By Ana Espino | Published on February 18, 2026 | 3 min read
Recurrent pregnancy loss (RPL)
affects approximately 1–2% of women of reproductive age and represents a major
issue in gynecology and obstetrics. It is defined as the occurrence of at least
two consecutive pregnancy losses before 20 weeks of gestation. Although certain
causes have been identified (chromosomal abnormalities, coagulation disorders,
immunological factors), in nearly 50% of cases no clear triggering factor is
found, which considerably complicates management.
Currently, therapeutic approaches
remain fragmented and often empirical, combining hormonal treatments,
antiplatelet agents, or immunomodulators without robust evidence of
effectiveness for all patients. This uncertainty reflects the limitations of
the current biomedical model, which often overlooks environmental and
microbiological factors.
Among emerging avenues of research,
the vaginal microbiota has attracted growing interest. Under normal conditions,
an ecosystem dominated by Lactobacillus spp. provides protection against
infection and maintains an acidic pH favorable to implantation. In contrast,
dysbiosis—marked by the proliferation of anaerobic bacteria such as Gardnerella,
Prevotella, or Atopobium—may promote inflammation, disrupt the
maternal–fetal interface, and increase the risk of fetal loss.
In this context, the present study
was initiated to analyze the role of the vaginal microbiome in recurrent
pregnancy loss. The associated inflammatory, metabolic, and immune mechanisms
were investigated. The objective was to evaluate therapeutic prospects,
particularly through targeted modulation of this ecosystem.
What if miscarriage originated in
the microbiota ?
This study is based on the analysis
of vaginal microbiota composition, its derived metabolites, associated immune
profiles, and their link with recurrent pregnancy loss. The selected studies
include cervicovaginal sampling analyses, 16S rRNA sequencing, measurement of
pro-inflammatory cytokines, and clinical cases of vaginal microbiota
transplantation.
The results reveal that patients
with RPL show a marked reduction in Lactobacillus species, with a
predominance of potentially pathogenic bacteria such as Gardnerella
vaginalis, Anaerobacillus, or Streptococcus. This imbalance
is accompanied by an altered metabolic profile, with decreased protective
lactate and increased pro-inflammatory biogenic amines, an exacerbated local
inflammatory response (elevated IL-6, IL-8, TNF-α), and the presence of a bacterial biofilm
resistant to standard antibiotic treatments. These changes lead to detrimental
uterine immune activation, compromising maternal tolerance to the embryo and
promoting implantation failure. Some studies highlight the potential of vaginal
microbiota transplantation to restore a healthy ecosystem in refractory
patients, opening the way to an innovative and personalized therapeutic
strategy.
Rethinking miscarriage in the era of
the microbiome
Recurrent pregnancy loss is a common
multifactorial condition, with unexplained etiology in nearly half of cases.
The main clinical challenge lies in the absence of reliable predictive
biomarkers and targeted treatments for these idiopathic forms. This study aimed
to explore the role of the vaginal microbiota in the development of recurrent
pregnancy loss, drawing on metagenomic, immunological, and clinical data.
The findings suggest that microbial
imbalance, characterized by reduced Lactobacillus and increased local
inflammation, may disrupt the uterine environment and compromise embryonic
implantation. This hypothesis paves the way for new therapeutic strategies
focused on microbiome modulation.
However, limitations remain and
justify further research. Additional clinical trials are needed to test the
efficacy of vaginal microbiota transplantation, better standardize analytical
methods, and identify reliable markers to predict risk. It will also be
important to better understand the link between the vaginal microbiota and
immunity, and to assess the impact of microbiome-based treatments on pregnancy
rates and long-term neonatal health. These efforts may enable the integration
of such approaches into more personalized and preventive care strategies.
About the author – Ana Espino
PhD in Immunology, specialized in Virology
As a scientific writer, Ana is passionate about bridging the gap between research and real-world impact. With expertise in immunology, virology, oncology, and clinical studies, she makes complex science clear and accessible. Her mission: to accelerate knowledge sharing and empower evidence-based decisions through impactful communication.
