Home Pregnancy Tests

How do home pregnancy tests work?

Home pregnancy tests measure the presence of a hormone in your urine called human chorionic gonadotropin (hCG). This hormone is produced by cells from the placenta and enters your bloodstream when the fertilized egg implants in your uterus. The amount of hCG in your body then increases rapidly over the next few weeks. Fourteen days after fertilization, about the time you would expect your period, some home pregnancy tests may be able to detect the hormone in your urine and give you a positive result. However, most home pregnancy kits are not sensitive enough to guarantee you an accurate result until a week after your expected period.

How accurate are they on the day you miss your period?

Most home pregnancy tests claim "greater than 99 percent accurate" and imply that you can use them as early as the day you miss your period. A study published in 2004 in the American Journal of Obstetrics and Gynecology has shown that this is misleading. The amount of hCG in the urine on any given day after implantation can vary. If you suspect that you are pregnant, we recommend that you follow up your home pregnancy test with a test at your GP.

How do I use a home pregnancy kit?

• check the expiration date on the test and make sure it's still valid
• read the directions carefully  they can vary with different brands
• follow the instructions and wait for the results

The tests also vary in the way that they display results. Some show pink or blue lines on the test strip, while others reveal a red plus or minus sign in a window. Most have a control indicator (often a second line or symbol) that indicates whether the test is valid. If the control indicator doesn't show up properly, the test may be faulty.

What happens if the result is negative?

If the test shows a negative result, wait another few days or a week before trying again. For best results, try taking the test first thing in the morning, when your urine is most concentrated. One negative result means doesn’t mean you're not pregnant

What is a false positive result?

A false positive result means that the test tells you that you are pregnant but you are not. If you get a positive result and then get your period soon after, you may have had what's called a "chemical pregnancy." A chemical pregnancy occurs when a fertilized egg implants in your uterus and starts producing hCG but then stops developing for some reason. This happens with about a third to a half of all fertilized eggs because they're abnormal or incapable of developing into and surviving as an embryo. If this is the case, you'll go on to get your period though it may be a little heavier and a few days later than usual.

Where can I buy a home pregnancy test?

You can buy a home pregnancy test without a prescription at most chemists for a few pounds.