News | Does the reproductive tract microbiome affect IVF success? Study highlights the key role of Lactobacillus
The human microbiome affects not only gut health but may also have far-reaching effects on fertility. A recent study found that the composition of the female reproductive tract microbiome may directly affect the success of assisted reproductive technology (ART), particularly pregnancy outcomes after in vitro fertilization (IVF).
The study was conducted by Miyagi, Mekaru, Tanaka and colleagues and published in JBRA Assisted Reproduction. It found that a reproductive tract microbiome with a high proportion of Lactobacillus was associated with higher pregnancy rates, while overgrowth of certain pathogenic bacteria may reduce the likelihood of pregnancy.
Lactobacillus and reproductive health: Why does microbial balance matter?
The female reproductive tract microbiome is usually dominated by Lactobacillus. These bacteria help maintain an acidic vaginal environment and inhibit harmful bacteria, and may also improve endometrial receptivity. However, when Lactobacillus levels fall and pathogenic bacteria such as **Gardnerella vaginalis, Enterococcus, Streptococcus and Staphylococcus** increase, embryo implantation may be affected and early miscarriage may even occur.
Study background: The team analyzed 35 women undergoing ART. Next-generation sequencing (NGS) was used to assess their vaginal and endometrial microbiomes and examine how the proportions of Lactobacillus and pathogenic bacteria affected pregnancy outcomes.
All participants received high-quality embryo transfers (ET), and all had an endometrial thickness of at least 8.0 mm, helping ensure that outcomes were influenced as much as possible by microbiome factors rather than embryo quality or uterine conditions.
Participants were divided into four groups according to high or low levels of **Lactobacillus (L) and pathogenic bacteria (PB)**:
High L/low PB (Lactobacillus-dominant, fewer pathogenic bacteria) High L/high PB (high levels of both Lactobacillus and pathogenic bacteria) Low L/low PB (lower Lactobacillus, fewer pathogenic bacteria) Low L/high PB (lower Lactobacillus, more pathogenic bacteria)
Results: Higher pregnancy rates in Lactobacillus-dominant groups
Among 34 embryo transfers, 21 resulted in pregnancy; 17 led to delivery and 4 ended in early miscarriage.
Women who became pregnant had Lactobacillus-dominant vaginal and endometrial microbiomes, while pathogenic bacteria predominated among those who did not become pregnant.
Comparison of microbiome composition showed that:
Pregnancy rates increased significantly when Lactobacillus accounted for ≥46% of the vaginal microbiome and ≥55% of the endometrial microbiome.
Conversely, pregnancy rates fell significantly when pathogenic bacteria accounted for ≥18.7% of the vaginal microbiome and ≥8.5% of the endometrial microbiome.
Women in the high L/low PB group had the highest pregnancy rate, while those in the low L/high PB group had the lowest.
How might the reproductive tract microbiome affect embryo implantation?
The researchers noted that microbiome changes may affect pregnancy outcomes through the following pathways: Endometrial receptivity: Lactobacillus helps maintain a healthy immune microenvironment that supports implantation, while pathogenic bacteria may trigger inflammation and disrupt implantation. Local immune tolerance: The endometrial microbiome influences maternal immune acceptance of the embryo. Excess pathogenic bacteria may cause the immune system to treat the embryo as foreign, increasing miscarriage risk. Suppression of harmful bacteria: Lactobacillus produces lactic acid, maintaining an acidic reproductive tract environment and reducing pathogen invasion. Growth of pathogenic bacteria may disrupt this balance.
Significance: Could adjusting the microbiome improve pregnancy rates?
The study further supports the key role of Lactobacillus in reproductive health, but the researchers emphasized the need for more research to: Examine the specific effects of different Lactobacillus species, such as Lactobacillus iners, on reproductive health. Study how external interventions, such as probiotic supplements, lactoferrin or antibiotics, might optimize the microbiome and improve IVF success rates.
The team noted that probiotics, dietary changes or microbiome interventions may eventually help optimize the reproductive tract microbiome, improve pregnancy rates and offer new possibilities for patients with infertility.
