Our guide to pregnancy tests

We know how difficult it can be to choose the pregnancy test that’s just right for you. So, to help you to decide, we’ve produced this guide that supports you to understand a little more about how they work and what the difference is between the different pregnancy tests.

 

How do pregnancy tests work?

Pregnancy tests work by detecting a hormone called human chorionic gonadotrophin (hCG), also known as the “pregnancy hormone”, in your urine. When your egg is fertilised and becomes an embryo, the cells surrounding the embryo start to produce hCG. This is important because it signals to the body to start preparing for a pregnancy instead of continuing towards the start of another period. Pregnancy tests work by detecting hCG in your urine.

 

Are pregnancy tests accurate?

The accuracy of a pregnancy test depends on how well it can detect lower levels of hCG at the very early stages of your pregnancy. The level of hCG starts off low but then increases very quickly, doubling every 2-3 days. By the time your period would normally have been due, hCG will have increased to a high enough level that most pregnancy tests will be able to detect it very accurately, typically to around 99% accuracy. This is the best time to take a pregnancy test if the most important thing for you is how accurate the result is.

Some pregnancy tests are sensitive to lower levels of hCG and can therefore be used earlier than this. If you do test earlier, the result may be less accurate. We know that when you are trying for a baby you may really want to know as soon as possible. For this reason, it can be a good idea to follow up with a second test at the time your period would normally be due.

Another useful feature of a new type of pregnancy test kit, is to show you how many weeks it has been since you conceived. The level of hCG in early pregnancy is known to increase evenly so can be used to test this, although there can be some variation between women.

Whilst pregnancy tests are now very accurate, there are some basic things to remember to get the best from them. Always buy your pregnancy tests from a reputable supplier. All pregnancy tests sold by Dr Fertility carry a CE mark to show they comply with EU health, safety and environmental requirements. Always store your pregnancy tests in a cool, dry environment, as shown on the packaging. Always use pregnancy tests within their expiry date. Read the manufacturer’s instructions carefully and use the pregnancy test exactly as described.

 

What are false positives and false negatives?

Pregnancy tests which can be used much earlier are great when you are struggling to wait until your period is due. If you do test early and get a negative result, this might sometimes be because the level of hCG is not quite high enough for even these sensitive tests to detect. If you do still think you might be pregnant, it would be a good idea to do a follow up test on the day your period is due.

Sometimes you can get a positive test result and find out later that you are not pregnant. This doesn’t mean that the original test was wrong. Unfortunately, it is possibly due to a natural loss of the pregnancy which can occur in the early stages. If you do get unexpected results you should check these with your doctor.

There may be other situations when you might get a false positive. Fertility drugs containing hCG can lead to misleading results (these fertility drugs are usually given by injection and testing too soon after administration may give a false ‘Pregnant’ result). If you have recently been pregnant (even if you did not carry to full term) you may get a false ‘Pregnant’ result. Ectopic pregnancy (when a fertilised egg implants itself outside of the womb, usually in one of the fallopian tubes), ovarian cysts, menopause and some very rare medical conditions can lead to misleading results. If you do get unexpected results you should discuss them with your doctor.

When carrying out a pregnancy test, do make sure to check the control window, which confirms that the test has completed properly. If the control window does not show the test has completed properly, then any result would not be valid, and a new test should be carried out.

 

What do different pregnancy tests offer?

To help make things easier, we’ve provided a breakdown of all the pregnancy tests we offer with the key features of each one.

The main features you might be thinking about include:
  • How early can I use the test?
  • How accurate is the test?
  • How quickly will the result show after using the test?
  • Does it have a digital result? – This takes the guesswork out of whether a faint line is positive or not
  • What else can it tell me? – Some tests can even tell you how far along you are after conception

Deciding which pregnancy test is right for you is all down to personal choice. We do find, however, that many of our customers use more than one type of test to get the best out of each of the features, such as testing as early as possible and then following up with another test that confirms the first result and also tells you how far along you are.

The table below outlines all of the main features. To learn even more about each pregnancy test, visit the product page for that particular test.

