Home pregnancy tests can detect the presence of a female hormone (called human chorionic gonadotropin, hCG) in a sample of urine. High levels of hCG are produced during pregnancy. The home tests are very similar to the pregnancy tests done on urine in most doctors' offices.

When a woman gets pregnant, the egg usually becomes fertilized by a sperm cell in a fallopian tube (conception). Within 9 days after fertilization, the egg moves down the fallopian tube into the uterus and attaches (implants) to the wall of the uterus. Once the fertilized egg implants, the placenta starts to develop and begins to release hCG into the mother's blood. Some of this hCG also gets passed in her urine. In the first few weeks of pregnancy, the amount of hCG in the urine rises rapidly, doubling every 2 to 3 days.

There are three basic types of home pregnancy tests:

• The most common types of home pregnancy tests use a test strip or dipstick that you either hold in the urine stream or dip into a sample of urine. An area on the end of the dipstick or test strip changes color if hCG is present, meaning you are pregnant. Name brands of these pregnancy tests include Advance, Clear Blue Easy, Confirm, and EPT.
• A second type uses a urine collection cup or well with a testing device. To use this type of test, you place several drops of urine into a well in the testing device, or you immerse the well into urine that has been collected in a cup. An area of the device changes color if hCG is present, meaning you are pregnant. Name brands for these tests include Be Sure, Fact Plus, and Precise.
• A third, less common type of test involves mixing a sample of urine in several tubes or cups with a powder or liquid to produce a chemical reaction. The presence of hCG causes a chemical reaction that produces a color change. The color of the resulting mixture is then compared against a color comparison strip. Name brands of this kind of test include Answer Plus and the Q test.

A first morning urine sample (that has accumulated in the bladder overnight) will provide the most accurate test results.

The accuracy of home pregnancy tests vary. If used correctly, the best tests can detect hCG as early as the first day of a missed menstrual period (about 14 days after conception).

Home Pregnancy Tests
Results

If you are pregnant, most tests usually produce a color change or the appearance of a symbol in the indicator area of the test strip or on the part of the device in contact with the urine.