As an endocrinologist, much of my daily work focuses on hormonal health, metabolic balance, and conditions such as PCOS that often intersect with fertility. While I don’t perform IVF myself, I frequently refer patients to reproductive specialists. In that context, I’m always attentive to emerging evidence that may influence outcomes for the women I care for.
One area gaining attention is the vaginal microbiota—the community of bacteria that inhabit the vaginal environment. Traditionally, our focus in fertility has been on hormones, ovulation, and embryo quality. Yet research is showing that microbial balance may also play a decisive role in IVF success.
Why the Microbiome Matters
- Protective role of Lactobacillus: In a healthy state, Lactobacillus species dominate, producing lactic acid that maintains a protective acidic environment.
- Dysbiosis and risk: When this balance is disrupted—known as dysbiosis—pathogenic bacteria can proliferate, increasing inflammation and potentially impairing implantation.
- Clinical relevance: For women undergoing IVF, the state of the vaginal microbiota at the time of embryo transfer may influence whether pregnancy is achieved and sustained.
Study Results
A recent 2025 study divided women undergoing IVF into two groups based on their vaginal microbiota profile:
- Group A (Lactobacillus‑dominant microbiota)
- Clinical pregnancy rate: 53%
- Implantation success: 70%
- Group B (non‑Lactobacillus or dysbiotic microbiota)
- Clinical pregnancy rate: 25%
- Implantation success: 42%
These findings are striking. Women with a Lactobacillus-rich microbiome had more than double the pregnancy rate compared to those with dysbiosis.
Endocrinologist’s Perspective
For patients I see in clinic—many of whom are navigating PCOS, thyroid disorders, or metabolic conditions—the journey to IVF is often complex. While microbiome testing is not yet routine, this research highlights several important points:
- Holistic fertility care: Hormones, metabolic health, and microbial balance are interconnected. Supporting one area may benefit the others.
- Referral conversations: When I refer patients to IVF specialists, I now consider whether microbiome health could be part of the discussion.
- Practical reassurance: Patients should know that while microbiota is important, it is one of several factors influencing IVF success. Age, embryo quality, and uterine health remain central.
Takeaway
The vaginal microbiota is emerging as a determinant of IVF success. For endocrinologists, this research is a reminder that fertility care extends beyond hormones alone. While interventions such as probiotics or antimicrobial therapy require further validation, awareness of microbial health can enrich the conversations we have with patients preparing for IVF.
References
- Haahr T, et al. The impact of vaginal microbiota on IVF success. Reproductive BioMedicine Online. 2025. ScienceDirect abstract
- Moreno I, et al. Endometrial microbiota and implantation. American Journal of Obstetrics & Gynecology. 2023.
- Koedooder R, et al. Vaginal microbiome screening before IVF. Microbiology Spectrum. 2024.