Had a Failed Embryo Transfer Despite a Perfect Cycle?
Your embryo looked perfect. Your lining measured beautifully. Your hormone levels were within normal range. And still…You experienced a failed embryo transfer.
If this sounds familiar, please know that you’re not alone, and you’re not broken.
As a fertility dietitian, I meet many women who feel blindsided by a failed embryo transfer after everything looks ideal. What often gets overlooked? The health of your reproductive tract microbiome.
In this blog, we explore:
- How the microbiome balance affects implantation outcomes
- What the latest research says about failed embryo transfers
- Practical ways to assess and improve your internal environment
1. Why Microbiome Health Matters After a Failed Embryo Transfer
The vaginal, cervical, and uterine environments play a critical role in embryo implantation. Studies now confirm that a Lactobacillus-dominant microbiome is associated with higher pregnancy rates, while dysbiosis—an imbalance between beneficial and harmful bacteria—is linked to failed embryo transfer.
A 2024 study showed that women with a Lactobacillus-rich microbiome had over 70% implantation success, compared to less than 40% in those with dysbiosis (Podzolkova et al., 2024).
Additionally, women with recurrent implantation failure (RIF) had:
- Reduced Lactobacillus level
- Higher levels of Gardnerella, Acinetobacter, and Ureaplasma parvum
- Decreased expression of endometrial receptivity markers (Zhang et al., 2024)
Action Step:
Consult with your fertility specialist about whether endometrial microbiome testing could help uncover hidden causes behind your failed embryo transfer.
2. Specific Bacteria Can Predict a Failed Embryo Transfer
Cutting-edge studies show that certain cervical and vaginal bacteria are strong predictors of failed embryo transfer, even before IVF begins.
A 2025 study identified Halomonas, Klebsiella, and Veillonella as significantly more common in women who didn’t achieve pregnancy. These bacterial profiles contributed to the development of a predictive model for failed implantation (Wu et al., 2025).
Another study reported that a vaginal microbiome containing just 0.5% Ureaplasma parvum was linked to a 75% lower implantation rate (Depenbusch et al., 2024).
These harmful bacteria can:
- Disrupt cervical mucus and pH
- Trigger immune responses
- Allow infections to reach the uterine lining
Action Step:
If you’ve had more than one failed embryo transfer, ask your fertility team about endometrial or vaginal microbiome tests.
3. Personalised Treatments Can Prevent Another Failed Embryo Transfer
The silver lining? Reproductive microbiome imbalances are often correctable, and doing so can significantly improve your IVF outcomes.
In a study, women who received embryo transfer plans tailored to their microbiome and implantation window had over 70% success rates, versus <40% with standard protocols (Podzolkova et al., 2024).
In another study involving nearly 400 women with recurrent implantation failure, the most successful strategy involved combining vaginal probiotics with antibiotics, restoring a healthy Lactobacillus-dominant microbiome in 78.6% of cases (Kadogami et al., 2020).
By contrast:
- Oral probiotics alone = ~30% success
- Oral + vaginal probiotics = 78.6% success
Action Step:
Work with a fertility dietitian to build a plan that includes:
- An anti-inflammatory eating plan to support a healthy endometrial lining
- Targeted probiotic support (not all probiotics are effective for the reproductive tract!)
- Gentle lifestyle strategies to lower inflammation and enhance microbiome balance
Bottom Line
If your IVF cycles are failing despite textbook-perfect embryos and lining, it may be time to explore what’s happening behind the scenes:
- Check your endometrial and vaginal microbiome: A Lactobacillus-dominant vaginal and endometrial microbiome is crucial for successful implantation.
- Watch for red flags: Pathogenic bacteria like Ureaplasma, Klebsiella, or Gardnerella can silently reduce your chances of pregnancy.
- Treat early and specifically: Personalised protocols combining antibiotics and vaginal probiotics show the best outcomes for restoring microbiome balance.