News | Does the Reproductive Tract Microbiome Affect IVF Success? Study Highlights the Key Role of Lactobacillus
News | Does the reproductive tract microbiome affect IVF success? Study highlights the key role of Lactobacillus
The human microbiome affects not only gut health but may also have far-reaching effects on fertility. A recent study found that the composition of the female reproductive tract microbiome may directly affect the success of assisted reproductive technology (ART), particularly pregnancy outcomes after in vitro fertilization (IVF).
The study was conducted by Miyagi, Mekaru, Tanaka and colleagues and published in JBRA Assisted Reproduction. It found that a reproductive tract microbiome with a high proportion of Lactobacillus was associated with higher pregnancy rates, while overgrowth of certain pathogenic bacteria may reduce the likelihood of pregnancy.
Lactobacillus and reproductive health: Why does microbial balance matter?
The female reproductive tract microbiome is usually dominated by Lactobacillus. These bacteria help maintain an acidic vaginal environment and inhibit harmful bacteria, and may also improve endometrial receptivity. However, when Lactobacillus levels fall and pathogenic bacteria such as **Gardnerella vaginalis, Enterococcus, Streptococcus and Staphylococcus** increase, embryo implantation may be affected and early miscarriage may even occur.
Study background:
The team analyzed 35 women undergoing ART. Next-generation sequencing (NGS) was used to assess their vaginal and endometrial microbiomes and examine how the proportions of Lactobacillus and pathogenic bacteria affected pregnancy outcomes.
All participants received high-quality embryo transfers (ET), and all had an endometrial thickness of at least 8.0 mm, helping ensure that outcomes were influenced as much as possible by microbiome factors rather than embryo quality or uterine conditions.
Participants were divided into four groups according to high or low levels of **Lactobacillus (L) and pathogenic bacteria (PB)**:
High L/low PB (Lactobacillus-dominant, fewer pathogenic bacteria)
High L/high PB (high levels of both Lactobacillus and pathogenic bacteria)
Low L/low PB (lower Lactobacillus, fewer pathogenic bacteria)
Low L/high PB (lower Lactobacillus, more pathogenic bacteria)
Results: Higher pregnancy rates in Lactobacillus-dominant groups
Among 34 embryo transfers, 21 resulted in pregnancy; 17 led to delivery and 4 ended in early miscarriage.
Women who became pregnant had Lactobacillus-dominant vaginal and endometrial microbiomes, while pathogenic bacteria predominated among those who did not become pregnant.
Comparison of microbiome composition showed that:
Pregnancy rates increased significantly when Lactobacillus accounted for ≥46% of the vaginal microbiome and ≥55% of the endometrial microbiome.
Conversely, pregnancy rates fell significantly when pathogenic bacteria accounted for ≥18.7% of the vaginal microbiome and ≥8.5% of the endometrial microbiome.
Women in the high L/low PB group had the highest pregnancy rate, while those in the low L/high PB group had the lowest.
How might the reproductive tract microbiome affect embryo implantation?
The researchers noted that microbiome changes may affect pregnancy outcomes through the following pathways:
Endometrial receptivity: Lactobacillus helps maintain a healthy immune microenvironment that supports implantation, while pathogenic bacteria may trigger inflammation and disrupt implantation.
Local immune tolerance: The endometrial microbiome influences maternal immune acceptance of the embryo. Excess pathogenic bacteria may cause the immune system to treat the embryo as foreign, increasing miscarriage risk.
Suppression of harmful bacteria: Lactobacillus produces lactic acid, maintaining an acidic reproductive tract environment and reducing pathogen invasion. Growth of pathogenic bacteria may disrupt this balance.
Significance: Could adjusting the microbiome improve pregnancy rates?
The study further supports the key role of Lactobacillus in reproductive health, but the researchers emphasized the need for more research to:
Examine the specific effects of different Lactobacillus species, such as Lactobacillus iners, on reproductive health.
Study how external interventions, such as probiotic supplements, lactoferrin or antibiotics, might optimize the microbiome and improve IVF success rates.
The team noted that probiotics, dietary changes or microbiome interventions may eventually help optimize the reproductive tract microbiome, improve pregnancy rates and offer new possibilities for patients with infertility.
Story source:
Collected online