What is an STI?

Sexually transmitted infections (STIs) are infections that can be passed on during sexual activity. If you are pregnant, STIs can also be transmitted from you to your unborn baby. If left untreated, STIs can cause serious problems for both you and your baby.

What causes STIs?

STIs are caused by microorganisms such as bacteria, viruses and parasites, and are sometimes called sexually transmitted diseases (STDs). These organisms can pass between people in semen, blood or vaginal and other bodily fluids.

Many STIs can also be transmitted by:

• close skin-to-skin contact (for example, during foreplay)
• blood-to-blood contact
• sharing needles and other equipment for intravenous (IV) drug use

STIs can also be passed from you to your baby during pregnancy and childbirth.

What are the different types of STIs?

There are many different types of STIs. The most common STIs in Australia are:

• chlamydia
• gonorrhoea
• syphilis
• genital herpes
• genital warts / human papilloma virus (HPV)
• hepatitis B
• human immunodeficiency virus (HIV)
• trichomoniasis

There are also other infections that, while not strictly classified as STIs, may be linked with sexual activity, such as:

• hepatitis A
• thrush
• bacterial vaginosis
• pubic lice (‘crabs’)
• scabies
• lymphogranuloma venereum
• mycoplasma genitalium

What are the symptoms of STIs?

Many people with STIs have no symptoms. You might not even know you have an STI until it causes complications, or a sexual partner is diagnosed.

Some people get symptoms such as:

• sores or bumps on the genitals, mouth or rectal area
• pain when urinating or during sex
• unusual discharge from the penis or vagina
• unusual vaginal bleeding

If you have one or more of these symptoms, it doesn’t necessarily mean you have an STI. But it’s still a good idea to see your doctor for a check-up.

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

FIND A HEALTH SERVICE — The Service Finder can help you find doctors, pharmacies, hospitals and other health services.

Can having an STI affect my pregnancy?

STIs can affect your ability to become pregnant (your fertility), as well as your pregnancy. Pregnancy doesn’t prevent you getting an STI. If you are infected with an STI while you’re pregnant, it can cause serious problems for you and your developing baby.

If you are pregnant, or wanting to become pregnant, you should ask your doctor to test you for STIs, even if you have tested in the past. If you have concerns about this, discuss them with your doctor, or a health professional at your local sexual health clinic.

If you do catch an STI while you’re pregnant, getting early treatment can reduce the risks. Even if the STI can’t be cured, there are things that can be done to protect you and your baby.

How can STIs affect my baby?

Some STIs, such as syphilis and HIV, can infect a baby still while you’re pregnant. Others, such as chlamydia and genital herpes, can infect the baby during labour and/or birth.

STIs can pose significant health risks to unborn babies. These include:

• transmission of the infection to the baby
• premature birth
• low birth weight
• birth differences (defects)
• stillbirth

Getting regular medical care during your pregnancy and discussing any concerns you have regarding STIs with your doctor or midwife help reduce the risk of problems caused by STIs during your pregnancy.

How are STIs diagnosed and treated?

Untreated STIs stay active in the body and may be passed on to sexual partners, or your baby, without you being aware. Therefore, it’s important to get tested if you think you may have an STI.

Having a test for STIs is simple. The type of test depends on the STI, but tests usually involve providing a urine sample, a swab, a blood test or having a physical examination. If the test shows you have an STI, you may need further tests and treatment.

STIs caused by bacteria, such as chlamydia, can usually be treated with antibiotics. Other STIs, such as those caused by viruses (for example, herpes) are not always curable, but there may be things you can do to relieve your symptoms.

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

Will I be tested for STIs during pregnancy?

Most people will be offered routine tests for some STIs at their first antenatal care appointment, including:

• hepatitis B
• HIV
• syphilis

Depending on your age and circumstances, your doctor may recommend testing for other STIs as well.

What can I do to avoid getting an STI?

Other than not having sex with a partner who could potentially have an STI, practicing safe sex with condoms (used during penetrative sex) and dental dams (used during oral sex) offers the best protection from STIs.

Other ways to avoid STIs are:

• having sex with one uninfected partner
• limiting the number of sexual partners you have sex with
• avoiding sex with a new partner until you’ve both been tested for STIs
• getting vaccinated against HPV and hepatitis
• not taking drugs or drinking excessive alcohol (often associated with risk-taking behaviour)

If you are male, getting circumcised reduces your chances of catching some STIs too.

Resources and support

• The Australian Government Department of Health and Aged Care has information about looking after your sexual health.
• The Royal Women’s Hospital, Victoria has fact sheets on Having a pelvic or genital examination.
• ReachOut has information and advice about STIs for young people.
• Do you prefer to read languages other than English? Talk Test Treat website has STI information in a range of languages.