How much does your microbiome really affect your chances of getting pregnant—or IVF success?
In this expert webinar, Angela Heap, Fertility Nutritionist (17+ years clinical experience) explains the critical role of the microbiome in fertility, from the gut to the uterus and even the semen. The session explores how bacterial balance, inflammation, and immune responses can influence conception, implantation, and pregnancy outcomes.
Hosted by Jessica Bourke – Founder of The Fertility Detective, with 20+ years supporting people through fertility struggles and pregnancy loss
This is an essential watch for anyone experiencing unexplained infertility, recurrent miscarriage, implantation failure, or preparing for IVF.
The microbiome is the ecosystem of the body, made up of trillions of bacteria. We have more bacteria in our body than human cells. These bacteria exist in different areas, including the gut, vagina, uterus, and semen, and they interact as part of a connected system.
When this ecosystem is balanced, it supports health. When it becomes imbalanced (dysbiosis), it can lead to inflammation, which affects the immune system. This is particularly important for fertility, as inflammation and immune responses can interfere with conception and implantation.
We are looking at multiple microbiomes in fertility:
Gut microbiome
Vaginal microbiome
Uterine microbiome
Semen microbiome
Each plays a role in reproductive health, and all are interconnected.
Modern diets and lifestyles have significantly altered the microbiome compared to our ancestors, who had a more varied and fiber-rich diet.
Key factors that impact the microbiome include:
Low fiber intake
Lack of dietary diversity
Ultra-processed foods
Frequent antibiotic use
A healthy microbiome depends on:
A varied, plant-rich diet
Adequate fiber intake
Supporting beneficial bacteria through nutrition
Introducing fiber should be done gradually, as the body needs time to adapt. Rapid changes can cause digestive discomfort, especially if beneficial bacteria are depleted.
Historically, the uterus was believed to be sterile. Research now shows that it has its own microbiome, which plays a role in implantation.
The uterine microbiome is particularly important because:
The immune system behaves differently in the uterus
It must allow implantation while maintaining protection
The semen microbiome is also critical. Semen contains bacteria, not just sperm. These bacteria are introduced into the female reproductive system and can influence the uterine environment.
An imbalance in the semen microbiome can:
Trigger immune responses
Affect implantation
Contribute to DNA fragmentation
This highlights the importance of assessing both partners, not just the female.
Microbiome testing is widely accessible and can often be done at home using test kits sent to a laboratory.
Options include:
Vaginal microbiome testing
Uterine microbiome testing
Semen microbiome testing
Next-generation sequencing (NGS) testing
NGS testing provides a broader view of bacterial species, which is important because we are still learning about many of them.
Timing is crucial:
Results may take 4–5 weeks
Treatment may require additional months
Patients should factor this into their fertility treatment timeline.
Microbiome imbalance can affect many patients, particularly those with:
Unexplained infertility
Recurrent implantation failure
Recurrent miscarriage
Endometriosis or PCOS
Autoimmune conditions
Chronic medication use
Immune-modulating treatments, such as steroids, may suppress symptoms without addressing underlying causes like dysbiosis.
An inflamed uterine lining may indicate chronic endometritis, which can result from retained tissue, scarring, or infection.
Recommendations include:
Further investigation (e.g., biopsy or microbiome testing)
Identifying specific bacteria involved
Avoiding overly aggressive antimicrobial treatment initially
Using targeted probiotics, including vaginal application
Treatment should be personalised and guided by a practitioner.
Each case is individual. If significant improvements have been made, it may be appropriate to pause treatment and allow the body to stabilise.
However, partner factors should also be considered, as reinfection or imbalance may occur through sexual activity.
Yes, especially after repeated miscarriage or surgical procedures.
Miscarriage can:
Increase inflammation
Alter the microbiome
Leave retained tissue, which may affect future implantation
Testing can help identify whether further treatment is needed before trying again.
These are invasive tests (biopsies), so they should not be repeated excessively.
Consider:
Allowing time for healing
Using less invasive microbiome testing where possible
Avoiding unnecessary repeated procedures that may affect the uterine lining
Yes. Vaginal dysbiosis can:
Alter pH levels
Increase harmful bacteria
Impact the uterine environment
Factors that disrupt the microbiome include:
Antibiotics
Diet
Sexual activity
In some cases, temporarily avoiding intercourse or using barrier methods may support recovery.
Yes. Miscarriage can significantly alter the microbiome and increase inflammation.
It is important to:
Ensure no retained tissue remains
Allow time for recovery
Consider microbiome testing before attempting conception again
It is best to address microbiome issues before pregnancy.
During pregnancy:
Treatment options are more limited
Invasive treatments should be avoided
Careful monitoring may be required
In some cases, antibiotics may be used under medical supervision.
The ERA test assesses the implantation window, while microbiome testing evaluates bacterial balance.
ERA may be helpful in some cases, but:
Results may vary cycle to cycle
Evidence is mixed
Microbiome balance is considered a more fundamental factor for implantation.
MCAS involves heightened immune responses and inflammation.
This may:
Affect implantation
Create an unfavorable environment for pregnancy
Management requires:
Identifying triggers
Working with a specialist
Addressing underlying causes
