C-sections Linked To Small Increase in Childhood Asthma

Dr Mairead Black MBChB, MRCOG, MSc Research Fellow, Wellcome Trust Clinical Lecturer, Obstetrics and Gynaecology School of Medicine and Dentistry, Division of Applied Health Sciences University of Aberdeen Aberdeen Maternity Hospital, Cornhill Road Aberdeen AB25 2ZD

Dr. Mairead Black

MedicalResearch.com Interview with:
Dr Mairead Black MBChB, MRCOG, MSc

Research Fellow, Wellcome Trust
Clinical Lecturer, Obstetrics and Gynaecology
School of Medicine and Dentistry, Division of Applied Health Sciences
University of Aberdeen
Aberdeen Maternity Hospital, Cornhill Road
Aberdeen AB25 2ZD 

Medical Research: What is the background for this study?
Dr. Black: The current thinking is, if a baby is exposed to labour, then it is also exposed to ‘good bacteria’ that mothers pass on during the birth, and they are also exposed to a degree of natural stress at the time of birth that might make them more resistant to developing future illnesses.

The World Health Organisation formerly recommended that no more than 15 percent of deliveries should be C-sections. However rates in some countries have soared – China and Brazil have rates in excess of 50%, whilst in the UK the figure is 26% with almost half of these being planned in advance.

The main purpose of this study was to explore whether health outcomes in children up to very early adulthood differ according to how they are delivered and whether avoiding labour entirely, i.e. via a planned C-section, could put children at a disadvantage compared to those delivered vaginally or by emergency C-section, where most will have been exposed to labour. The study analysed data from over 300,000 births between 1993 and 2007 across Scotland, using routinely collected data from seven linked databases.

Medical Research: What are the main findings?

Dr. Black: The results show that asthma involving a hospital admission was slightly more likely to occur in those delivered by planned C-section, compared to those born vaginally (37 per 1000 children compared to 34 per 1000). Children born by planned C-section were also more likely to receive a prescription for salbutamol – the first-line asthma treatment (103 per 1000 children vs 94 per 1000).

Another important finding of the study was that there appeared to be no link between C-section and an increased chance of being obese by the age of 5. Previous studies have suggested C-section could contribute to obesity in children, but, after adjusting for a number of important factors including the mother’s BMI, level of deprivation and whether or not they breastfed, we found that C-section itself doesn’t appear to increase the risk.

The study also notes a very slight increase in the mortality rate up to the age of 21 years of those born via planned C-section, compared to those born vaginally (4 per 1000 children compared to 3.2 per 1000 respectively) but caution is required when interpreting these figures. With regard to the risk of death, we are not suggesting that if your child is born via a planned C-section then the C-section itself will result in them being more likely to die than if they were born vaginally. There are many issues, i.e. why the C-section was performed in the first place that may explain the association. However it does give us cause to investigate this apparent link in closer detail. It is only by exploring the obesity link in a similar way that we have been able to move closer to ruling it out as a risk of C-section birth, and so it is important to look at the mortality rate in greater detail.

Medical Research: What should clinicians and patients take away from your report?

Response: This is an observational study, so we cannot definitively say that the planned C-section is the cause of the small increase in risk of asthma. However, this is a particularly robust piece of research that took several important factors into account, so we are confident in saying the delivery could be playing a role in the development of asthma. The absolute difference in risk to children delivered by planned C-section was very low, so while C-section may play a part in explaining global increases in asthma, it is unlikely to be important enough to influence individual delivery decisions

Childhood health outcomes following planned C-section is an increasingly important area of study and one that, up until the last decade, little research had been carried out into. Prior to 2006, there were virtually no whole country studies on this topic, now there are at least 4 or 5, with ours examining a broader array of outcomes than previous studies. Overall, this study provides some reassurance that offspring delivered by planned C-section are not at substantially higher risk of childhood illness, and our findings regarding death risk require further research

C-section may play a part in explaining global increases in asthma, but overall, this study provides some reassurance that children delivered by planned C-section are not at substantially higher risk of childhood illness, and our findings regarding death risk require further research

Citation:

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Dr Mairead Black MBChB, MRCOG, MSc (2015). C-sections Linked To Small Increase in Childhood Asthma 

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