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Home pregnancy tests: Can you trust the results?

Could you be pregnant? Here are the answers to common questions about home pregnancy tests.

By Mayo Clinic staff

Taking a home pregnancy test can be nerve-wracking, especially if you're not sure you can trust the results. Knowing when and how to take a home pregnancy test — as well as some of the pitfalls of home testing — can help ensure that your reading is accurate.

When should I take a home pregnancy test?

Many home pregnancy tests claim to be accurate as early as the first day of a missed period, but for the most reliable results, it's a good idea to wait until one week after a missed period. Home tests may not be as precise at the start of a pregnancy, and some women develop detectable amounts of pregnancy hormones later than others do. In addition, most manufacturers recommend retaking a home pregnancy test in a few days — a negative result shortly after your missed period doesn't necessarily mean that you're not pregnant.

Are there different types of home pregnancy tests?

Various types of home pregnancy tests are available, but most work in a similar way. Typically, you'll place the end of a dipstick in your urine stream or immerse the dipstick in a container of collected urine for five to ten seconds. A minute or two later, you'll see a plus or minus sign, a line, a color change, or the words "pregnant" or "not pregnant" on a strip or window on the dipstick. Some of these tests are more user-friendly and easier to read than others. If you have confusing results, you might want to try another brand.

With some tests, you'll mix a small amount of collected urine with a special liquid or powder. If the urine changes color, the test is positive.

Instructions may vary slightly from kit to kit. Read the instructions carefully before you take the test. If you have questions about how to do the test or interpret the results, call the manufacturer. Look for a toll-free number or the manufacturer's Web site in the package instructions.

How do home pregnancy tests detect pregnancy?

Shortly after a fertilized egg attaches to your uterine lining, your body begins to produce the hormone human chorionic gonadotropin (HCG). Home pregnancy tests — available without a prescription at most grocery stores and drugstores — can reliably detect this hormone in your urine one week after a missed period. Because the amount of HCG in your body increases rapidly during the first two weeks of pregnancy, home tests that detect the lowest level of the hormone produce the earliest confirmation of pregnancy. A more sensitive blood test to detect HCG can be done earlier in your doctor's office.

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References
  1. Am I pregnant? U.S. Department of Health and Human Services: Womenshealth.gov. http://www.womenshealth.gov/pregnancy/tryingtogetpregnant/amipregnant.cfm. Accessed Sept. 15, 2008.
  2. HCG. Lab Tests Online. http://www.labtestsonline.org/understanding/analytes/hcg/test.html. Accessed Sept. 15, 2008.
  3. Pregnancy tests. U.S. Department of Health and Human Services: Womenshealth.gov. http://www.4woman.gov/faq/pregtest.htm. Accessed Sept. 15, 2008.
  4. Cole LA, et al. Accuracy of home pregnancy tests at the time of missed menses. American Journal of Obstetrics and Gynecology. 2004;190(1):100-105.

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Nov. 1, 2008

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