Home pregnancy tests are a convenient, accurate and inexpensive way to test if you are pregnant.
1. How do pregnancy tests work?
Home pregnancy tests check urine for a hormone called human chorionic gonadotropin (hCG) which the body makes only during pregnancy. Some call hCG ‘the pregnancy hormone’. A ‘positive test’ means that hCG is detected in your urine and you are pregnant.
When a fertilised egg attaches to the lining of the uterus, ‘implantation’ has occurred which is the time that women become pregnant. Increasing amounts of hCG is produced after implantation when the placenta begins to develop.
Increasing hCG levels can cause pregnancy symptoms such as nausea and fatigue. hCG levels peak at about 10 weeks of pregnancy, then plateaus or reduces for the rest of pregnancy.
2. Are home pregnancy tests accurate?
In 2017, the Therapeutic Goods Administration (TGA) completed a thorough review of all home pregnancy tests available in Australia to ensure that those on the market were reliable and accurate. Products that were found not to work reliably or accurately were corrected by manufacturers or removed from the market.
The TGA is Australia’s regulatory authority responsible for regulating therapeutic goods, such as prescription medications, vaccines, sunscreens and medical devices.
Pregnancy tests sold online from overseas may not be regulated by the TGA so may not have been tested for reliability or accuracy. As part of the 2017 review, two types of pregnancy tests sold on eBay were shown to be inaccurate and unreliable.
Pregnancy tests claim to be 99% accurate if used after a missed period. Missed period is the day after the day you expect your period: if your period is due on 1 January then your missed period is 2 January. This accuracy is based on a manufacturer’s own laboratory testing under certain scientific conditions. However in the real world, many women are confused about how to use tests, and especially how to interpret results when sometimes the coloured line on tests can be faint. Some brands use symbols or words instead of coloured lines to help people interpret results more easily.
3. How soon can I take a pregnancy test?
If you’re trying to conceive, you will be constantly wondering if you’re pregnant as soon as your fertile window has passed. Some pregnancy tests claim they can detect pregnancy several days before a missed period.
Examples of ‘early detection pregnancy tests’ are the First Response Early Result In-Stream Pregnancy Test and Clearblue Early Detection Pregnancy Test. They both claim to detect pregnancy 6 days before a missed period.
But taking a test too early may mean that hCG isn’t high enough yet to get a positive test result. So if you test early and your test is negative, there is still a chance that you may be pregnant.
Remember that you become pregnant after implantation. Implantation can occur 7-10 days after you ovulate so testing too early may be unrealistic anyway since implantation may not have occurred yet.
It is more accurate to take a pregnancy test 1-2 weeks after a missed period which is when hCG levels are higher. hCG levels double every 2-3 days in early pregnancy so if you get a negative result or a very faint line at first then you can try another test after 3 days.
Personally, I preferred not to test early before a missed period because it would’ve made me more stressed and anxious if the result was negative. So as tempting as it was to test early, I waited for a missed period.
4. How do I use a pregnancy test?
Pregnancy tests are like urine ovulation tests: you either pee on a stick or dip the stick into a cup of urine and the result will say whether you’re pregnant or not pregnant. Each product may have specific instructions for use so read these carefully.
It’s best to test first thing in the morning when your urine is most concentrated, when it would have the highest possible level of hCG that day. Diluted urine from drinking a lot of water can make it more difficult to detect hCG and reduce the accuracy of tests.
5. What types of pregnancy tests are available?
Pregnancy tests can be purchased from the supermarket or chemist over-the-counter (i.e. without a prescription).
I will add a comparison table of different brands/products soon.
References
- Gnoth, C. & Johnson, S. (2014), Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments, Geburtshilfe Frauenheilkd, 74(7): 661-669. Accessed online: https://www.thieme-connect.com/products/ejournals/html/10.1055/s-0034-1368589#oTinW-hiddenTable2
- Therapeutic Goods Administration (2017). Pregnancy test kits [Webpage]. Accessed online: https://www.tga.gov.au/media-release/pregnancy-test-kits
