A Microbiome Link to Infertility

Guest BloggerClinical Corner, Market Trends


In The Handmaid’s Tale, author Margaret Atwood depicts a future where mass infertility leads to draconian fixes. In our non-fiction world of 2017, inability to make a baby occurs but in numbers which won’t yet threaten the survival of humanity. But for couples wanting a child but incapable, the situation can be devastating. The World Health Organisation (WHO) estimates that nearly 50 million couples worldwide are infertile.

Infertility is the inability of a sexually active, non-contracepting couple to achieve pregnancy in one year.

There is a microbe connection, underexplored in the field, which starts with a question:

What causes infertility?

Causes are numerous with men and women sharing the origins.

  • Pathogens such as sexually transmitted diseases (STDs) including Chlamydia and gonorrhea can cause infertility, making prompt treatment vital.
  • Common conditions including bacterial vaginosis (BV) may also lessen fertility.
  • Stress, poor nutrition, obesity, chemical toxins, and excessive alcohol can mimic pathogens in their adverse effects on embryo development.

How does the microbiome fit in with fertility and assisted reproductive technology (ART)?

Researcher Ida Sirota of St. Luke’s-Roosevelt Hospital Center in New York City and two colleagues at the National Institutes of Health published an excellent review of present knowledge in Seminars in Reproductive Medicine: Potential Influence of the Microbiome on Infertility and Assisted Reproductive Technology.

Far beyond the purview of a petri dish, the Human Microbiome Project (HMP) with its advanced genomic sequencing, write the authors, has uncovered much useful data in the last decade:

  • The vagina has less diversity than other sites in the body.
  • Lactobacillus comprises 90 to 95% of the total bacterial count in the reproductive tract.
  • Four species predominate: Lactobacillus crispatus, Lactobacillus iners, Lactobacillus jensenii, and Lactobacillus gasseri.

This “normal” flora promotes a healthy environment for implantation of the embryo by production of:

  • Lactic acid (lowers the vaginal pH and makes it an unfavorable habitat for pathogens).
  • Hydrogen peroxide (live birth rate (LBR) is increased with presence of hydrogen peroxide-producing lactobacilli from the embryo transfer-catheter tip in ART).
  • Bacteriocins
  • Antibiotic toxic hydroxyl radicals
  • Probiotics

Of all these, both lactic acid and hydrogen peroxide from lactobacilli play a pivotal role in favor of successful implantation and pregnancy. Indeed, studies show that up to 40% of patients undergoing IVF cycles have abnormal reproductive tract microbiota.

A recent ART study with 30 patients sought to correlate patterns of vaginal microbiota during in vitro cycles using modern 16S sequencing method. The results showed that the most successful outcomes were with a vaginal microbiome composed solely of lactobacilli.

Other exciting findings discussed in the review:

“colonizing the transfer-catheter tip with Lactobacillus crispatus at the time of embryo transfer may increase the rates of implantation and live birth rate while decreasing the rate of infection.”

In addition, a progesterone-resistant endometrium may increase the risk of an abnormal vaginal microbiome. This resistance might increase sensitivity to inflammation, even in subsequent generations not exposed to the toxicants. The embryo may struggle to implant under these conditions.

It is complicated. But a  healthy microbiome in the reproductive tract is essential to provide the best environment for a new baby. As science leads to more discovery, expect probiotics along with a healthy diet to play a bigger part in confronting infertility.