Lyme’s effect on pregnant women and their babies has largely been ignored by researchers, report warns

Pregnant women’s risk of contracting Lyme disease, and the possible effect on their unborn babies, is an area that needs much more study as the threat of tick-borne illnesses sharply increases globally, an American report warns.

“While work has progressed in understanding the disease manifestations and pathogenesis of tick-borne pathogens, pregnancy as a risk factor has largely been ignored,” according to the narrative review, which was released last October by MDPI, a publisher of peer-reviewed, open-access journals. 

“Altered immune system physiology during pregnancy may lead to an increased susceptibility or severity of infectious diseases,” including tick-borne infections like Lyme disease, the authors state. 

The risks Lyme disease poses to pregnant women warrant further study because of the sharply increasing “overlap between human populations and tick habitats,” especially in the world’s fastest growing cities, the review says.

Knowledge of impact on pregnancy very limited

“Unfortunately, studies have reported the presence of pathogens in the ticks and wildlife in urban green spaces globally … Concerningly, over half of the world’s population lives in urban settings with projections estimating that number to grow to 70 per cent by 2050,” the article continues.

Here in Canada, reports such as this one from Ontario have also been warning for years of a rise in populations of disease-causing ticks in urban areas.

In spite of this, the review says, the research community’s body of knowledge concerning tick-borne illness in pregnant women is “very limited.” 

The authors, Michael W. Curtis and Job E.Lopez of Baylor University in Houston, cite two main areas of research into the impact of Lyme disease, which they describe as the “most common tick-borne infection in the United States and Europe,” on pregnant women and their fetuses. 

• Maternal and perinatal adverse outcomes. 
•  The transmission of Lyme disease-causing bacteria from mother to offspring. 

Indirect evidence of harm to offspring 

Much of this research began more than 40 years ago, the authors state. 

For example, they point to 19 cases of pregnant women with Lyme reported by the U.S. Centers For Disease Control in the early 1980s which resulted in a range of severe outcomes, including the death of the fetus, premature birth and developmental delay, while the other 14 cases “resulted in healthy births.” 

The article says analysis of additional case reports, and subsequent epidemiological studies conducted in the 1980s and 1990s, found little evidence of a significant relationship between Lyme disease in pregnant women and negative effects on their offspring, with some of the results being unclear or ambiguous. 

But more recent studies suggest a relationship could exist. The authors point to a “systematic review” of  “29 case reports or series and 17 epidemiology studies published globally,” which  “investigated the association between Lyme disease and adverse maternal or perinatal outcomes.” 

While there were reports of adverse outcomes in 59 cases, “the authors did not find any difference in the prevalence of adverse pregnancy outcomes between the populations exposed to Lyme disease (defined by the individual authors as gestational LD, history of LD, tick bites, or residence in an endemic area) and the control populations,” the article states. 

But further study did find a possible link, although it was “indirect,” the report says. 

 “When the authors performed a meta-analysis of nine studies that investigated the pregnancy outcomes of treated vs. untreated gestational Lyme disease, they found indirect evidence that Lyme disease-causing (bacterial) infection may cause adverse pregnancy outcomes. The meta-analysis revealed fewer adverse outcomes in the treated pregnant populations compared to the untreated pregnant populations.” 

Patient-centred research at McMaster

The article also cites an “international cross-sectional survey” derived from data gathered by the Midwifery Research Centre at McMaster University in Hamilton, Ont., on perinatal transmission of Lyme, published last year, which included surveys and interviews with online focus groups made up of patients themselves.

Although the authors of the study itself cite limitations in the data, it is an example of the kind of patient-centred research championed by the Canadian Lyme Disease Foundation, including by incoming advisory board Mario Levesque, an associate professor at New Brunswick’s Mount Allison University who has studied Lyme disease and the effects of public policy on its detection and treatment for 20 years.  

The study separated the participants into groups dubbed: 

• Probable Treated for Lyme Disease. 
• Probable Untreated.
• Possible Untreated.
• No Evidence of Lyme Disease.

“The authors found the “No Evidence of Lyme disease” group reported significantly fewer complications compared to the Probable Treated, Probable Untreated, and Possible Untreated Lyme disease groups,” the review says.

“Rash, hypotonia, and respiratory distress were reported in newborns within the first two weeks after birth more frequently in the Probable Untreated group compared to the Probable Treated, Possible Untreated, and No Evidence of Lyme disease groups.” 

Babesia’s effect on mothers, newborns not well-understood

Babesia is another tick-borne illness that largely strikes in the U.S northeast and upper Midwest. 

The U.S. Centers for Disease Control estimates there are anywhere between 1,000 and 3,000 cases annually, but the report says there have been “less than 15 published cases that document disease progression and maternal and fetal outcomes following Babesia infection during pregnancy.”

The review says the infection can be anywhere from asymptomatic, mild to severe and the maternal symptoms can include:

• Fever and fatigue.
• Chills and headache.
• Joint pain and jaundice.
• Weakness and shortness of breath. 
• Cough and respiratory failure.
• Renal failure. 

Although the report says the effects of babesia on mothers and newborns are “not well understood,” and there has been little research done beyond the use of animal models, these studies “demonstrate that Babesia infection can be vertically transmitted from mother to offspring and can severely impact pregnancy.”

Much more research needed

The review says researchers need to do much more work to better understand the risk of tick-borne diseases to pregnant women and their offspring, 

“We need the continued publication of case reports, larger epidemiologic studies, and animal studies using biologically relevant transmission routes in animal models that mimic human disease,” the authors write.

“Case reports are critical for the continued awareness and consideration of tick-borne infections during pregnancy. Large epidemiological studies are necessary to understand the causal link between tick-borne infections and pregnancy outcomes,” the report continues.

”Future large-scale prospective studies are warranted.”