Aug 28, 2014
The debate about the relative benefits and disadvantages of Caesarean Sections versus vaginal births is one of the most complex and contentious in the medical and health sphere. In this fascinating piece, Hannah Dahlen, Professor of Midwifery, University of Western Sydney, approaches this issue from a microbiological and epigenetic perspective and discusses the evidence for a causal link between labor and birthing processes and diseases later in life, such as asthma and diabetes. These fields of research are relatively new and not without their skeptics. However, if proven to be correct this research could potentially have major implications for birthing practices in countries, like Australia, with very high rates of Caesarian sections, and provide important insights into the cause of the ‘chronic disease epidemic’ facing our society today. Professor Dahlen writes:
In 1915, when caesarean section was rare, Kendall proposed that microbes, which colonise the baby’s gastrointestinal tract following vaginal birth, ‘may be protective’ He said, “Very shortly after birth bacteria make their appearance in the mouth of the newborn, and organisms appear in the meconium from four to twenty hours post partum (Kendall, 1915 p 209). Colleagues of Kendall had previously undertaken experiments sterilizing the environments (including undertaking caesareans) and foods of newly born/hatched animals, observing that development became affected under these conditions. This led Kendall to conclude that these bacteria may be protective under ‘ordinary conditions’.
In the intervening 100 years intervention in childbirth has climbed higher than ever before in the history of humankind. Vaginal births without a medical intervention are becoming increasingly rare in both Australia and many other developed nations. In 2012 we published a paper showing only 15% of low risk first time mothers giving birth in private hospitals in NSW did so without intervention compared to 35% in public hospitals. In 2014 we published a follow up paper showing that babies born to low risk women in the private sector, where the intervention rates were so much higher, were more likely to have a problem following birth and to be readmitted to hospital in the first 28 days for morbidities associated with interventions, such as forceps and vacuum birth (scalp trauma) and being delivered early (breathing difficulties, feeding difficulties, sleep and behavioural difficulties and jaundice). However this is only giving us a short-term glimpse at the impact of obstetric intervention.
Despite efforts nationally and internationally to reduce intervention rates during childbirth medical intervention is becoming the norm. In Australia one in three women now give birth by caesarean section (nearly 1:2 in the private sector); more than half are induced or have their labour sped up with drugs; and around 50% are given antibiotics to reduce the risk of infection. In some countries such as China over 50% of women now give birth by caesarean section. The World Health Organisation (WHO) estimated the cost of unnecessary caesarean sections at US $2.34 billion globally in 2008, with 6.20 million unnecessary caesareans being performed annually. WHO stated again in 2010 that caesarean section ‘rates >15% may result in more harm than good.’ Of all the developed nations in the world Iceland comes closest to meeting this target (17%) and also has the lowest numbers of babies and mothers dying in the world. Never before in human history has there been such a dramatic uncontrolled and unevaluated experiment in progress for so long.
Much of the research on the effects of intervention during birth has focused on the short-term outcomes of mother and baby. But what if unknowingly society is being reshaped on a microbiological and epigenetic level through the way women give birth and could this be having long-term health effects? We have just addressed this question in a commentary published in Midwifery and we propose the evidence is mounting but the response continues to be muted.
Microbiologists are studying physiological processes beginning during pregnancy birth and breastfeeding and neonatal gut flora. This gut flora that has been inherited across generations from Neolithic times, and a co-dependency has built up between these organisms and the human immune system. Loss of the usual labour and breastfeeding route of colonisation leaves a baby vulnerable to later auto-immune disease. A study published recently using DNA sequencing showed babies born by elective caesarean section lacked or had lower numbers of certain bacteria that are found in babies born vaginally. And we know disrupting gut microbes has been linked to a range of diseases, such as inflammatory bowel disease, allergies, asthma, cancer, and so on.
An alternative explanation, or possibly a co-occurring mechanism, focussed on the stress response and the role of epigenetics in gene expression. Scientists are increasingly realising that the genetic legacy we pass on to our offspring is not fixed. While we are all born with a unique gene profile, we now know that how our DNA is expressed depends on several environmentally triggered, epigenetic processes, such as DNA methylation, which involves silencing or switching off of whole, or parts of, individual genes so that they cannot function, thus altering gene expression. Genes and susceptibility to disease can be activated or deactivated by lifestyle factors and experiences such as diet, stress, exposure to toxins – and childbirth. This relatively new field of study is called epigenetics, which literally means above of or on top of genetics.
In January 2012 we brought together eleven researchers (midwives, scientists, epidemiologists, geneticists and epigeneticists) and developed the EPIIC Hypothesis, which was published in the journal Medical Hypothesis. We hypothesise that events during labour and birth – specifically the use of the synthetic hormone oxytocin along with antibiotic use and caesarean sections – affect the epigenetic remodeling processes and the subsequent health of the mother and child.
In the EPIIC hypothesis, we propose that physiological labour and birth have evolved to exert eustress (a healthy, positive form of stress) on the fetus, and that this process has an epigenomic effect on particular genes, particularly those that program immune responses. Reduced or elevated levels of the hormones cortisol, adrenalin, and oxytocin which are produced during labour may lead to fetal epigenomic remodelling anomalies which exert influence on abnormal gene expression. This reprogramming could manifest in a range of diseases and behavioural problems in the neonate and later on in the adult. This suggests that what goes on in labour and birth may be crucial to epigenetic remodelling.
In a recent comparative study, Swedish researchers found that certain cord blood cells of infants born by caesarean section had more global DNA methylation than those from infants born vaginally. There was also a relationship between the length of labour and methylation in some genes. The researchers suggest that the potential for adverse effects (such as disease) can lie dormant, unless or until a specific trigger acts on genes through these epigenetic processes. This would explain why labour and birth events are associated with far-distant chronic (especially auto-immune) disease states such as asthma and diabetes.
Due to a dearth of research in this domain, epigenetic changes which may occur due to medical interventions and environment interactions remain unknown, as well as the health implications for mother and child. The evidence around the seeding of the neonatal gut with healthy bacteria during birth and following birth with breastfeeding is mounting and very concerning.
Remarkably, 100 years after Kendall published his observations, vaginal swabs are now being taken from some women giving birth by caesarean section and smeared on their nipples or onto the baby’s face and lips to help seed the baby with important bacteria. As we continue to test this hypothesis, hopefully we’ll come closer to determining whether society is indeed being reshaped on a microbiological and epigenetic level by the way women give birth and how these two hypothesis may interact.
A major documentary Microbirth will be launched internationally on the 20th September 2014, exploring the evidence for, and implications of, both the microbiological and epigenetic hypotheses and the implications of changing birth practices for society as a whole.
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