Probiotics could help women avoid postnatal depression, a New Zealand study has found.

Taking a probiotic tablet once a day during pregnancy and in the first six-months after birth halved a mother's risk of clinically significant anxiety, the research found.

With 10 to 15 per cent of women being affected by depression or anxiety during or after pregnancy, it was a hugely important discovery, said lead-author Dr Rebecca Slykerman.

Slykerman, of Auckland University's faculty of health sciences, said even the research team was surprised by how much of a difference the probiotic, Lactobacillus rhamnosus HN001, made.

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The Probiotics in Pregnancy Study, funded by the Health Research Council and Fonterra Co-operative Group Limited and carried out between 2012 and 2014, recruited 423 women in Wellington and Auckland who were between 14 and 16 weeks of pregnancy and put half on the probiotic and half on a placebo.

The study found mothers in the probiotic treatment group reported significantly lower depression and anxiety scores than those in the placebo group and rates of clinically relevant anxiety were halved among the probiotic treated mothers.

Professor Ed Mitchell, who led the mental health aspect of the study, said postnatal depression was associated with persistent depression and, in a few cases each year, suicide but could also impact on the long term wellbeing of the baby.

"There is mounting evidence from animal studies that the microbiome-gut-brain axis - the biochemical signalling that takes place between the gastrointestinal tract and the central nervous system - may be important for mental health," he said.

Pregnant women and breast-feeding mothers were often reluctant to take anti-depressants, Slykerman said, so the results were significant because taking a probiotic was a safe, cost-effective, easy to use, easily available treatment which women might be more happy to take.

But, being the first study of its type, more research needed to be done to replicate the results, look at whether other probiotics had the same effect, what dosage was needed and how long the treatment needed to continue for, Slykerman said.

Mother's Helpers founder Kristina Paterson holds five pairs of babies' booties to represent the number of infants affected by maternal suicide on average every year in New Zealand. Photo/File
Mother's Helpers founder Kristina Paterson holds five pairs of babies' booties to represent the number of infants affected by maternal suicide on average every year in New Zealand. Photo/File

Kristina Paterson, an advocate for mental health among mothers, said it was good to see research being done on ways to prevent postnatal depression rather than just treat it.

"If preliminary studies are showing that this could help, we should invest in further research to see whether it does have a significant impact."

About 11,000 New Zealand women suffered from perinatal depression, she said, which could have a considerable and sometimes life-long impact on both mother and child.

"If we could prevent it happening, that would be great," she said.

It was Paterson's own battle with postnatal depression which pushed her to set up Mothers' Helpers and the Maternal Care Action Group to provide support and help to other women going through the same thing.

Severe postnatal depression could put children at risk of emotional, cognitive, behavioural and attachment issues as well as learning difficulties, mental health and addiction issues and a higher risk of suicide, she said.

About five infants were affected by maternal suicide, either during pregnancy or soon after birth, every year in New Zealand, she said.

Mother-of-two Miriam Wood took part in the trial while she was pregnant with her first child.

She was given the placebo and did not face any anxiety or depression.

Wood said, as a psychologist, the results were fantastic news.

"It's such a vulnerable time for women," she said.

"We have quite a different view of probiotics. It's seen as something more natural and there's no stigma associated with it."

• Lactobacillus rhamnosus HN001 is not yet commercially available through Fonterra yet but can be purchased as GO Derma Protect online or in pharmacies for as little as 50 cents a tablet.

What are probiotics?

• Probiotics are live micro organisms that when consumed in adequate amounts provide health benefits to the host - especially your digestive system.
• They are found in some yoghurts and other fermented foods.
• They are commonly used to treat irritable bowel syndrome, inflammatory bowel disease, infectious diarrhoea (caused by viruses, bacteria, or parasites) and antibiotic-related diarrhoea.