Population Health Research Net

Hospitalisation for bronchiolitis in infants is more common after elective caesarean delivery_⁽¹⁾

Overview:

Researchers at the world renowned Telethon Institute for Child Health Research (TICHR) in Perth, Western Australia have been at the forefront of studies into acute respiratory infections (ARI) in young children for a number of years.

A previous study by the TICHR team found an increased risk of hospital admissions for ARI in children under 2 years of age, delivered by elective caesarean. (see case study # 4)

With elective caesarean rates increasing worldwide and other research showing an increased risk of asthma in children born by caesarean (c-section) it was important to progress the TICHR team's initial research further.

A new study aimed at examining associations between the number of hospital admissions for bronchiolitis and pneumonia and elective caesarean delivery was carried out and in October 2011 its results were published in the online edition of the international journal Archives of Disease in Childhood.

What data were used to perform the study?

The study analysed linked birth data and hospitalisation records of 212,068 babies over a ten year period in Western Australia.

Data were extracted using the Western Australian Data Linkage System (WADLS), a record linkage system that brings together data from numerous population-based administrative health datasets.

A population cohort of non-Aboriginal singleton live births of 37-42 weeks gestation between 1996 and 2005 was identified.

The study was approved by the Princess Margaret Hospital for Children Ethics Committee. Access to data from WADLS was approved by the Confidentiality of Health Information Committee and the WA Data Linkage Branch

What were the main results of the study?

In conducting their study the research team found evidence of an independent association between elective caesarean delivery and repeated hospitalisations for bronchiolitis in infants, a finding that to their knowledge has not been previously reported.

The study found that a higher proportion of infants delivered by elective caesarean than by any other delivery methods were admitted to hospital at least once for bronchiolitis between 1996 and 2005. The effect, after adjusting for a range of maternal factors and pregnancy complications, was an 11 per cent increase in multiple hospital admissions.

What did the authors conclude from their results?

Having completed the research study the authors have now highlighted the need for continued research into the suspected role of various natural chemicals (cytokines) that are produced by mothers during labour in priming a newborn's immune system.

According to lead author Dr Hannah Moore "we compared elective caesareans with other modes of delivery because with elective c-sections we could be confident that labour had not begun and therefore the baby would not have been exposed to those chemicals that are released during the labour process,"

"It is increasingly plausible that delivery without labour could impair a newborn's immune system and may also explain the known link between c-sections and an increased risk of asthma."

In Summary:

This latest research which highlights an association between elective caesarean delivery and hospitalisation frequency for bronchiolitis, adds to the body of evidence surrounding the different immunological environment of elective c-section delivery and the relationship between early viral illness and subsequent asthma.

The study authors believe that physicians and expectant parents need to be made aware of this additional risk of elective c-sections and associated infant morbidity to aid in deciding the most appropriate mode of delivery.

The research team believe that qualitative studies are now needed to understand women's and physicians' views regarding elective c-section delivery.

They also believe that laboratory studies should be undertaken to test the hypothesis that elective c-section delivery results in altered development of antiviral immunity in infants.

Journal reference:
1 Moore, H.C., de Klerk, N., Holt. P., Richmond, P.C., Lehmann, D.
Hospitalisation for bronchiolitis in infants is more common after elective caesarean delivery
doi: 10.1136/archdischild-2011-300607
Arch Dis Child published online October 28, 2011

This study was funded by the National Health and Medical Research Council Project Grant #572590

For more information on this study click :
http://adc.bmj.com/content/early/2011/10/28/archdischild-2011-300607.full