Risk factors

Anyone who is sexually active risks some degree of exposure to an STD or STI. Factors that may increase that risk include:

• Having unprotected sex. Vaginal or anal penetration by an infected partner who isn't wearing a latex condom significantly increases the risk of getting an STI. Improper or inconsistent use of condoms can also increase risk.

  Oral sex may be less risky, but infections can still be transmitted without a latex condom or a dental dam — a thin, square piece of rubber made with latex or silicone.

• Having sexual contact with multiple partners. The more people you have sexual contact with, the greater your risk.
• Having a history of STIs. Having one STI makes it much easier for another STI to take hold.
• Being forced to engage in sexual activity. Dealing with rape or assault is difficult, but it's important to see a doctor as soon as possible to receive screening, treatment and emotional support.
• Misuse of alcohol or use of recreational drugs. Substance misuse can inhibit your judgment, making you more willing to participate in risky behaviors.
• Injecting drugs. Needle sharing spreads many serious infections, including HIV, hepatitis B and hepatitis C.
• Being young. Half the new STIs occur in people between the ages of 15 and 24.

Transmission from mothers to infants

Certain STIs — such as gonorrhea, chlamydia, HIV and syphilis — can be passed from mothers to their infants during pregnancy or delivery. STIs in infants can cause serious problems or even death. All pregnant women should be screened for these infections and treated.