Ureaplasma is a type of bacteria that naturally lives in the urinary and genital tracts of many adults. Around 21% of healthy, sexually active people carry it without any symptoms. It belongs to a unique class of bacteria that evolved to lose their cell walls, which makes them invisible on standard lab tests and resistant to some common antibiotics. Most of the time, ureaplasma causes no problems at all, but when it overgrows or spreads to the wrong place, it can trigger infections in the urinary tract, reproductive organs, and, during pregnancy, pose risks to both mother and baby.
A Bacterium Without a Cell Wall
Ureaplasma evolved from the same bacterial lineage as other common bacteria, but over time it shed its protective outer layer, called a cell wall. This makes it fundamentally different from most bacteria your immune system encounters. Typical bacteria have a rigid outer shell made of a substance called peptidoglycan, which the immune system recognizes and attacks. Ureaplasma lacks this entirely, meaning the usual immune alarm signals that other bacteria trigger don’t fire the same way. This is also why antibiotics that work by breaking down bacterial cell walls (like penicillin and amoxicillin) have no effect on ureaplasma.
There are two species: Ureaplasma parvum and Ureaplasma urealyticum. The two can only be distinguished through molecular testing like PCR, so in most clinical settings they’re simply grouped together as “Ureaplasma species.” Parvum is more commonly detected in samples, but urealyticum appears to be the more problematic of the two, particularly when it comes to urethritis in men.
How Common It Is
Ureaplasma is one of the most frequently detected organisms in the genital tract. Studies find it in roughly 14% of completely asymptomatic people who have no reason to suspect an infection. In sexually active populations more broadly, prevalence estimates reach 21% or higher. It spreads primarily through sexual contact, though it can also pass from mother to baby during pregnancy or delivery. Having multiple sexual partners increases the likelihood of carrying it, but many people acquire it from a single partner and carry it harmlessly for years.
Symptoms in Women
When ureaplasma overgrows in the vaginal or urinary tract, it often presents as bacterial vaginosis. Symptoms include a thin gray, white, or greenish vaginal discharge, a persistent “fishy” odor, vaginal itchiness and redness, burning during urination, and a feeling of pressure or heaviness in the pelvis. These symptoms tend to be mild but can be stubborn, often recurring after treatment or lingering longer than expected.
Ureaplasma can also contribute to urinary tract infections and, less commonly, pelvic inflammatory disease. In many women, though, the bacteria sit quietly in the genital tract without causing any noticeable symptoms. This is why a positive test result alone doesn’t always mean treatment is needed.
Symptoms in Men
In men, the primary concern is nongonococcal urethritis, an inflammation of the urethra not caused by gonorrhea. Symptoms include a burning sensation during urination, a clear or slightly cloudy discharge from the penis, and irritation at the urethral opening. Ureaplasma urealyticum specifically has been linked to urethritis more consistently than its sibling species. As with women, many men carry the bacteria with no symptoms whatsoever.
Effects on Fertility
Ureaplasma infection in the male reproductive tract can trigger inflammation and oxidative stress, leading to increased sperm DNA fragmentation and reduced sperm maturity. In practical terms, this means the sperm may look normal under a microscope but carry damaged genetic material that reduces the chances of successful fertilization. Infection can also prompt the immune system to produce antibodies that attack sperm directly, further impairing their function and motility.
In women, ureaplasma has been associated with conditions that affect the uterine lining and fallopian tubes, both of which matter for implantation and early pregnancy. For couples struggling with unexplained infertility, testing for ureaplasma is sometimes part of the workup, particularly before IVF cycles, where sperm quality and uterine environment are closely monitored.
Risks During Pregnancy
Pregnancy is where ureaplasma shifts from a nuisance to a genuine concern. The bacteria can pass from mother to fetus either in the uterus or during labor. Once present, ureaplasma activates the immune system in ways that increase the production of inflammatory molecules, which can trigger uterine contractions, cervical dilation, and premature rupture of the membranes (when the water breaks too early).
In one study of preterm births, ureaplasma was detected in 52% of cases. The infection was statistically linked to premature membrane rupture, placental inflammation, and newborn respiratory distress syndrome. Nearly half (47%) of the newborns in that study developed respiratory distress. The connection between ureaplasma and these pregnancy complications held regardless of other infection markers, suggesting the bacteria itself plays a direct role rather than simply being a bystander.
Beyond preterm birth, ureaplasma during pregnancy has been associated with infection of the uterine lining after delivery (postpartum endometritis) and inflammation of the umbilical cord. These risks make screening and treatment during pregnancy more important than in non-pregnant adults, where the bacteria often coexist peacefully.
How Ureaplasma Is Detected
Standard bacterial cultures frequently miss ureaplasma because the organism grows slowly and requires specialized growth media. In one comparison study, culture identified only 5 positive results from 50 samples, while PCR testing (which detects bacterial DNA directly) found the organism in 12 of those same samples. PCR is faster and significantly more sensitive, making it the preferred diagnostic method. If you’ve been tested through a standard urine culture or vaginal swab and the result was negative, that doesn’t necessarily rule out ureaplasma. You may need to specifically request PCR-based testing.
Testing is typically recommended when you have persistent urethritis or vaginal symptoms that don’t respond to initial treatment, unexplained infertility, recurrent pregnancy losses, or a history of preterm birth. Routine screening of people without symptoms is generally not recommended, since so many healthy adults carry the bacteria without consequence.
Treatment and Antibiotic Resistance
Because ureaplasma lacks a cell wall, the standard antibiotics many people are familiar with simply don’t work. Treatment relies on antibiotics that target bacterial protein production instead. Doxycycline is typically the first-line option, with resistance rates around 10% in recent studies. Azithromycin is an alternative, but resistance is climbing: rates have risen from about 17% to 28% in recent years, a statistically significant upward trend.
Treatment courses are generally short, ranging from one to two weeks depending on the medication and the severity of symptoms. Symptoms that are mild but persistent may require a second course or a switch to a different antibiotic if the first doesn’t clear the infection. Given rising resistance, some clinicians now order sensitivity testing alongside PCR to determine which antibiotics a specific strain will respond to, rather than prescribing empirically.
Should Sexual Partners Be Treated?
This is a gray area. Ureaplasma passes easily between sexual partners, and reinfection after treatment is common if only one partner is treated. Research on closely related genital bacteria shows high concordance rates between partners, meaning if one person carries it, the other very likely does too. However, no studies have definitively proven that treating both partners at the same time reduces reinfection rates. In practice, many clinicians recommend testing the partner and treating them if they test positive, particularly when the original patient has recurrent symptoms after completing a course of antibiotics.
Using barrier protection during treatment and until both partners test negative can reduce the chance of passing the bacteria back and forth. For couples dealing with fertility issues or pregnancy complications linked to ureaplasma, concurrent treatment of both partners is more common.