Test What’s inside How early can I test? * Accuracy Time to get results
Clearblue Rapid Detection Pregnancy Test Available in packs of 2 or 5 tests On the day your period is due • > 99% from the day your period is due
    1 minute
    Clearblue Early Detection Pregnancy Test Available in a pack of 2 tests 5 days before your period is due

    • > 99% up to 3 days before your period is due

    • 79% 5 days before your period is due

      3 minutes
      Clearblue Digital Early Detection Pregnancy Test Available in a pack of 2 tests 4 days before your period is due

      • 99% from the day your period is due

      • 51% 4 days before your period is due

        3 minutes Displayed digitally as ‘Pregnant’ or ‘Not Pregnant’
        Clearblue Digital weeks Indicator Pregnancy Test Available in a pack of 2 tests 4 days before your period is due

        • > 99% from the day your period is due

        • 65% 4 days before your period is due

        • 93% accurate at showing you how far along you are

          3 minutes Displayed digitally as ‘Pregnant’ or ‘Not Pregnant’ AND how far along you are in weeks
          Clearblue Combo Pack Triple Check Pregnancy Test Available as a combo pack:

          2 x Early Detection Pregnancy Tests

          and

          1 x Digital Early Detection Pregnancy Test
          5 days before your period is due

          • > 99% up to 3 days before your period is due

          • 79% 5 days before your period is due

            3 minutes
            4 days before your period is due

            • 99% from the day your period is due

            • 51% 4 days before your period is due

              3 minutes
              Displayed digitally as ‘Pregnant’ or ‘Not Pregnant’
              Clearblue Combo Pack Double-Check and Date Available as a combo pack:

              1 x Rapid Detection Pregnancy test

              and

              1 x Digital weeks Indicator Pregnancy Test
              On the day your period is due • > 99% from the day your period is due


                1 minute
                4 days before your period is due

                • > 99% from the day your period is due

                • 65% 4 days before period due

                • 93% accurate at showing you how far along you are

                  3 minutes
                  Use as a follow-up to confirm your pregnancy AND how far along you are, in a clear digital display
                  Clearblue Trying for a Baby Kit Available as a kit:

                  1 x Rapid Detection Pregnancy Test

                  (and 10 x Clearblue Digital Advanced Dual Hormone Ovulation Tests)
                  On the day your period is due • > 99% from the day your period is due
                    1 minute
                    Comes as part of an ovulation test kit that first tests for 4 or more fertile days per cycle before using the pregnancy test
                    First Response Early Result Pregnancy Test Available as a pack of 2 tests 5 days before your period is due • > 99% up to 3 days before period due
                    76% 5 days before period due

                      3 minutes

                      BabyStart Early Detection Pregnancy Test Available as a pack of 2 tests 10 days after conception
                      • 99% from the day your period is due
                      Reduced accuracy if used before this

                        5 minutes

                         

                        *This the number of days before your period is due that you can test. This is sometimes also expressed as the number of days before your missed period. The day of your missed period is 1 day after your period is due. For example, 6 days before your missed period is the same as 5 days before your period is due.

                        The information presented here is a summary of the information that is available on each product page. For full information about each product, please see the product descriptions available on the product page.

                        References

                        1. Human chorionic gonadotrophin, You and your hormones, Society for endocrinology [Online content accessed 24.04.2020] https://www.yourhormones.info/hormones/human-chorionic-gonadotrophin/
                        2. Larsen, J. Buchanan, P. et al. International Journal of Gynaecology and Obstetrics 123 (2013) 189–195. Human chorionic gonadotropin as a measure of pregnancy duration https://www.sciencedirect.com/science/article/pii/S0020729213004232
                        3. GOV UK – CE Marking [Online content accessed 27.04.2020] https://www.gov.uk/guidance/ce-marking
                        4. NHS Health A-Z: Ectopic pregnancy [Online content accessed 27/04/2020] https://www.nhs.uk/conditions/ectopic-pregnancy/ All other references are available on the original product pages

                         

                        Written on 28.04.20 Reviewed by 28.04.23