.
However, at one year of age, the risk of asthma was reduced in C-section-born children if their gut microbiota had recovered from its initial disruption and begun to mature normally.
‘Even though a child is born by C-section and has an immense early microbial perturbation, this may not lead to a higher risk of asthma if the microbiome matures sufficiently before age one year,’ said study author Jakob Stokholm at the Copenhagen Prospective Study on Asthma in Childhood.
‘Our study proposes the perspective of restoring a caesarean section-perturbed microbiome and thereby perhaps prevent asthma development in a child, who is otherwise at high risk.’
The findings should not deter women from having the potentially life-saving procedure, which can be performed in an emergency, such as when the baby is in the breech position (with its feet first).
MailOnline has contacted the researchers over whether they controlled for other demographic factors that may have influenced the results.
For example, it’s possible that mothers who opted to undergo C-sections had been conscious of protecting their baby from microscopic bugs, which could have lowered the immune systems of their baby.
The study has been published in Science Translational Medicine.
WHAT ARE THE MEDICAL REASONS FOR A C-SECTION?
There are various reasons why a doctor may recommend that you have a caesarean section instead of giving birth vaginally.
If you had complications in a previous pregnancy or birth, or in your current pregnancy, you may be advised to have what’s called a planned or elective caesarean, or a planned repeat caesarean.
If you were planning to give birth vaginally, but complications during labour or birth mean that you’re advised to give birth by caesarean, you’ll have what’s called an unplanned or emergency caesarean.
Here are some reasons why doctors may opt for a planned or emergency caesarean, rather than a vaginal birth:
- You’ve already had at least one caesarean section.
- Your baby is in a bottom-down, or breech, position.
- Your baby is in a sideways (transverse) position, or keeps changing its position (unstable lie).
- You have a low-lying placenta (placenta praevia).
- You have a medical condition, such as heart disease or diabetes.
- You have lost a baby in the past, either before or during labour.
- You’re expecting twins or more.
- Your baby is not growing as well as it should be in your womb.
- You have severe pre-eclampsia or eclampsia, making it dangerous to delay the birth.