If a pregnant person has chlamydia, they can give the infection to their baby during delivery, which can cause an eye infection or pneumonia in the baby
Having chlamydia may also make it more likely to deliver the baby early
In women, it can cause pelvic inflammatory disease, which can lead to formation of scar tissue that blocks fallopian tubes, ectopic pregnancy, infertility, and long-term pelvic/abdominal pain
In men, it can cause a fever and pain in the tubes attached to the testicles, which can in rare cases lead to infertility
Untreated chlamydia may also increase your chances of getting or giving HIV