The establishment and development of the microbiome in the early stages of life can play a pivotal role in affecting our health throughout life. The formation of our microbiome happens during the perinatal period where it is influenced by the interaction between the microbiomes of mothers and infants. The microbial composition of breast milk plays an important part in this process. The microbiome of breast milk is also influenced by the gut microbiome of the mother through what is termed the gut-breast axis. In this podcast, I’ll explore these mother-infant microbiome links and discover what the scientific evidence has to say about the potential for maternal probiotic supplements having a positive influence on the health of mother and infant.
The seeding and development of the microbiome early in life has the potential to shape our cognitive and immune system development and influence lifelong health. So what exactly is the microbiome? It is the community of microorganisms such as fungi, bacteria and viruses that exist in a particular environment. It is the gut microbiome you hear about the most, but that is far from the full story. We have microbiomes as part of our skin, mouth, lungs, eyes, nasal passages and along the urogenital tract.
The maternal microbiome plays a big part in seeding the newborn with its microbiome as there is transfer happening during pregnancy and birth as well as through breast milk and the skin contact from breastfeeding. Breast milk is a complex system as it contains microorganisms vital for establishing the infant's microbiome. It is called the gut-breast axis and involves cells that transport beneficial bacteria from the woman’s gut to the mammary system which then supports the newborn's nutritional and immunological needs.
So what role for probiotics in supporting and augmenting this natural system? Probiotics are beneficial microorganisms that can be taken during pregnancy to address gut issues and some other pregnancy related complications of the mother. The breast milk microbiome is thought to be a potential pathway for transferring the probiotic-altered gut microbiome from mother to newborn.
So it is timely that only in the last few weeks, a systematic review and meta-analysis has been published that explored the effects of maternal probiotic supplements on the breast milk microbiome and the infant gut microbiome and health.
The review included published randomised controlled trials on the effect of maternal probiotic supplementation (either as single-strain or multi-strain formulations) taken during pregnancy and lactation and what it did to breast milk and the infant gut microbiome composition as well as the infant’s health. All trials included a placebo group.
All up, 24 trials were included involving over 2,700 mothers and over 1,700 infants. And I’ll link to the review in the show notes. https://www.ajogmfm.org/article/S2589-9333(23)00290-2/fulltext
So let’s dive into what the review uncovered. Probiotic supplementation during the perinatal period (so that is during pregnancy and post-pregnancy) was able to alter the microbiome of breast milk with a higher detection rate of beneficial bacteria by 24 percent and a greater abundance of these bacteria together with reduced pathogenic bacteria.
And for the infant, there was evidence that their gut microbiome profile was also remodelled through breastfeeding which translated into benefits on normalising weight gain meaning there was less excessive weight gain linked with obesity. To add to this, there was also a reduction in the occurrence of infantile colic by 70 percent.
The question I’m sure you’re wanting to ask is what sort of probiotics were taken by the women? It was a pretty wide spectrum and included bacteria from the genera of Lactobacillus and Bifidobacterium as the most commonly used, but some trials used the species of Streptococcus thermophilus and Saccharomyces boulardii.
And to add to all this, all included studies bar one found that beneficial bacteria were detected in a greater number of participants in the probiotic groups than in the control groups.
Of special note, none of the included studies reported any adverse events in the mothers or infants from taking probiotics.
That last point about safety is a nice segue into a bubbling issue to do with probiotics during pregnancy. The issue exploded in September of 2022 when there was quite a bit of press about a finding from a Cochrane review that looked at the effect of probiotics on the risk of gestational diabetes as its primary focus. The review came up with an observation that some women appeared to have a greater risk of pre-eclampsia when taking probiotics. I’ll link to this review in the show notes. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD009951.pub3/full
So are these probiotic supplements a double-edged sword for women who are pregnant and are best avoided? Not so fast. Reading past the headlines and social media posts about this finding to do with preeclampsia, the reality is a lot less concerning.
For a start, the Cochrane review was about gestational diabetes, so you should always be cautious about findings that were not the primary focus of a study. And that higher risk of pre-eclampsia was only seen in studies with women who were obese - a factor that significantly ups a woman’s risk of pre-eclampsia to begin with. And there were only 4 studies to make this conclusion from, involving just 411 women.
While the results did show a significant increase in pre-eclampsia risk in women who were obese from taking probiotics, the overall incidence was still within the expected rate of about 10 percent for women who are obese. So while the stats said there was a significant difference, when you looked at the absolute number of cases in the placebo versus the control group you end up making a comparison of 31 cases of preeclampsia in women taking probiotics and 17 cases in women taking a placebo.
It certainly is plausible that all that was seen was natural statistical variability where a few cases either way would change the finding. This would be very different if you scaled this up 10-fold and saw 310 cases in the probiotic group and 170 cases in the placebo group – the same relative proportions but very, very unlikely to be a result of natural statistical variation.
I’ve given this commentary on the 2022 Cochrane review more for being cautious in that if there are serious adverse health risks of taking probiotics during pregnancy in a sub-group of women who are obese, it will take stronger research to confirm this in the future. While today we can point to the health benefits of taking probiotics as potentially outweighing that.
So, let’s wrap all this up. From this latest research I’ve profiled, rather than being an overall recommendation for probiotics during pregnancy, it reinforces the benefits of breastfeeding for improving the gut health of neonates with the milk microbiome an essential route for mother-to-infant bacterial transmission. Whether a woman should take probiotics during the peri-pregnancy period for this or other health reasons is a personal decision that is best made after talking to your health care provider.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.