Female hormones stimulate the reproductive cycle, causing the growth and release of eggs for fertilisation by sperm. When an egg is fertilised, a hormone called human chorionic gonadotrophin (HCG) is produced and can be measured in the urine of a pregnant woman from about the first day of a missed period.
Home pregnancy tests are sensitive enough to provide a reading that is about 99 per cent accurate, if instructions are followed correctly.
Home pregnancy tests that are currently available include Clearblue One Step, Clearview HGC, Crystal Clear, Discover, Dotest Confirm, First Response, Fortel and Pregnosis.
Pregnancy testing can be carried out in 2 ways: some test sticks are held in mid-stream urine, others need a urine sample which is tested with a dip-and-read stick.
If using a dip-and-read product, make sure that the urine is collected in a clean glass or plastic container. Urine samples should be tested immediately after collection.
HCG is often at its strongest concentration first thing in the morning, so this is a good time to take the test.
Alcohol, pain killers, antibiotics and oral contraceptives should not affect the pregnancy tests. However some medicines, such as fertility medicines, cause false-positive pregnancy test results. Traces of HCG hormone may also be found in urine for up to 8 weeks after a miscarriage or termination and for up to 4 weeks after the birth of a child.
If the test result is positive, assume you are pregnant and see your doctor as soon as possible. If the test is negative despite a missed period, check that you followed the instructions correctly and repeat the test according to the manufacturer’s instructions. If the second test is negative and menstruation has not started, seek advice from your doctor.
Last Reviewed: 21 October 2009