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The Auckland study pregnant women will be watching

Fears and guilt about C-section births have helped “vaginal seeding” spread, despite there being little evidence that it works. A new study in Auckland could help change that, reports Eloise Gibson.

During filming of a recent documentary, conversation turned to a topic that might have once been considered shocking.

Several members of the crew had heard of a practice called vaginal seeding, and some of their wives had tried it.

Vaginal seeding, for the uninitiated, involves swabbing a woman’s nether regions and swiping the goo on the face and body of her newborn, in a bid to give the baby a full, healthy set of microbes.

In the course of a few decades we have gone from trying to rid ourselves of bacteria, to loving them, to smearing them on newborns.

But the practice is also born of maternal worry, high caesarean rates, studies linking C-sections with obesity and immune system problems and, of course, the internet, which tells any pregnant woman who Googles that her baby may miss out on essential gut microbes by skipping the birth canal.

The trend for vaginal seeding is spreading despite any clear evidence that it works.

One of the few attempts to test it was a trial in Puerto Rico, which made it into the influential journal Nature despite involving just 18 babies – only 4 of which received the treatment.

While many doctors see no harm in facilitating a bit of bug smearing, some top obstetricians warn against it. Newspapers in Canada and the U.S have reported the risk of transmitting infections such as chlamydia, Group B Streptococcus or gonorrhoea.

In 2016 physicians from three British hospitals explained in the British Medical Journal that they wouldn’t support it, because the small infection risk wasn’t countered by any real evidence of benefit.

Despite the risks and dearth of studies, women in the U.K., U.S, Denmark, Australia and New Zealand are still requesting seeding from their doctors. Midwives have been known to delicately allude to “DIY” seeding during antenatal classes. One Auckland obstetrician told Radio New Zealand that one in twenty of his caesarean patients asks for it.

Another paediatrician told Newsroom he was once “interviewed” by a pregnant journalist, who, it turned out, was not writing anything. She was after the recipe.

Since women are doing it anyway, a new trial at Auckland University's Liggins Insitute is enrolling participants in the hope of gaining more robust evidence.

Researchers are enlisting women for a clinical trial that will eventually include 120 babies: 40 sets of caesarean-born twins and 40 vaginally-delivered singletons.

The results won’t be out for more than a year, but, when they are, they are likely to gain attention.

Would-be mothers will be first screened for transmissible illnesses, to prevent infecting babies. If they get the all-clear, nurses will take a vaginal and perineal swab, mix the microbes with sterile water and put the mixture in a syringe so babies can swallow the liquid. Delivering the microbes down to the gut is different from the typical swab-and-smear tactic, which lead researcher Wayne Cutfield likens to throwing seeds on a motorway and hoping a tree grows. “Yep, there’s a shot, it’s possible there’s a crack in the tarmac but there’s a much better chance if you dig a hole and add fertiliser,” he says.

One twin in each set will get an oral infusion of its mother’s microbes. The other twin will get a placebo of plain liquid. The third group, made up of vaginally born babies, will get whatever they happen to swallow on their way through the birth canal.

After three months (and some unenviable nappy-sampling) the researchers will compare the micro-biomes from the three groups to see if the twins who received the seeding are closer in their microbial make-up to the vaginally-born babies.

They hope to follow the children until their early school years, to track their rates of obesity and various health issues.

The trial has already confronted ethical questions, like, is it okay to give one twin a treatment that might benefit them, but not the other twin?

Cutfield says that when Liggins surveyed prospective mothers, most of them said that, while not ideal, it was better to have one twin treated than neither. Most women also thought it was an important study, making them supportive of the planned trial.

Cutfield explains that infants in utero have mostly sterile guts. They don’t get their suite of internal microbes until during and after birth. If they don’t pick up their mum’s micro-biome, “they might become colonised by bacteria from out in the community, which might be less ideal,” says Cutfield. Babies have only a short period after birth during which bacteria can establish themselves, before their stomachs get too acidic to welcome new populations.

What happens during that window might be important.

About a third of Auckland babies are born by caesarean, and globally the rate is about one-fifth.

A growing body of research links deficiencies in our micro-biomes to a surprisingly long list of health issues, including mental illness, pain and auto-immune disorders, such as diabetes and Coeliac disease. “Fifteen years ago we didn’t think gut bugs influenced our health at all, we saw them as squatters,” says Cutfield. “We now see them as valuable tenants.”

Although studies show an association between C-sections and an increased risk of some health problems, they don’t prove those issues are caused by caesarians, let alone by microbial differences from caesareans. But doctors are keen to explore the reasons why there might be a statistical link, and microbes are a prime suspect.

“There are a number of epidemiological studies suggesting babies born by caesarean may be disadvantaged in the long-term, and the two obvious things that have been looked at are childhood obesity and asthma and allergic diseases,” says Cutfield. “They have a 30 percent increased risk of childhood obesity and when you consider the environment we live in, where one in three children getting ready to start school are overweight or obsess, that’s a major problem,” he says.

Whether the finished trial supports vaginal seeding or finds no benefit, it may give women more evidence to help them make choices. Other practices, like skin-to-skin contact with newborns and breastfeeding, can also pass on a mum’s microbes. As for seeding, the jury’s out, and will likely remain so for a while.

“If it turns out that it is effective, it’s an easy thing to scale and implement, and midwives and obstetricians could do it,” says Cutfield. “But if it doesn’t make a hoot of difference, let’s stop the hoo-haa.”

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