Sexually Transmitted Infections

What is a sexually transmitted infection?

A sexually transmitted infection (also called STI, sexually transmitted disease or STD) is an infection you can get from having unprotected sex or intimate physical contact with someone who is infected. You can get an STI from having unprotected vaginal, anal or oral sex. You can get an STI even if you’re pregnant—being pregnant doesn’t protect you from getting infected.

STIs can be caused by bacteria, viruses or parasites. Many people with STIs don’t know they’re infected because they often have no signs or symptoms. Nearly 26 million new STI infections were reported in 2018 in the United States.  

Some STIs can spread in ways other than sex. For example, you can get some STIs, like HIV, syphilis and herpes, by having direct contact with body fluids from an infected person. This can happen by genital touching, touching or kissing an infected sore (in the case of syphilis) or by sharing drug needles or other items that come in contact with body fluids from an infected person.

Bacterial vaginosis (also called BV or vaginitis) is an infection caused when there’s too much of certain bacteria in the vagina. It’s not an STI, but you’re more likely to get it if you have a new sex partner or more than one sex partner. If you have BV, you’re at increased risk of getting an STI.

You can pass some STIs to your baby during pregnancy, labor, birth and breastfeeding. STIs can cause serious problems for babies. Early testing and treatment can help protect your baby from infection.

How can you protect yourself and your baby from STIs?

The best way to protect your baby from STIs is to protect yourself from STIs. If you have an STI, the best way to protect your baby is to get early and regular treatment during pregnancy.

Here’s what you can do to reduce your risk and your baby’s risk for infection:

• Don’t have sex. Sex includes vaginal, oral and anal sex.
• Limit the number of sex partners you have. Have sex with only one person who doesn’t have other sex partners.
• Use a condom every time you have sex. Condoms are barrier methods of birth control. Barrier methods help prevent pregnancy and STIs by blocking or killing your partner’s sperm. Male latex condoms work best to prevent STIs; other kinds of condoms don’t work as well. Other kinds of birth control, like the pill and implants, don’t protect you from STIs.  When using a condom be sure your partner is using it correctly. This guide has some helpful information.
• Don’t share needles, syringes, razors or other things that may come in contact with another person’s blood or body fluid.
• Get tested and treated. Early testing and treatment can help reduce the risk of passing an STI to your baby. Ask your partner to get tested and treated, too. Even if you get treated for an STI, you can get re-infected (get the infection again) if your partner is infected.
• Go to all your prenatal care checkups, even if you’re feeling fine. You may have an STI and not know it. If you think you may have an STI, tell your health care provider so you can get tested and treated right away.
• Get vaccinated. Vaccinations can help protect you from some STIs, like hepatitis B and some types of human papillomavirus (also called HPV). Vaccinations are shots that contain a vaccine that helps make you immune to certain diseases. If you’re immune to a disease, you can’t get the disease.

What problems can STIs cause during pregnancy?   

Having an STI during pregnancy can cause serious problems for you and your baby, including:

• Preterm birth. This is birth that happens too soon, before 37 weeks of pregnancy. Premature babies can have serious health problems at birth and later in life.
• Low birthweight. This is when a baby is born weighing less than 5 pounds, 8 ounces.
• Premature rupture of the membranes (also called PROM). This is when the sac around your baby breaks (your water breaks) before you go into labor.
• Pelvic inflammatory disease (also called PID). PID is an infection of a woman’s reproductive organs.  Reproductive organs include the uterus (also called womb), fallopian tubes, ovaries and cervix. These organs all play a part in pregnancy. PID can make it hard for you to get pregnant. During pregnancy, it can lead to problems like ectopic pregnancy. An ectopic pregnancy is when an embryo (fertilized egg) grows in the wrong place outside the womb, like the fallopian tube. This can cause serious problems for you and always ends in pregnancy loss.
• Miscarriage. This is when a baby dies in the womb before 20 weeks of pregnancy.
• Stillbirth. This is when a baby dies in the womb after 20 weeks of pregnancy.

Having an STI can cause problems for your baby after birth, too, like problems with the eyes, lungs and liver. Some of these problems can affect your baby’s entire life, and some can even cause death. This is why it’s important to get tested and treated for STIs. Treatment before and during pregnancy can help protect your baby from infection.

How do you know if you have an STI?

STIs often have no signs or symptoms, so you may not know you’re infected. Common signs and symptoms of STIs include:

• Flu-like symptoms, including fever, headache and fatigue (feeling very tired)
• Vaginal discharge or burning, itching, redness or swelling in the vaginal area
• Pain, itching or burning when you go to the bathroom; pain, discharge or bleeding in the rectum (where bowel movements leave the body); or painful bowel movements
• Belly pain
• Pain during sex or bleeding after sex or between periods
• Eye infections
• Sores on the mouth or the vaginal, genital or anal areas

As part of your prenatal care (medical care you get during pregnancy), your provider tests you for certain STIs, including:

Chlamydia and gonorrhea. These STIs are most common in women younger than 25. Most infected women have no signs or symptoms. You’re tested for these STIs with a urine test or a swab of fluids from the vagina. 

