A pregnancy test checks your blood or urine for a hormone called human chorionic gonadotropin (hCG). This is a hormone made by the placenta (the placenta provides your growing baby with oxygen and nutrients from your bloodstream throughout the pregnancy). The amount of hCG in your blood and urine rise steeply during the first 12 weeks of pregnancy and then fall to low levels for the rest of the pregnancy.
Home pregnancy test kits are available from pharmacists. These kits offer accurate readings (up to 99 per cent) if performed strictly according to the manufacturer’s instructions. However, many women who use home pregnancy test kits get inaccurate results.
The most common mistake is to test for pregnancy too soon after the missed period. The manufacturer’s instructions will tell you when is the best time to use the kit. It is very important to follow the manufacturer’s instructions exactly.
Home pregnancy test kits vary in their sensitivity to hCG. Most test kits are best used about one to two weeks after your period was due. Always strictly follow the manufacturer’s instructions. Generally speaking, most home pregnancy tests follow the same basic principles:
If the test is positive (no matter how faint the line, colour or sign is), you should see your GP (doctor) (or family planning clinic) to confirm the result with a blood test or another urine test. Be aware that false-positive and false-negative results can happen.
False positive: Although rare, this can happen if you have blood or protein in your urine. Certain drugs can also cause this (tranquilisers, anticonvulsants, hypnotics and fertility drugs). Other reasons for false results are:
If you get a negative result, you are probably not pregnant BUT false-negatives can happen if:
If you suspect you may be pregnant, see your doctor and ask for a blood pregnancy test to confirm the result.
If a home pregnancy test gives a negative result, yet you feel that you are pregnant:
Your doctor can give you a blood pregnancy test as early as 11 to 14 days after ovulation. To perform a blood pregnancy test, the doctor draws blood from a vein in your arm. This blood is sent to a laboratory for testing. The results of most blood pregnancy tests take at least a couple of days. The laboratory then advises the doctor of the result.
Blood test results are about 99 per cent accurate and can detect lower amounts of hCG than urine pregnancy tests. The two main types of blood pregnancy test include:
The doctor can give you a urine pregnancy test. You are asked to urinate into a plastic cup or something similar. The doctor then tests the urine using a kit that may look similar to a home pregnancy test kit.
Pregnancy tests taken by your doctor are rarely inaccurate. The occasional error is usually due to mistakes made in the laboratory. However, you can be reassured that the pregnancy test taken by your doctor is much more likely to be accurate than a home test you perform yourself.