A new study has uncovered significant findings about how Lyme disease can impact the female reproductive system.

While previous research primarily focused on the effects of Borrelia (Lyme) on pregnancy, this study explores how the infection affects the reproductive system in non-pregnant mice.

These findings may offer valuable insights into potential connections with human gynecological disorders.

In a MedRxiv article entitled, Lyme disease increases risk for multiple gynecological conditions, MIT researchers Michal Caspi Tal, PhD, and Paige S. Hansen Colburn teamed up with researchers from the Fred Hutchinson Cancer Center, Nasa Sinnott-Armstrong, PhD, and colleagues.

“This changes how we understand Lyme”

Dr. Tal says, “For years, people have been asking if Lyme disease might cause miscarriage and other pregnancy problems. Our study shows a strong link, and more research is vital. This research changes how we understand Lyme. It’s a much bigger problem than we thought, especially for women.”

Tracking the illness for months, the team demonstrated that Lyme disease can cause prolonged and severe infection in the reproductive organs of female mice.

The study documented infected gynecological tissue, and problems such as enlarged uterus, ovarian cysts, thickening of the vaginal lining and inflammation of the internal and external tissues. Notably, older mice experienced more severe outcomes when infected.

Hansen Colburn says, “Our research both supports previous studies on Lyme in pregnancy and also highlights novel implications for Lyme in women’s health outside of the reproductive lens.”

In addition, using clinical and survey data, the researchers found associations between Lyme disease and an increased risk of endometriosis, dysmenorrhea (menstrual cramps), menorrhagia (heavy periods), miscarriage, uterine polyps, and endometriosis (uterine tissue growing outside the uterus).

Supporting evidence from human data

These findings were corroborated with data from a Finnish database, which showed higher rates of gynecological issues like miscarriage, vulvovaginitis, uterine fibroids, and dysmenorrhea in women with Lyme disease.

Hansen Colburn says, “We still need to learn exactly how the bacteria cause this damage. Is it the bacteria themselves, or is it collateral damage from the body’s immune response?”

It’s known that men and women exhibit different symptoms of Lyme disease. For example, men tend to develop a larger more typical Lyme rash than women. Men are also more likely to have a CDC-positive two-tier test for Lyme. But why?

In order to prevent miscarriage, women’s bodies are designed to alter their hormones and immune response when pregnant. It may be that female hormones or this immune response set women up for chronic Lyme.

Elevated risk

“Lyme disease appears to elevate risk of many gynecological diseases, and we still have a lot to learn about what else might result from Borrelia infection. This is just the beginning,” says Sinnott-Armstrong.

This study emphasizes the importance of:

• tracking gender in Lyme disease studies
• tracking age-related status
• understanding the hormonal phase at the time of infection, during treatment and post-infection (eg. pre & post-pubescent, peri & post-menopausal)
• understanding hormone levels and hormone dysregulation
• tracking reproductive pathologies in both male and female patients with Lyme disease.

Findings from MyLymeData

In 2019, LymeDisease.org published results of a MyLymeData study, Gender Bias in Chronic Lyme Disease, showing that women are at a disadvantage when it comes to Lyme disease. Not just because women’s bodies respond differently to infection, but also because women represent a smaller percentage of participants in acute Lyme disease research.

A follow-up MyLymeData study, Does Biological Sex Matter in Lyme Disease? The Need for Sex-Disaggregated Data in Persistent Illness, published in 2023, found that women encountered lengthier diagnostic delays, grappled with more severe symptoms, and suffered greater functional impairment compared to men.

The MyLymeData authors concluded, “Our results indicate that biological sex should be integrated into Lyme disease research as a distinct variable. Future Lyme disease studies should include sex-based disaggregated data to illuminate differences that may exist between men and women with persistent illness.” (Disaggregated means that you separate out the data from male and female patients, so that you can look for trends in each group.)

Next steps

Today, we owe a huge thank you to the Tal Research Group and the Sinnott-Armstrong lab for demonstrating that Lyme disease increases the risk for gynecological disorders in women.

Dr Tal tells me the next step is to work on treatment protocols. “We’re very interested in the intersection of hormones and immune responses to infection, and we’ll be testing out different treatment protocols for the infection and also modulating the immune response to the infection to try to understand once this gynecological damage has happened, if antibiotic treatment alone be sufficient to reverse it.”

The Tal Research Group at MIT has also found Borrelia bacteria in the male reproductive tract, which is currently being investigated further.

The CDC estimates there are 475,000 annual cases of Lyme disease, however they make no meaningful analysis of sex differences in their list of symptoms or progression of disease.

Furthermore, approximately 5 million women in the U.S. suffer from endometriosis. Perhaps some of them would benefit from exploring a diagnosis and treatment for Lyme disease?

We look forward to the continued MIT research results and further understanding of chronic illness following infection.

LymeSci is written by Lonnie Marcum, a physical therapist and mother of a daughter with Lyme. She served two terms on a subcommittee of the federal Tick-Borne Disease Working Group. Follow her on X: @LonnieRhea   Email her at: lmarcum@lymedisease.org.

Reference

Hansen–Colburn PS, Blacker G, Galloway S, Feng Q, Padmanabham PS, Pisani G, Lee BT, Loeser G, Perez MW, Liu K, Kuan J, Von Saltza E, Strausz S, Mattei L, Nahass GR, Kitjasateanphun A, Potula HS, Shoham MA, Mascetti VL, Gars E, Ollila HM, Bruner-Tran KL, Weissman IL, You S, Pollack B, Griffith L, Sinnott-Armstrong N, Tal MC. (2025). Lyme disease increases risk for multiple gynecological conditions. medRxiv. https://doi.org/10.1101/2025.03.03.25323258.

Acknowledgement

This research was supported, in part, by the Emily and Malcolm Fairbairn donor advised fund.