The bacterium Chlamydia trachomatis causes one of the most commonly reported sexually transmitted infections worldwide. This infection is often silent, with a majority of people—up to 70% of women—experiencing no noticeable symptoms. When untreated, the bacteria can remain in the body undetected for extended periods, allowing the infection to migrate beyond the initial site of infection. This extended duration is directly linked to the development of complications that can permanently affect reproductive capacity, increasing the probability of developing infertility.
The Pathway to Reproductive Damage
The damage that leads to infertility begins when Chlamydia trachomatis bacteria ascend from the lower genital tract to the upper reproductive organs. This upward spread triggers a sustained inflammatory response. In individuals with female anatomy, this progression leads to Pelvic Inflammatory Disease (PID), involving the uterus, ovaries, and fallopian tubes.
As the inflammation subsides, it often leaves behind scar tissue and adhesions within the delicate fallopian tubes. This scarring can partially or completely block the tubes, preventing sperm from reaching the egg or preventing a fertilized egg from traveling to the uterus. This outcome is referred to as tubal factor infertility.
In individuals with male anatomy, the untreated infection can also spread, commonly causing epididymitis, which is the inflammation of the coiled tube that stores and carries sperm. This inflammation can lead to scarring and obstruction, potentially reducing fertility by affecting sperm delivery. Studies also suggest that untreated chlamydia may cause direct damage to the DNA within sperm cells, impacting their health and motility.
Calculating the Risk: Duration of Untreated Infection
It is impossible to provide a precise timeline after which chlamydia causes irreversible infertility. The progression of damage is highly individual, depending on factors like the specific immune response, the severity of the inflammatory reaction, and whether the infection is a first or repeat episode. The consensus among health professionals is that the risk of reproductive damage is cumulative, increasing proportionally with the duration the infection remains active in the body.
For women, the development of PID is the critical point, which occurs in an estimated 10% to 15% of untreated chlamydia cases. While PID can occur at any point during an active infection, data suggest that the risk increases significantly over time. For example, some estimates suggest that one in ten women with untreated chlamydia may develop PID within one year.
Once PID has occurred, the risk of subsequent tubal factor infertility is established, even after the infection is cleared. A single episode of PID can lead to tubal damage, and approximately 10% to 20% of women who experience chlamydia-related PID may develop infertility. This probability increases sharply with each repeat infection, as recurring episodes cause further inflammation and cumulative scarring within the fallopian tubes.
Recent research suggests that symptomatic chlamydia infections, which cause noticeable discomfort, may be associated with a higher risk of adverse reproductive outcomes compared to asymptomatic cases. However, since most infections are silent, they often progress without the individual being aware of the ongoing damage. The timeline for damage is highly variable, underscoring the danger of the infection’s asymptomatic nature.
Testing, Treatment, and Preventing Future Damage
Chlamydia is highly treatable with a simple course of antibiotics, which effectively clears the bacterial infection. Successful treatment halts the inflammatory process, immediately stopping the progression of damage that could lead to infertility. This intervention is most effective when administered quickly, before significant scarring has developed in the reproductive organs.
A limitation of treatment is that antibiotics cannot reverse existing structural damage, such as scar tissue or blockages that have already formed in the fallopian tubes. Therefore, early detection is essential to preventing permanent damage to fertility. Screening is typically performed using Nucleic Acid Amplification Tests (NAATs) on urine samples or swabs, which are highly accurate.
Health organizations recommend annual screening for all sexually active women under the age of 25, as well as older women who have risk factors like new or multiple sex partners. Prevention strategies also focus on safe sex practices, including the consistent and correct use of barrier methods. When an infection is diagnosed, all recent sexual partners must be notified and treated to prevent reinfection, which increases the cumulative risk of damage.