How accurate are pregnancy tests?

baby
© Mariusz Blach ()
Performing Pregnancy Tests
Hormones

During early pregnancy, the body produces a pregnancy hormone known as human chorionic gonadotrophin (HCG) and it is this hormone that forms the basis of pregnancy tests.

The hormone is released into the urine in large quantities and pregnancy kits seek to detect this. When it comes to performing a home pregnancy test, it is essential to carefully read the instructions before use.

Note: Not all pregnancy tests work in the same way so if you have used a Clearblue test in the past, you may find that a different brand works in a different way.

When to perform the test

You can use a pregnancy test from the first day of a missed period. You may be required to perform the test at a specific time of day so do check the instructions before use.

Refrain from drinking large quantities of liquids before performing a test as this can produce a negative result.
Medications and Pregnancy Tests
Certain medications can affect the reliability of pregnancy tests. These include:
Medicines used in the treatment of Parkinson’s disease;
Sleeping tablets;
tranquillisers;
Medicines used in the treatment of infertility;
Promethazine, which is used to treat allergies;
Diuretics, which are used to increase urine production;
Anti-convulsants, which are used to prevent seizures.
The patient information leaflet which accompanies a pregnancy kit will provide more information on the medicines which affect pregnancy test results.
Positive Pregnancy Test Results
If you receive a positive pregnancy test result, it is advisable to consult with your general practitioner. They may or may not repeat the test. Your general practitioner will provide further advice and will refer you to a specialist, whether you wish to continue with your pregnancy or not.
Negative Pregnancy Test Results
If your pregnancy test result shows up negative, this is not to say that you are not pregnant. Negative test results cannot be relied upon as highly as positive test results.

If you perform a pregnancy test early on, you may be pregnant but not producing enough HCG to provide a positive result. If you consider yourself to be pregnant yet receive a negative test result, try again after one week, or consult with your general practitioner.