What is an STI?
Sexually transmitted infections (STIs) are infections that can be passed on during sex, and in some cases can be passed from mother to child. If left untreated, STIs can cause serious problems for both mother and child. If you think you may have an STI, it’s important to see a doctor.
STIs are caused by micro-organisms 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), through blood-to-blood contact, and by sharing needles and other equipment for intravenous drug use.
STIs can also be passed from a woman to her 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 (a bacterial infection)
- gonorrhoea (a bacterial infection)
- syphilis (a bacterial infection)
- genital herpes (a viral infection)
- genital warts/human papilloma virus (HPV) (a viral infection)
- hepatitis B (a viral infection)
- HIV (a viral infection)
- trichomoniasis (a parasite)
There are also other infections that, while not strictly classified as STIs, are sometimes linked with sexual activity, such as:
- hepatitis A (a viral infection)
- thrush (a fungal infection)
- bacterial vaginosis (an imbalance of bacteria in the vagina)
- pubic lice or crabs (a parasite)
- scabies (a parasite)
- lymphogranuloma venereum (a bacterial infection)
- mycoplasma genitalium (a bacterial infection)
What are the symptoms of STIs?
Many people with STIs have no symptoms. They may not know about it until it causes complications or a partner is diagnosed.
Other people get symptoms such as:
- sores or bumps on the genitals, mouth or rectal area
- pain when urinating
- unusual discharge from the penis or vagina
- unusual vaginal bleeding
- pain during sex
- sore, swollen lymph nodes, especially in the groin
- pain in the lower abdomen
- rash on the body, hands or feet
If you have one or more of these symptoms it doesn’t necessarily mean you have an STI, but it would be wise to see your doctor for a check-up.
Can having an STI affect my pregnancy?
STIs can affect your ability to become pregnant (your fertility), as well as your pregnancy. Women who are pregnant can get the same STIs as women who are not pregnant. If you get infected with an STI while pregnant, it can cause serious problems for you and your developing baby.
If you are pregnant, or wanting to become pregnant, it is recommended that you are tested for STIs even if you have been tested in the past. If you have concerns about this, discuss them with your doctor.
If you do contract an STI while 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 while it’s still in the mother’s womb. Others, such as chlamydia and genital herpes, can infect the baby as it is being delivered.
STIs can pose significant health risks to unborn babies. These include:
- transmission of the infection to the baby
- premature birth
- low birth weight
- birth defects
Getting regular medical care during your pregnancy and discussing any concerns you may have of STIs with your doctor or midwife help reduce the risk of any 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 a providing a urine sample, a swab, a blood test, or a physical examination.
If the test shows you have an STI, you may need further tests and treatment. STIs caused by bacteria, like chlamydia, can usually be treated with antibiotics. Other STIs, such as those caused by viruses (for example herpes), can be managed to control symptoms, but are not always curable.
Tips for avoiding STIs
Other than not having sex with a partner that could potentially have an STI, condoms (used during penetrative sex) and dental dams (used during oral sex) offer the best protection from STIs.
Other ways to avoid STIs are:
- staying with one uninfected partner or not having many sexual partners
- avoiding sex with a new partner until you’ve both been tested for STIs
- getting vaccinated against HPV and hepatitis
- getting circumcised (if you are a man)
- not taking drugs or drinking excessive alcohol (often associated with risk-taking behaviour)
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Last reviewed: December 2020