In what’s believed to be a world-first, a randomised, controlled study to investigate the role of mothers’ bacteria in babies’ early health is about to start at New Zealand’s Liggins Institute.

Babies born by caesarean-section have a greater risk of developing overweight and obesity, asthma, eczema and other allergic disorders in childhood. Scientists believe it is possible that the health-promoting vaginal bacteria that babies are normally exposed to during birth play a role in establishing normal gut bacteria (microbiome) in babies, and in doing so assist in the development of their auto-immune system.

Findings from previous, small studies suggest that what’s commonly called ‘vaginal seeding’ might help babies born by caesarean establish normal gut bacteria. One such study was well publicised and led to people trying vaginal seeding themselves, despite a lack of high quality evidence on benefits and risks. The new study aims to fill this gap.

The ECOBABe study (Early Colonisation with Bacteria After Birth) – will involve 40 sets of twins born by c-section in Auckland over the next 15 months. In each set, one twin only will swallow an oral infusion containing bacteria swabbed from the mother. The study also includes a separate control group of mothers having only one baby vaginally.

Researchers will measure the range and number of gut bacteria in all the babies by analysing their stools (poo). They will also compare the gut bacteria of c-section babies (who either received or did not receive their mother’s bacteria) and vaginally born babies, to see whether there are differences. They will also measure the babies’ weight, height and body fat composition. 

"If the treatments with the mothers' microbiome actually improves the health and wellbeing of the children in terms of obesity and asthma, it's going to be a simple thing to scale up and do," says study lead Professor Wayne Cutfield, from the University of Auckland-based Liggins Institute.

He explains that babies are born with next to no bacteria in their gut. During vaginal birth their mother’s bacteria colonises them, forming the basis for the baby’s own microbiome – the total bacteria that live inside and on the surface of our bodies, now recognised as playing a crucial role in our health and wellbeing.

“But babies born by c-section are colonised with the other bacteria they come into contact with in the community – from surfaces they touch, from other people’s hands. These bacteria may not have the same health-promoting qualities,” Professor Cutfield says.

Co-researcher Celia Grigg, a midwife and research fellow at the Institute, says, “Many women and midwives are aware that caesarean section disrupts the normal process, and when it is necessary, they want to minimise negative impacts for babies, where possible. People have said to me ‘it just makes sense, even if it sounds a bit weird or artificial’.”

She says there is no evidence to date that the practice is unsafe. “The babies would have been exposed to the same bacteria for a much longer period if they had been born vaginally. Although, as this is research, we are doing extra screening for women in the study.”

Latest provisional figures from the Ministry of Health show there were 16,423 c-section births in Aotearoa New Zealand last year (25 percent of all live births), and that c-section births have reached 36 percent in Auckland City Hospital, a large referral centre.