The way we enter the world has implications for our immunity. A couple of epigenetic studies have recently provided evidence of differences in gene expression between babies born by caesarean-section and those born vaginally: certain genes associated with immunity were being silenced, through the addition of chemical — or epigenetic — ‘tags’ attached to their DNA.
This work was seized upon by researchers at Western Sydney University, who wanted to examine the effect of these findings on long-term health. “It was a big wake-up call for us,” says Hannah Dahlen, a professor of midwifery at Western Sydney University and practising midwife. In Western countries like Australia, the rate of vaginal births without intervention, has sharply decreased in recent decades, as C-sections and other medical interventions have become more commonplace. But most research had focussed on the immediate physical outcomes of different types of birth.
“Nobody other than a small number of epidemiologists had gone further down the track and asked: does the way you’re born matter to your future health?,” says Dahlen.
Within two years, Dahlen and her collaborators published the EPIIC (Epigenetic Impact of Childbirth) hypothesis. EPIIC reframed labour as a critical life event, proposing that the stresses of a vaginal birth, without drugs or instrumental interventions, leave their mark on a baby’s genome, priming it for a healthy life outside the uterus. Too little stress (in the case of C-section-born infants) or too much stress (during an augmented or instrumental delivery) might alter how these marks are laid down, with implications for the child’s future health.
A second hypothesis is the extended hygiene hypothesis (EHH) and focus on disturbance of the microbiome. The use of prophylactic antibiotics during a caesarean section and not being born through a bacteria-rich vagina can affect the composition of the microbiome — the community of microorganisms living upon and within us — that becomes established in the baby’s body shortly after birth, which may in turn lead to changes in how the immune system develops. It is probably an interaction of these two factors that is at play here, though more research is needed to show a causal relationship.
At first, the EPIIC hypothesis received a lukewarm reception: “We basically got laughed out of town by the medical profession,” Dahlen says. However, as people become more aware of the importance of the microbiome and understanding about epigenetics expanded attitudes began to change. “Now when we present this at conferences I see a lot of nodding heads,” she says.
The EHH hypothesis also written about by Dahlen and colleagues proposes that during a vaginal birth, babies become coated in their mother’s bacteria, some of which inevitably get swallowed and begin to colonise their gut. Breastfeeding provides another source of beneficial bacteria.
It is looking like epigenetics and the microbiome may both prime the immune system and affect the long-term health of the baby, child, and future adult but more work is needed in this area and Dahlen’s team is working on this important question.
Premature birth, maternal anxiety during pregnancy, and postnatal environmental effects, may also influence a baby’s future health. Dahlen recently published research suggesting that maternal anxiety during pregnancy, together with birth by C-section, or premature birth, are major predictors of a baby suffering from reflux during its first year of life.
In another study, Dahlen and colleagues examined epidemiological data from hundreds of thousands of babies born in New South Wales discovering that those born by spontaneous (without intervention) vaginal birth had fewer short- and longer-term health problems during their first five years of life, including infections, eczema and metabolic syndrome, compared to babies born after medical interventions, particularly C-sections.
Need to know
- Birth method can lead to differences in gene expressions.
- The EPIIC hypothesis posits childbirth is a critical life event.
- Mothers transfer beneficial bacteria to babies during a vaginal birth.
Providing a better start to life
So, if a vaginal birth without instrumental or drug interventions is best for babies, how do we ensure that more are born safely this way?
One solution is to provide women with access to the same midwife throughout pregnancy and birth. Dahlen believes that this could help reduce the number of medical interventions during birth. A recent systematic review concluded that continuity of midwife care increases the likelihood of a spontaneous vaginal birth and decreases premature births, although it has no effect on C-section rates.
“Probably the biggest benefit is having someone who knows your history,” says Jennifer Lorence, a Sydney woman whose delivery of her fourth daughter, Alice, was supported by Dahlen last summer. Prior to this she had experienced two miscarriages, which Dahlen also helped support her through. Such relationships, built on trust and experience, are a hallmark of midwife-led continuity of care – and, in Jennifer’s case, helped her feel more relaxed in the run-up to labour, and during the birth itself: “It’s the face-to-face contact and all the conversations that you’ve had about how you’re feeling, your family situation, and your children”.
As for providing babies with the best start to life, Dahlen suggests: “Getting to know women during their pregnancy, only stepping in when needed during labour, keeping mothers and babies together following birth, and making sure that we provide women with enough support to get the best out of themselves.”
Meet the Academic | Professor Hannah Dahlen
Hannah Dahlen is a Professor of Midwifery and Higher Degree Research Director in the School of Nursing and Midwifery at the Western Sydney University. Hannah has had national and international success with grants (three NHMRC, one ARC, two COST). Hannah has published more than 100 papers and has given papers at over 100 conferences and seminars with half of these being invited keynote addresses. Hannah is one of the top ranking Western Sydney authors for The Conversation. Hannah has been cited in the media over 1000 times and has been a part of three documentary films. Hannah has strong international collaborations. She is co-founder of the international research collaboration EPIIC (Epigenetic Impact of Childbirth). In November 2012 she was named in the Sydney Morning Herald’s list of 100 "people who change our city for the better". She was named as one of the leading "science and knowledge thinkers" for 2012 due to her research and public profile. Hannah has a strong profile in the profession of midwifery. She is a past National President of the Australian College of Midwives and she sits on several peak National and State committees. Hannah sits on several state and National Health committees. Hannah is still a practising midwife and works in a private group practice in Sydney.
Higher Degree Research at Western
This research was supported by the Australian Government through the National Health and Medical Research Council.
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Future-Care is published for Western Sydney University by Nature Research Custom Media, part of Springer Nature.