For many years, home pregnancy tests have been most women’s first choice to confirm their suspicion they might be pregnant. Home pregnancy tests are inexpensive, disposable kits available over-the-counter from most pharmacies in Australia, some supermarkets also sell them and they can also be purchased online.
Using a home pregnancy test is a great way to choose a time and place where you’re most comfortable, before getting a pretty accurate result on whether or not conception was a success.
Home pregnancy tests are sensitive, once-off test kits that respond to the presence of a hormone called human chorionic gonadotrophin – hCG – in urine. This hormone is released when the fertilised egg first implants in the uterus, usually between 8 and 10 days after fertilisation has occurred (though it can be anywhere from 6-12 days!)
Levels of hCG will rise quickly in the first few days after following implantation and peak between 50 and 80 days after fertilisation. Within about two weeks, usually when your period is due, the hormone can be easily detected in urine.
Some home pregnancy tests are highly sensitive and can pick up quite low levels of hCG in urine, giving a response up to a week after implantation.
More sensitive tests are usually more costly and will detect a concentration of 20 mIU (which is about 20 parts per one thousandth of a millilitre); while the stock-standard tests will only give a result when there is 50 mIU – which will happen a few days later.
The sensitivity of the home pregnancy test will be marked on the box; the most popular tests are currently 20, 25, 40, 50 or 100 miU.
Home pregnancy tests come with detailed instructions and information, and it’s wise to follow the instructions carefully.
You can usually perform the test any time of day, and use the test from the first day that your period was due. Many women choose to do the test first thing in the morning, when the hormone levels in the urine are likely to be at their highest.
Test results can be affected by fertility drugs containing hCG hormones and can also be affected if you have had a lot of fluid to drink shortly before taking the test – as this can dilute the urine. But other medications are unlikely to affect test results.
Home pregnancy tests differ in the way that they need you to collect urine.
For some home pregnancy tests, the plastic stick containing the test strip should be held a few centimeters underneath you, while you wee directly onto the stick; other tests supply a small plastic container for collecting the urine, which you then put onto the test stick with a dropper.
The way that the test results appear, will depend on the way the manufacturer prepared the kit. Do check the instructions carefully to see what to expect.
In many tests, the response will appear as two lines, parallel or crossed. One ‘control’ result line will ALWAYS appear; but the second result line will only appear in response to the presence of hCG – so that’s two lines for pregnant, one line for not pregnant.
Some tests reveal a plus or minus sign, or spell the words ‘pregnant’ or ‘not pregnant;’ and some change colour; test results might be red, pink or blue.
Most tests will give a result in five minutes. Try to find something to occupy you for that five minutes, as it will seem like an eternity! It’s excruciating to sit there and watch the test to change.
Most home pregnancy tests are around 97% accurate, provided that you follow the instructions exactly. If you have a very irregular cycle, it can be difficult to determine whether the time is right to test.
False negatives (when you are pregnant but the test doesn’t show this) occur if you test too early, or if your body is not making the expected amount of the hCG hormone.
If you get a negative result but you still feel you might be pregnant, wait three days then try another test.
False positives (when the test says you’re pregnant but you’re not) might occur if you have taken a fertility drug which contains hCG or if there is an error in the test.
Many doctors use urine tests that are exactly the same as home pregnancy tests to verify pregnancies. However, if there is some uncertainty about results, your doctor may order a blood test which will also test hCG levels, but is usually more sensitive than a urine test.
By Fran Molloy, journalist and mum of four