Pregnancy testing

A pregnancy test checks your blood or urine for a hormone called human chorionic gonadotropin (hCG). This hormone is made by the placenta, which provides your growing baby with oxygen and nutrients from your bloodstream throughout the pregnancy. The amount of hCG in your blood and urine rises steeply during the first 12 weeks of pregnancy and then falls to low levels for the rest of the pregnancy.

Home pregnancy test kits#

Home pregnancy test kits are widely available from pharmacies. They offer accurate readings (up to 99 per cent) if used strictly according to the manufacturer’s instructions.

However, many women who use home test kits get inaccurate results. The most common mistake is to test too soon after a missed period. It is very important to follow the manufacturer’s instructions exactly, including the advice on when is the best time to use the kit.

Home test kits vary in how sensitive they are to hCG. Most are best used about one to two weeks after your period was due.

How to use a home pregnancy test kit#

Most home pregnancy tests follow the same basic principles:

• You collect urine in a small container and dip the test strip into it.
• Some kits instead offer a test strip that you hold under your stream of urine.

To improve accuracy, it is best to test your urine when you first get out of bed. Early morning urine is more concentrated and contains higher levels of hCG than at other times of the day.

Most test strips show the presence of hCG with a coloured line or dot. Results are usually rapid, taking only a few minutes. Most kits come with a second test strip, which allows you to test again at a later stage.

Positive result#

If the test is positive, no matter how faint the line, colour or sign is, you should see your doctor or a family planning clinic to confirm the result with a blood test or another urine test.

Be aware that false-positive results can happen, although they are rare. A false positive can occur if you have blood or protein in your urine. Certain drugs can also cause one, including tranquillisers, anticonvulsants, hypnotics and fertility drugs. Other reasons for a false-positive result include:

• a dirty urine collecting cup (detergent residue, for example, is known to cause false-positive results)
• a faulty test kit (for example, one that is damaged, past its use-by date, or has been exposed to heat or moisture)
• a recent birth or miscarriage, because the blood and urine may still contain detectable levels of hCG for a few weeks afterwards
• an ovarian tumour or some other type of hCG-producing growth

If you suspect you may be pregnant, see your doctor and ask for a blood pregnancy test to confirm the result.

Negative result#

If you get a negative result, you are probably not pregnant. However, false-negative results can happen if:

• you did not follow the instructions correctly
• the test is out of date
• you tested too soon after the pregnancy began
• your urine was too diluted

If a home pregnancy test gives a negative result yet you still feel that you are pregnant, trust your instincts. Treat yourself as if you are pregnant until proven otherwise, avoid cigarettes and alcohol, and make an appointment with your doctor for confirmation.

Pregnancy tests used by doctors#

Pregnancy tests performed in laboratories are about 99 per cent accurate.

Blood pregnancy tests#

Your doctor can give you a blood pregnancy test as early as 11 to 14 days after ovulation. To perform the test, the doctor draws blood from a vein in your arm and sends it to a laboratory. The results of most blood pregnancy tests take at least a couple of days, after which the laboratory advises the doctor of the result.

Blood test results are about 99 per cent accurate and can detect lower amounts of hCG than urine tests. One main type is the quantitative blood test, which measures the exact amount of hCG in the blood, although it cannot give an estimate of how far along the pregnancy is.

Urine pregnancy tests#

Your doctor can also give you a urine pregnancy test. You are asked to urinate into a plastic cup or similar container. The doctor then tests the urine using a kit that may look similar to a home pregnancy test kit.

Inaccurate results from tests given by the doctor#

Pregnancy tests taken by your doctor are rarely inaccurate. The occasional error is usually due to a mistake made in the laboratory. You can be reassured that a pregnancy test taken by your doctor is much more likely to be accurate than a home test you perform yourself.

Other reasons for a missed period#

Pregnancy is not the only reason for a missed period. Other possible reasons include:

• breastfeeding
• emotional stress
• severe weight loss
• severe dieting and exercising
• obesity
• particular drugs
• the onset of menopause

Key points#

• The most common mistake with home testing is to test too soon after a missed period.
• It is very important to follow the manufacturer’s instructions exactly.
• Certain drugs can cause a false-positive result, including tranquillisers, anticonvulsants, hypnotics and fertility drugs.
• A pregnancy test taken by your doctor is much more likely to be accurate than a home test, so see your doctor to confirm the result.

Where to get help#