What are sexually transmitted infections (STIs)?

Sexually transmitted infections (STIs) are infections that are spread by sexual contact. STIs can cause severe damage to your body—even death. Except for colds and flu, STIs are the most common contagious (easily spread) infections in the United States, with millions of new cases each year. Although some STIs can be treated and cured, others cannot.

How are STIs transmitted?

A person with an STI can pass it to others by contact with skin, genitals, mouth, rectum, or body fluids. Anyone who has sexual contact—vaginal, anal, or oral sex—with another person may get an STI. STIs may not cause symptoms. Even if there are no symptoms, your health can be affected.

What causes STIs?

STIs are caused by bacterial or viral infections. STIs caused by bacteria are treated with antibiotics. Those caused by viruses cannot be cured, but symptoms can be treated.

What are the risk factors for STIs?

The following factors increase the risk of getting STIs:

What are some of the most common STIs?

How can I reduce the risk of getting an STI?

There are many ways you can reduce your risk of getting an STI:

How can STIs affect pregnancy?

Having an STI during pregnancy can harm the fetus. Gonorrhea and chlamydia both can cause health problems in the infant ranging from eye infections to pneumonia. Syphilis may cause miscarriage or stillbirth. HIV infection can pass to a baby during a vaginal birth.

If you are pregnant and you or your partner have had—or may have—an STI, inform your health care professional. Your fetus may be at risk. Tests for some STIs are offered routinely during prenatal care. It is best to treat the STI early to decrease the chances that your fetus will get the infection. You and your partner both may have to be treated.


Antibiotics: Drugs that treat certain types of infections.

Source: acog.org