Several infections can damage a woman’s reproductive system enough to cause infertility, with chlamydia and gonorrhea being the most common culprits. The danger with these infections is that they often cause no symptoms at all, silently scarring the fallopian tubes and uterus while a woman has no idea anything is wrong. About 100,000 women in the U.S. develop infertility each year as a direct result of pelvic inflammatory disease, which is most often triggered by untreated sexually transmitted infections.
Chlamydia and Gonorrhea: The Silent Threats
Chlamydia is the infection most strongly linked to female infertility, largely because it so rarely announces itself. Around 70% of women with chlamydia have no noticeable symptoms. Gonorrhea is similarly quiet, with at least 50% of infected women showing no signs. Without symptoms, there’s no obvious reason to get tested, and the bacteria keep doing damage.
Both infections target the reproductive tract. Left untreated, they can climb from the cervix into the uterus, fallopian tubes, and ovaries, triggering a condition called pelvic inflammatory disease (PID). About 10 to 15% of untreated chlamydia infections in women progress to PID. The immune system’s aggressive response to these bacteria causes inflammation and, eventually, permanent scarring in the reproductive organs.
That scarring is what blocks fertility. When scar tissue forms inside the fallopian tubes, it can partially or fully block the path an egg needs to travel. A partial blockage raises the risk of ectopic pregnancy, where a fertilized egg implants in the tube instead of the uterus. A complete blockage prevents conception entirely. Roughly 1 million women in the U.S. develop PID each year, and the damage accumulates with each episode. One study tracking women after a PID episode found that 40% were involuntarily infertile afterward.
How Blocked Tubes Poison the Environment
When infection scars a fallopian tube shut, fluid can accumulate inside it, creating a condition called hydrosalpinx. This isn’t just a physical blockage. The trapped fluid is actively toxic to sperm and embryos. Research shows it contains growth-factor inhibitors and other substances that reduce sperm motility and interfere with embryo development. In lab studies, mouse embryos exposed to this fluid had significantly lower development scores and smaller yolk sacs.
Even in women undergoing IVF, where fertilization happens outside the body, hydrosalpinx fluid can leak back into the uterus and reduce the chances of a transferred embryo implanting. This is why fertility specialists often recommend removing a damaged tube before attempting IVF, counterintuitive as that sounds.
Chronic Endometritis: Infection of the Uterine Lining
Chronic endometritis is a low-grade, persistent infection of the uterine lining that often flies under the radar. It doesn’t cause the dramatic symptoms of acute PID. Instead, it creates an environment where embryos struggle to implant. Women with chronic endometritis who undergo IVF have a clinical pregnancy rate of about 53%, compared to 80% in women without the condition. Implantation rates drop from roughly 65% to 47%.
The condition is found in about 30% of women experiencing repeated implantation failure during fertility treatment. It’s caused by bacteria that colonize the uterine lining and trigger a chronic immune response, keeping the tissue in a state of mild inflammation that makes it inhospitable to an embryo. The good news is that once identified, it typically responds well to antibiotic treatment, and pregnancy rates often improve afterward.
Mycoplasma Genitalium
Mycoplasma genitalium is a lesser-known sexually transmitted bacterium that has emerged as a significant risk factor for female infertility. A large meta-analysis found that women infected with this organism had roughly 13 times the odds of infertility compared to uninfected women. Like chlamydia, it can cause cervicitis and ascend into the upper reproductive tract, leading to PID and tubal damage.
Testing for Mycoplasma genitalium is not yet part of routine STI screening in most clinics, which means it may go undetected in women experiencing unexplained fertility problems. If you’ve been tested for chlamydia and gonorrhea with negative results but still have signs of cervicitis or PID, this is one infection worth asking about specifically.
Bacterial Vaginosis and Fertility
Bacterial vaginosis (BV) is not a traditional infection but an imbalance in the vaginal microbiome, where protective bacteria are overtaken by other species. Its link to infertility is less direct than chlamydia or gonorrhea, but it does appear to affect pregnancy outcomes. In one prospective study of women undergoing IVF or intrauterine insemination, 26% tested positive for BV. Those who were BV-positive had a miscarriage rate of 60%, compared to 25% in BV-negative women.
Ongoing pregnancy rates were also lower in the BV-positive group, though the difference didn’t reach statistical significance in that particular study. The effect appeared stronger in IVF cycles than in insemination cycles. BV likely interferes more with maintaining a pregnancy than with conception itself, but for women already struggling with fertility, it’s one more factor worth addressing.
Genital Tuberculosis
In countries where tuberculosis is common, genital TB is a major but often overlooked cause of infertility. The infection spreads through the bloodstream to the reproductive organs and affects both fallopian tubes in over 90% of cases. It also involves the uterine lining in about 70% of cases and the ovaries in 20 to 30%. The disease is frequently diagnosed for the first time when a woman seeks help for infertility.
Genital TB is rare among women born in the United States, but fertility specialists increasingly recognize that women originally from endemic regions (parts of South Asia, sub-Saharan Africa, and Southeast Asia) may benefit from tuberculosis screening as part of an infertility workup. The infection is difficult to diagnose because it produces very few bacteria in the genital tract and can be entirely asymptomatic.
Why Screening Matters Before You Try to Conceive
The CDC recommends annual chlamydia and gonorrhea screening for all sexually active women under 25, and for older women with risk factors like new or multiple partners. These recommendations exist precisely because these infections are so often silent. Getting tested and treated before the bacteria have time to cause PID is the most effective way to protect your fertility.
If you’re planning to conceive and have any history of STIs, pelvic pain, unusual discharge, or irregular bleeding, a more thorough evaluation of your reproductive tract can catch problems like chronic endometritis or tubal damage before you spend months wondering why you aren’t getting pregnant. The infections themselves are almost always treatable with antibiotics. The scarring they leave behind is not.