Sexually transmitted infections (STIs) are infections spread by sexual contact. If you're pregnant, you can also spread them to your baby before or during delivery. STIs are also called sexually transmitted diseases (STDs). Some examples of STIs include chlamydia, gonorrhea, syphilis, human papillomavirus (HPV), and human immunodeficiency virus (HIV).

You can be exposed to an STI anytime you have sex or close contact with the genitals, mouth, or rectum of another person. But exposure is more likely if you have more than one sex partner or you don't use condoms. Using condoms can reduce the risk of STIs. STIs can be prevented by not having sexual contact. (This is called abstinence.)