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  • Writer's pictureDr. H. Singh, ND

How the Microbiome can Affect Miscarriages and Recurrent Implantation Failure

The Vaginal Microbiome has been extensively studied in the changes that occur once a patient is pregnant and the changes that occur as pregnancy progresses. The shift in the microbiome is meant to help protect the baby, reduce the risk of harmful infections, and reduce inflammation in the uterine environment (and therefore reduce the risk of many complications in pregnancy).

How does the Vaginal Microbiome change with Age?

Before puberty, the lining of the vaginal mucosa is quite thin in the low estrogen hormone environment. Estrogen has a role in stimulating the growth and thickness of the vaginal mucosa, and it also makes the environment optimal for glucose-fermenting organisms partially due to the thicker epithelium. Prior to puberty there are many more gram-positive and gram-negative anaerobic bacteria and some aerobic bacteria. At puberty, as estrogen levels begin to spike, there is an increase in the population of lactobacillus spp. The lactobacillus spp. help to maintain a healthy vaginal microbiome by reducing the pH below 4.5 to reduce the growth of harmful bacteria and fungi.There are also populations Candida spp. and Saccharomyces. After menopause, as estrogen levels decline the vaginal microbiome returns to populations similarly found in the prepubescent period.

Changes in the Vaginal Microbiome in Pregnancy

As Estrogen and Progesterone levels soar during pregnancy, the majority of changes that occur in the vaginal microbiome take place in the 1st Trimester. The vaginal microbiome diversity decreases and the population of the Lactobacillus spp. increases. This change helps to facilitate a decrease in inflammation, decrease the possibility of other bacteria and fungi growing and leading to harmful infections, and (in combination with complex interactions with the vaginal microorganisms) reduces the immune response to help keep the baby safe from harm.

This change takes place as a result of a few factors. Particularly the increase in sex hormone production and concentration, modulation of the immune system, decreases insulin sensitivity and increased blood sugar levels, weight changes, dietary patterns, environment (i.e. pH levels) and changes in levels of inflammation.  

How does the Vaginal Microbiome impact risks for miscarriage and implantation failure?

When the microbiome is altered, the condition that develops is called dysbiosis. Any changes in the normal microbiome shifts described above in a healthy pregnancy can lead to an increase in inflammation and increased production of prostaglandins which can elevate the risk for preterm labour, premature rupture of membranes, miscarriage, cervical ripening & shortening, and increase uterine contractility. Many cases of preterm labour, there is no identifiable cause, but intrauterine infection and dysbiosis are found in up to 40% of cases.  

The Role of Probiotics in the Vaginal Microbiome

The impact of probiotics on reproductive outcomes in controversial. In general there are limited small studies evaluating their efficacy on these specific outcomes. However, the research available so far has shown that it is in general safe to use and topical probiotics may be helpful in reducing the recurrence of yeast and bacterial infections in the short-term. Part of the issue with the complications mentioned above is that many cases of asymptomatic infections can lead to the harmful changes mentioned above. 

However, treatment with antimicrobials and probiotics in healthy Women without any prior history of complications has not shown benefit in reducing the risk of complications listed above either. Right now it is recommended to screen for any symptoms associated with some of the common infections and treat prior to trying to conceive or during pregnancy if needed. Common symptoms include clear discharge, foul-smelling discharge, pain during intercourse, itching, or feelings of soreness. 

Treating the infection and potentially utilizing probiotics to help prevent recurrence and support healthy lactobacillus spp. populations may help prevent some of the complications in Patients that are at higher risk or have had a prior history of these complications.

This article is in no way a replacement for medical advice or medical care, it is advised that anyone concerned about their Health should speak with their Naturopathic Doctor. Please discuss with your healtcare provider and only make changes to your medications regimen if recommended by your doctor and under their guidance. 


  1. Bagga, R., & Arora, P. (2020). Genital Micro-Organisms in Pregnancy. Frontiers in Public Health, 8.

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