Caesarean delivery has low impact on childhood allergic outcomes

Anastasia Tsirtsakis

17/03/2020 11:11:04 AM

A study conducted by the Murdoch Children’s Research Institute found no obvious impact of caesarean delivery on allergic outcomes.

Person with eczema
One in three Australian children are diagnosed with eczema.

New research published in Archives of Disease in Childhood has found no association between caesarean delivery and eczema or lung function, and a small link between delivery method and asthma.
The research team, headed by the Murdoch Children’s Research Institute’s (MCRI) Professor Melissa Wake and Dr Rachel Peters, used parent-reported asthma and eczema data drawn from the HealthNuts study (3135 participants) and the Longitudinal Study of Australian Children (LSAC) of 3654 participants aged 6–7 years, as well as lung function data from the Child Health CheckPoint study of 1502 participants aged 11–12 years.
Group leader of Growing Up in Australia’s Child Health CheckPoint study, pediatrician Professor Melissa Wake said previous data from the 1990s suggesting a link between caesarean delivery and childhood allergic diseases warranted further investigation given that a ‘normal delivery, if it’s possible’ has numerous benefits for babies.
‘It prepares their lungs for breathing air and it also exposes the baby to the mother’s healthy normal vaginal flora bacteria,’ Professor Wake told newsGP.  
‘That early exposure to the mother’s bacteria helps set the baby’s microbiome and therefore their own immune health.’
Almost one in five people in Australia has an allergy, making it one of the allergy capitals of the world.
The numbers have sharply risen since 1990, particularly among children: one in three children has eczema and one in four will be diagnosed with asthma.
This increase has occurred in parallel with rapidly rising rates of caesarean section. Of the 309,000 births in Australia in 2015, 33% of babies were born by caesarean section – a figure that far exceeds the World Health Organization’s recommendation of between 10–15% for optimal maternal and neonatal outcomes.  
‘The global caesarean rate is higher than 20%, and North America, East Asia and the Pacific regions, including Australia, all now have caesarean rates around 30%,’ Dr Peters said.
‘At the same time, rates of asthma and eczema in children aged 6–7 years globally are 12% and 8%, respectively, with higher prevalence reported in Australia [20% and 17%].’
Professor Wake said the results are ‘very reassuring’ and particularly important, as they consider the prevalence among local children.
‘We look at this as being quite a definitive study in a way because we were able to look across all three cohorts, all of which had very strong information and come up with essentially the same findings,’ she said.
Dr Peters, an epidemiologist within the population allergy research group at the MCRI, said the results can give parents confidence that if they want or need a caesarean birth their child is unlikely to be at higher risk of having eczema and poor lung function than children delivered vaginally.
‘And only a possible small risk of developing asthma,’ she added.
The association between caesarean delivery and asthma was found in the HealthNuts study but not in LSAC, making the interpretation of the finding a little less clear.
Dr Peters and her colleagues believe the study could hold deeper answers, however. They are currently looking back through the participants to assess whether the risk of allergic outcomes may differ depending on whether the mother has had an emergency or elective caesarian.
‘With an elective caesarian the infant is less likely to be exposed to the mother's microbiome. But in the case of an emergency caesarian and labor has started, then the infant may be exposed to the mother’s microbiome,’ she said.
‘So we may possibly see a difference in risk there. But we don’t have an answer to that yet.’
While there is currently no direct answer as to why allergy rates are higher in Australia than overseas, Dr Peters says that one of the mechanisms is the ‘hygiene hypothesis’.
‘It proposes that an absence of exposure to microbes or infections in infancy skews the development of the immune system towards an allergic phenotype,’ Dr Peters told newsGP.
There are several environmental factors associated with microbial exposure aside from mode of delivery, such as early exposure to pets in the household, rural or farming lifestyles, or attending childcare.
Food allergy is another area of mounting concern in Australia, where one in 10 infants is diagnosed with a food allergy by 12 months of age.
There has been substantial research in recent years to suggest infants should be exposed to a variety of foods, particularly the allergenic variety, in the first year of life, Dr Peters said.
She suggests GPs look at the Australian Infant Feeding Guidelines available through the Australasian Society of Clinical Immunology and Allergy (ASCIA) to encourage parents about best practice.
‘They recommend that solids should be introduced at around six months of age and not before four months when an infant is developmentally ready, and that allergenic foods such as peanut and egg should be introduced in the first year of life,’ Dr Peters said.
‘That would be a really great message for GPs to get across.’
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