Can seeding prevent cancer?
News that babies who miss out on microbes could be more at risk of childhood cancer has shed a new spotlight on the practice of seeding.
According to scientists at the Institute of Cancer Research, a lack of exposure to ‘good’ bugs in the first year of life fails to teach the immune system to deal with threats correctly. In children pre-disposed by genetic mutation, this sets the stage for an infection to come along in childhood, cause an immune malfunction and leukaemia.
Work by Professor Mel Greaves published in Nature Reviews Cancer 1 will need further research, but it has revived debate about the controversial idea of seeding.
What is seeding?
Seeding is a way of exposing babies born by C-section to beneficial bugs that other babies pick up as they travel through the birth canal during a vaginal birth.
There is research to show that babies born by Caesarean have slightly different gut bacteria to babies born vaginally, because they do not become ‘colonised’ with their mother’s ‘good’ vaginal bacteria.
This may be a reason why C-section babies are slightly more likely to develop conditions such as asthma, food allergies, hay fever and obesity than babies born vaginally. Additionally, there is evidence of lower rates of leukaemia in children born vaginally than by C-section, which transfers fewer microbes.
Seeding is said to help babies born by Caesarean to gain the potential benefits of their mother’s vaginal bacteria. One idea has been for the mother to place a sterile muslin in her vagina for one hour before the birth to absorb bacteria. It is then wiped over her newborn’s face, mouth and hands.
Is there any research evidence for seeding?
Currently, there is not enough research evidence available to prove that seeding has benefits. A five-year study began in 2015 to see whether it is safe and beneficial. New Scientist magazine reported in 2016 that a study on a very small number of babies in New York treated by seeding found a shift after 30 days towards gut bacteria normally found in babies born vaginally 2. Scientists are now studying whether the changes last, and if they are enough to prime the immune system.
We know that humans depend on a vast number of microorganisms to stay alive. Our skin, gut and mouth are teeming with microbes that protect us against disease. But because there has been so little research on seeding, we don't know whether it is safe or effective.
What are the risks of vaginal seeding?
The main risk is that babies might get serious infections from the transfer of bacteria including E. coli and Group B streptococcus, and doctors have warned against vaginal seeding in an opinion piece in the British Medical Journal 3. A new Danish study 4 has concluded that the risk is "probably very low" but that "at this point in time, there is no evidence to suggest that the proposed long-term benefits would outweigh the costs and potential risks."
Personally, I feel that seeding is a matter of parental choice and if parents want to pursue this after a Caesarean then they should be supported to do so.
Protection through breastfeeding
Of course, while seeding remains of unknown and only theoretical benefit, what is proven is that the most effective way of developing your baby’s microbiome is by exclusive breastfeeding. Breastfeeding promotes good bacteria in the gut and also protects against leukaemia. The first breastfeed should happen within an hour or two of birth, and your baby should be exclusively breastfed for at least six months. The benefits of breastfeeding to a baby’s immune system are scientifically evidenced, while another way to increase bacteria naturally is through plenty of skin-to-skin contact between mother and baby right after birth.
On a final note, the charity Bloodwise says: "While developing a strong immune system early in life may slightly further reduce risk, there is nothing that can be currently done to definitively prevent childhood leukaemia." So no parent need feel any guilt about the choices they have made.
- Nature Medicine, DOI:10.1038/nm.4039