A new study from UTHealth Houston found that the common sexually transmitted infection, Mycoplasma genitalium, also known as MGen, does not appear to increase the risk of recurrent preterm birth.
The findings were published in The American Journal of Obstetrics and Gynecology.
Mycoplasma genitalium is a common sexually transmitted disease caused by a tiny bacteria that can infect the urethra or reproductive tract. Most people with the condition have no symptoms, but when it does cause symptoms, it can lead to irritation or inflammation that needs treatment.
Preterm birth is defined as delivery before 37 weeks and is a leading cause of infant illness and death. Earlier research suggested that certain Mycoplasma species might contribute to preterm labor, but those studies were limited.
"These findings provide important new insight into the role of Mycoplasma genitalium in pregnancy," said Irene Stafford , MD, MPH, first author of the study and assistant professor in the Department of Obstetrics, Gynecology and Reproductive Sciences with McGovern Medical School at UTHealth Houston. "Given its links to HIV acquisition and growing antimicrobial resistance, continued study of this emerging infection remains an important public health priority."
Mycoplasmas are a group of tiny bacteria that can live in the genital tract. Unlike most bacteria, they don't have a cell wall, which makes them harder to detect and treat. Because of mycoplasma genitalium's link to inflammation, researchers questioned whether mycoplasma genitalium might play a role in pregnancy complications, including recurrent preterm birth.
To better understand the connection, researchers conducted a first-of-its-kind prospective study in nearly 500 pregnant individuals with a history of preterm birth or related complications. The patients were enrolled between July 2023 and December 2025. Participants were tested early in pregnancy for Mycoplasma genitalium using an FDA?cleared vaginal swab test.
The study found that 12% of participants tested positive for Mycoplasma genitalium. The infection was significantly more common among those who had experienced a prior preterm birth. However, Mycoplasma genitalium did not increase the risk of having another spontaneous preterm birth or a second?trimester loss caused by cervical insufficiency, which the study also explored.
The findings suggest that while Mycoplasma genitalium may be associated with past pregnancy complications, it does not appear to drive recurrent preterm birth in subsequent pregnancies. Researchers note that Mycoplasma genitalium may pose more risk during a first-time or incident infection, when the body has not yet developed an immune response.
"This study provides important clarity for patients and clinicians," said Stafford, who is a maternal-fetal medicine physician. "For individuals already at high risk of preterm birth, Mycoplasma genitalium infection alone does not seem to increase the likelihood of another early delivery."
Researchers emphasize that more studies are needed, as preterm birth is complex and influenced by many factors. Still, these results offer reassurance and help guide future screening and treatment decisions.
Other UTHealth Houston researchers on the study include Sean Blackwell, MD; Han-Yang Chen, PhD; Sahana Kodali, BS; and Mason Collie, BS.
Additional contributors are Erik Munson, PhD, with Marquette University, and Damon Getman, PhD, with Hologic Inc.
