Chlamydia often causes no noticeable symptoms at all, which is exactly what makes it dangerous. At least 70% of women and 50% of men with genital chlamydia have no symptoms at the time of diagnosis. Left untreated, the infection can silently damage reproductive organs, increase the risk of ectopic pregnancy, and pass to newborns during delivery. The effects range from mild discomfort to permanent infertility, depending on how long the infection goes undetected.
Why Most People Don’t Notice It
Chlamydia earns its reputation as a “silent” infection because the majority of cases produce no obvious signs. When symptoms do appear, they typically show up one to three weeks after exposure, though some people don’t develop symptoms for months. In women, the most common signs are unusual vaginal discharge, burning during urination, and bleeding between periods. Men may notice a watery or milky discharge from the penis, burning when urinating, or mild irritation at the tip of the penis.
Because so many infections fly under the radar, routine screening is the only reliable way to catch chlamydia early. The CDC recommends annual screening for all sexually active women under 25, and for older women with risk factors like a new partner or multiple partners. Men who have sex with men should be screened at least annually, and every three to six months if they have multiple partners or are on PrEP.
Effects on the Reproductive System in Women
The most serious consequence of untreated chlamydia in women is pelvic inflammatory disease, an infection that spreads from the cervix into the uterus, fallopian tubes, and surrounding tissue. PID can cause deep pelvic pain, fever, and heavy or irregular bleeding, but it can also develop with symptoms subtle enough to go unnoticed. The real damage happens internally: the infection triggers inflammation that produces scar tissue in the fallopian tubes.
That scarring has lasting consequences. Up to 1 in 10 women who develop PID are eventually diagnosed with infertility because scar tissue blocks the fallopian tubes and prevents eggs from reaching the uterus. A large prospective study published in The Lancet Regional Health followed women from 2008 to 2022 and found that those who tested positive for chlamydia had 2.75 times the risk of tubal factor infertility compared to women who tested negative.
Ectopic pregnancy, where a fertilized egg implants in a fallopian tube instead of the uterus, is another serious risk. The same study found women with a chlamydia history had roughly 1.8 times the risk of ectopic pregnancy. Ectopic pregnancies are medical emergencies that can cause life-threatening internal bleeding and always result in pregnancy loss. Even a single chlamydia infection that resolves on its own or goes briefly untreated can leave enough tubal scarring to raise these risks, and the overall risk of PID was about 60% higher in women with prior chlamydia infections.
Effects on Men
In men, untreated chlamydia most commonly spreads to the epididymis, the coiled tube behind each testicle that stores and carries sperm. This condition, called epididymitis, causes pain and swelling on one side of the scrotum, tenderness along the spermatic cord, and sometimes fluid buildup around the testicle. The pain typically comes on gradually rather than all at once.
If epididymitis goes untreated or recurs, it can lead to chronic testicular pain and, in some cases, reduced fertility. Scarring in the epididymis can block the passage of sperm, though this outcome is less common than the fertility complications women face. Men can also develop reactive arthritis after a chlamydia infection, a condition where the immune system’s response to the bacteria triggers joint pain, eye inflammation, and urinary symptoms weeks after the original infection.
Rectal and Throat Infections
Chlamydia doesn’t only infect the genitals. Rectal infections, spread through receptive anal sex, can cause anal pain, discharge, and bleeding. These symptoms are sometimes mistaken for hemorrhoids or other digestive issues, which delays diagnosis. Throat infections from oral sex are also possible but almost always produce no symptoms, making them easy to miss entirely without targeted testing.
Rectal and throat infections matter because they serve as hidden reservoirs. Someone treated for genital chlamydia can remain infected at another site and continue transmitting the bacteria. This is one reason screening guidelines now recommend that clinicians consider rectal testing based on a patient’s sexual history.
Risks During Pregnancy
Chlamydia during pregnancy creates risks for both the mother and the baby. Maternal infection has been linked to premature rupture of membranes, preterm labor, and low birth weight. The most direct threat to the baby comes during vaginal delivery, when the infection can pass from mother to child. Without treatment, vertical transmission rates are estimated at 50 to 70%.
Newborns exposed to chlamydia during birth face two main complications. Between 30 and 50% develop conjunctivitis, an eye infection that appears within the first two weeks of life and can damage the cornea if untreated. Another 10 to 20% develop chlamydial pneumonia, which typically emerges between one and three months after birth with a distinctive staccato cough, rapid breathing, and no fever. Both conditions are treatable with antibiotics, but prevention through maternal screening is far preferable.
Current guidelines recommend screening all pregnant women under 25, with retesting during the third trimester. Pregnant women who test positive should have a follow-up test four weeks after completing treatment to confirm the infection has cleared.
Treatment and Reinfection
Chlamydia is curable with a short course of antibiotics, and most uncomplicated infections clear completely with proper treatment. The catch is that treatment doesn’t undo damage already done. Scar tissue in the fallopian tubes or epididymis remains after the bacteria are gone, which is why early detection matters so much.
Reinfection is common. The CDC notes a high rate of chlamydia among people who were treated in the preceding months, and the majority of these repeat infections come not from treatment failure but from untreated sexual partners or new partners who carry the infection. This is why retesting three months after treatment is strongly recommended, regardless of whether you believe your partner was also treated. If your partner wasn’t tested and treated at the same time, the bacteria simply pass back and forth.
Each reinfection carries its own risk of complications. Repeated chlamydia infections compound the damage to reproductive tissue, making infertility and ectopic pregnancy progressively more likely with each episode. Ensuring that all sexual partners receive treatment simultaneously is one of the most effective ways to break this cycle.