Lyme disease and your pregnancy: Why avoiding tick bites could protect your unborn child

As many regions of Canada experience a population explosion of ticks and Lyme disease case counts soar, researchers are calling for more investigation into pregnant women passing the potentially deadly infection on to their unborn children. 

It’s the subject of two papers released in early 2026. One is a case study in which a mother possibly transmitted the pathogen that causes Lyme disease to her daughter in utero, published in the journal MDPI in February. The other is a review of the evidence of mother-to-fetus transmission, published in the journal Frontiers in April. 

Researchers have been aware since the mid-1980s of possible cases in which pregnant women have passed Borrelia burgdorferi, the bacterium that causes Lyme disease, on to their fetuses. Forty years later, however, the problem remains “understudied and poorly defined,” the authors of the Frontiers review state.

Dr. Vett Lloyd, a professor of microbiology at New Brunswick’s Mount Allison University who co-authored the case study in MDPI, agrees there are many questions researchers have yet to answer. Lloyd, a member of the Canadian Lyme Disease Foundation’s board of directors, outlined some of those questions in a June interview.

“How often does infection pass from mother to fetus and under what conditions? What are the range of effects on the fetus and/or infant? What are the long term effects on the child and how should infection be determined and managed?” Lloyd says.

“At this point we just don’t know enough for health-care providers to provide guidance to pregnant individuals or those who may become pregnant. And that’s a problem,” she says. 

That problem is getting more serious with each passing year as climate change fuels the spread of ticks in Canada, and Lyme disease becomes more prevalent. Health Canada says 28,033 people have been diagnosed with Lyme disease since 2009, the year the provinces began reporting cases. But according to at least one estimate, the actual number is more than 13 times higher. That makes it all the more urgent that women take precautions to protect themselves and their unborn children from the country’s most common vector-borne infection. 

Moreover, Lloyd and the other authors of the case study published in MDPI warn that transmission of the pathogen from mother to fetus can lead to “adverse pregnancy outcomes, including neonatal death.”

“This topic deserves urgent attention since confirmation of transmission from mother to child elevates the complexity of [Lyme disease] diagnosis and treatment,” the article states.

From mother to daughter 

“In this report we present a case of possible vertical transmission of B. burgdorferi, detected using advanced methods including indirect immunofluorescence, PCR, and bacterial culture, confirmed by different laboratories.”

The case study tells the story of a 39-year-old woman from southern Ontario – a high-risk region for Lyme disease – and her daughter. At age 32, the woman fell ill in the first trimester of her pregnancy in Kenya. Her doctors suspected malaria but that was ruled out. Initial blood tests for Lyme disease were inconclusive. It was only years later after suffering “ongoing and unrelenting fatigue and migratory pain,” along with other symptoms, that she was accurately diagnosed and treated with antibiotics.

Since her birth, the woman’s daughter has also suffered from a range of health problems. Soon after she was born she was diagnosed with “hyperbilirubinemia and was hospitalized overnight for phototherapy,” the authors state.

“At 11 weeks of age, she developed a high fever and was assessed in the Emergency Department, although routine testing did not identify a cause. Early childhood was characterized by cyclical fevers and cyclical vomiting. At age four, symptoms of unexplained pain and hypersensitivity to light and sound developed,” the article says. 

At age five, she also developed a series of rashes. Standard testing for Lyme disease came back negative. However, eventually, a physician in the U.S. diagnosed her accurately and she was treated with antibiotics.

With the mother’s consent, the researchers studied her medical records, as well as archived bodily fluid and tissue samples taken at the time, along with those of her child. Using advanced diagnostic techniques they found the same strain of Borrelia burgdorferi in the woman’s placenta that infected her daughter. 

Lloyd says the case study is important partly because it uncovered evidence of congenital transmission missed by the standard blood tests still in use in this country, which can only detect the immune response to the bacteria, not the pathogen itself.

“This means that there will be more individuals infected than we know about … Some of these individuals will be individuals who are or who become pregnant,” she says.

But health professionals still can’t come to a consensus about screening pregnant women for Lyme disease, Lloyd says. 

“Some experts recommend routine pre- and  perinatal screening for Lyme disease in endemic areas. Others disagree.”

Hope and healing

The expert review published in Frontiers recommends a comprehensive push for more research on congenital transmission of Lyme disease, as well as better surveillance, diagnosis and prevention.

“As the prevalence of [Lyme disease] continues to escalate globally, the identification of accurate diagnostics and effective clinical management for both mother and baby must be prioritized with a coordinated multi-disciplinary, multi-institutional research and policy response,” the paper reads. 

“Scientific and clinical advances within the field will lead to new avenues for improved surveillance, health care professional education, and evidence-based diagnostic, prevention, and treatment strategies, providing hope and healing for impacted women and their children.”

References

Faber S, Mao C, Darling E, Ahern H, Brissette C, Gardner TD, Weis JJ, Bergström S, Breitschwerdt EB, Coyne CB, et al. 2026. Perinatal transmission of Borrelia burgdorferi: advancing scientific and clinical understanding of Lyme disease in pregnancy. Frontiers in Medicine. 13. doi:https://doi.org/10.3389/fmed.2026.1794120.

Bemis LT, Golovchenko M, Ericson ME, Haque MdH, Lloyd V, Rudenko N. 2026. Advanced Molecular and Microscopic Diagnostics Suggest Congenital Borrelia Transmission: A Case Report. Microorganisms. 14(2):406. doi:https://doi.org/10.3390/microorganisms14020406.