Think you might be pregnant? Dr Sally Sweeney, Medical Officer at Family Planning NSW says modern home pregnancy tests currently sold in Australia can give you an accurate answer.

"If a woman has done a positive pregnancy test at home there is generally no need to repeat it unless there is some doubt or concern, or the woman wishes to repeat the test with the doctor."

Here's what you need to know about at-home pregnancy tests…

How do pregnancy tests work?

Home pregnancy tests work by detecting the hormone produced during pregnancy (Human chorionic gonadotropin or hCG) in the urine. The test uses special dyes to show lines or symbols on a test strip. One line or symbol is a control to show whether the test is working, and a second line or symbol appears if hCG is present in the urine being tested. Some tests are digital and use an electronic reader to show the result.

"Most women have done a home test before coming to the doctor. Some women come to do one at the doctors as they think the ones used in clinic are more accurate but in fact, they are the same as a home pregnancy test. If there is any doubt a doctor can order a blood test which is more accurate than urine testing," explains Dr Sweeney.

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How accurate are pregnancy tests?

In 2017 the Therapeutic Goods Administration (TGA) conducted a review of all home pregnancy test kits sold in Australia. This followed the discovery at a Family Planning NSW clinic that one brand of test kit was giving false negative results, or wrongly indicating that a woman was not pregnant when she was.

The review found some devices were not working correctly and they were either removed from the market or corrected. All devices currently available in Australia have been found to be reliable and accurate, and must be included on the Australian Register of Therapeutic Goods (ARTG).

Are cheap tests less accurate than expensive ones?

As long as a kit has been approved by the TGA for the Australian market it should be accurate. Often more expensive tests may use fancier electronic results indicators, or may be more user friendly "in stream" kits rather than "dip sticks". The tests themselves should be equally reliable regardless of price. Sometimes, more expensive kits may claim to give an earlier result.

Most women have done a home pregnancy test before coming to the doctor. *Image: Getty Images.

How soon can you take a test?

Most Australian pregnancy test kits will detect pregnancy hormone levels at around the time a woman has missed her period. Some claim to be able to detect lower levels of hormone up to a week before a period is due.

Testing too early may miss an early pregnancy however, so it is best to wait until a period has been missed or is late to get a more reliable result. This is because higher levels of hormone are present as the time progresses. A woman with an irregular cycle can generally expect to have a positive test three weeks after conception.

Women with a positive pregnancy test should see a doctor to discuss her wishes for the pregnancy, important pregnancy care steps and to arrange any referrals.