Genital herpes. You can get genital herpes from unprotected sex or through direct contact with an infected person’s herpes sore or fluid from a herpes sore. Having genital herpes during pregnancy can cause serious health problems for your baby, including brain infection (also called herpes encephalitis); eye diseases; infection of the liver, lungs, kidneys, skin and mouth; and even death. You’re most likely to pass herpes to your baby if you have genital herpes sores and blisters (called an outbreak) for the first time late in pregnancy. You get tested for genital herpes with a blood test or if you provider takes a tissue sample from a sore.

Hepatitis B (also called hep B). You can get hep B from unprotected sex or through direct contact with infected body fluids, like blood, saliva, semen and vaginal fluid. It spreads easily through breaks in the skin or in soft body tissues in the nose, mouth and eyes. If untreated, hep B can damage your liver. Many infected women have no signs or symptoms, but some may have jaundice. This is when your liver isn’t working properly so your eyes and skin look yellow. The Centers for Disease Control and Prevention (also called CDC) recommends that all pregnant women get a blood test for hep B and that any adult, including pregnant women, at risk for hep B gets vaccinated. You can get vaccinated even if you’re not at risk for hep B. If you’re pregnant and you test positive for hep B, you get another test that can help your provider know if your baby’s at risk for infection. Babies with hep B can have life-long health problems, including liver problems. CDC recommends that all babies get vaccinated for hep B within 24 hours after birth and later as part of their regular vaccination schedule, and that all babies born to women with hep B get vaccinated within 12 hours after birth and treated for hep B at birth.

HPV. HPV is the most common STI in the United States. In most cases, HPV goes away on its own. But if it doesn’t, it can cause genital warts (small bumps in the genital area) and cancer of the cervix (also called cervical cancer). The CDC recommends women up to age 26 get the HPV vaccination to protect them from HPV. If you’re pregnant and have an HPV infection with genital warts, you may get more warts during pregnancy. They may grow large enough to block the vagina. If this happens, you may need to have a cesarean birth (also called c-section). A c-section is surgery in which your baby is born through a cut your doctor makes in your belly and uterus (womb). It is possible to pass HPV from mother to baby during pregnancy. If it does happen, in rare cases it can cause warts to grow on the baby’s voice box (also called larynx). You get tested for HPV with a Pap test.

Human immunodeficiency virus (also called HIV). HIV is a virus that attacks the body’s immune system. The immune system protects the body from infections, cancers and some diseases. If untreated, HIV can lead to acquired immune deficiency syndrome (also called AIDS). In the United States, HIV is most commonly spread through unprotected sex with or by sharing drug needles with an infected person. Having HIV can make it easier for you to get infected with other STIs. If you have HIV, early and regular treatment during pregnancy can help protect your baby from infection. You get tested for HIV with a blood test.

Syphilis. You can get syphilis from unprotected sex or through direct contact with (touching or kissing) an infected person’s syphilis sore. If not treated, syphilis can damage your eyes, heart, brain and spinal cord. If you have syphilis, early and regular treatment during pregnancy can help protect your baby from infection. When a baby is born with syphilis, it’s called congenital syphilis. Congenital syphilis is completely preventable, but many babies born to moms with untreated syphilis may have many health problems or may die from the infection. The best way to protect your baby from congenital syphilis is to prevent infection before and during pregnancy. You get tested for syphilis with a blood test.  You can also get treated for syphilis during pregnancy.

Zika. Your provider may test you for Zika if you have signs or symptoms of infection or if you or your partner has been in an area where Zika is spreading. Zika is a virus that spreads mainly through mosquito bites and unprotected sex with an infected person. Zika often has no signs or symptoms so you may not know you’re infected. If you have Zika during pregnancy, it causes a birth defect called microcephaly that’s part of a condition called congenital Zika syndrome. If you’re pregnant and you think you’ve been exposed to Zika before or during pregnancy, tell your provider right away.

Ask your provider about getting tested for STIs during pregnancy. Find out which tests you get and when you get them. If you think you may have an STI, tell your provider.

How are STIs treated?

Early testing and treatment can help protect you and your baby from most STIs.

If you have an STI that’s caused by bacteria, your provider prescribes antibiotics to treat it. Bacteria are tiny organisms that live in and around your body. Some bacteria are good for your body, and others can make you sick. Antibiotics are medicines that kill infections caused by bacteria.

STIs that are caused by a virus (like HIV, HPV, herpes or hepatitis) can’t be cured with treatment. But treatment can help you manage signs and symptoms.  Some medicines can help lower the risk of passing a viral STI like herpes or HIV to your baby. Talk to your provider about what treatments you may need if you have an STI.

More information

• CDC’s STD and pregnancy fact sheet
• CDC’s The Lowdown infographic

Last reviewed: June, 2022