New Tommy’s research suggests link between miscarriage and bacteria in the vagina

Around 1 in 5 pregnancies end in miscarriage, which has a huge effect on both mental and physical health. One of the main problems with preventing miscarriage is that, in many cases, we don’t know or understand the cause. Even if we can’t prevent a miscarriage, understanding what caused it can help parents to come to terms with their loss and reduce the impact it has on their mental wellbeing.

Half of early miscarriages happen because of chromosome abnormalities in the baby, but in the other 50% of miscarriages, something else must be going on. Researchers at our National Centre for Miscarriage Research have been working hard to understand what the possible causes might be – and a new study by the team in London suggests there is a link between miscarriage and a lack of certain bacteria in the vagina. 

What was the study about?

The vaginal microbiome is an environment of microorganisms which live inside the vagina. A healthy vaginal microbiome is mainly made up of a type of bacteria called lactobacillus. This helps maintain a healthy balance of microbes by preventing the growth of other potentially harmful bacteria.  

There is growing evidence to suggest the way a pregnant woman’s immune system interacts with the bacteria in her vagina can cause a miscarriage. To investigate this link, the team at our National Centre for Miscarriage Research decided to study the vaginal microbiome of women who had a miscarriage and women who had a full-term pregnancy, comparing samples of their vaginal fluid to see if there were any differences. 

What our experts found

The results were based on 167 women, where 93 pregnancies ended in miscarriage and 74 went to full term. Where women had a miscarriage, the team tested the placenta to find out whether the loss was associated with a chromosomal problem or not. They found that in pregnancies which were chromosomally normal, miscarriage was associated with a vaginal microbiome which was low in lactobacillus. Some of the women who gave birth to a healthy baby also had a vaginal microbiome lacking in these bacteria; what seemed to make the difference was how much the mother’s immune system reacted towards the vaginal bacteria. 

Why this research matters

The team’s findings present a fresh perspective on underlying issues that can lead to miscarriage – and which may be treatable – but further studies are needed to validate what they’ve found and understand what triggers this immune response.

As the balance of bacteria in the vagina is something which can potentially be identified and then corrected, they’re now working on a method to analyse vaginal bacteria rapidly in healthcare settings. This could identify a group of women and birthing people who would benefit from antibiotic or pre- or probiotic treatment to reduce their risk of miscarriage. An important next step is to look at treatments that could help maintain a healthy balance in the microbiome and improve someone’s chance of carrying their baby to term.

In the meantime, this study highlights the importance of good vaginal health in early pregnancy, and there are some things pregnant people can do to support this. It's a good idea to avoid perfumed soaps, gels and antiseptics as these can affect the healthy balance of bacteria and acid levels. The vagina is designed to be ‘self-cleaning’ so using products like these can be irritating, even if they’re marketed as female hygiene products. You can clean around the area, which is called the vulva, using gentle, unscented soap, but you should avoid douching or washing inside your vagina.  

For women who are trying to get pregnant and are still having periods, keeping the area around the vagina clean is important but, again, the use of scented or antibacterial products and washing inside the vagina should be avoided. During your period, washing your vulva and the area between your vagina and bottom more than once a day with a gentle soap and water may be helpful, but it’s best not to use douches because this can disrupt the normal vaginal bacteria.

For more advice on what you can do to help your chances of a healthy pregnancy, visit our PregnancyHub.