Home pregnancy tests: Can you trust the results?

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Home pregnancy tests: Can you trust the results?

Home pregnancy tests are available without a prescription at most grocery stores and drugstores. Taking a home pregnancy test can be nerve-racking, though, especially if you're not sure whether 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 an accurate reading.

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 — or even before. For the most reliable results, however, wait until one week after a missed period.

Shortly after a fertilized egg attaches to your uterine lining, your body begins to produce a hormone called human chorionic gonadotropin (HCG). During early pregnancy, the level of HCG in your blood increases rapidly — often doubling every two days. Home pregnancy tests can reliably detect this hormone in your urine one week after a missed period. Days earlier, however, home pregnancy tests may not be as precise. If it's important to confirm your pregnancy right away, ask your health care provider about a blood test to detect HCG. The blood test — which can be done in your health care provider's office — is more sensitive than is the urine test.

Are there different types of home pregnancy tests?

Various types of home pregnancy tests are available. With most tests, you place the end of a dipstick in your urine stream or immerse the dipstick in a container of collected urine for five to 10 seconds. A few minutes later, the dipstick reveals the test result — often as a plus or minus sign, a line, a color change, or the words "pregnant" or "not pregnant" on a strip or window.

Keep in mind that instructions may vary from kit to kit. Read the instructions carefully before you take the test. If you have questions about how to take the test or interpret the results, contact the manufacturer. Look for a toll-free number or the manufacturer's website in the package instructions.

How accurate are home pregnancy tests?

Many home pregnancy tests claim to be 99 percent accurate on the day you miss your period. Although research suggests that most home pregnancy tests don't consistently spot pregnancy this early, home pregnancy tests are considered reliable when used according to package instructions one week after a missed period.

Could medications interfere with test results?

Fertility drugs or other medications that contain HCG may interfere with home pregnancy test results. But most medications — including antibiotics and birth control pills — don't affect the accuracy of home pregnancy tests.

Could a positive result be wrong?

Although rare, it's possible to get a positive result from a home pregnancy test when you're not actually pregnant. This is known as a false-positive. A false-positive may happen if you were recently pregnant or you take a pregnancy test too soon after taking a fertility drug that contains HCG. Ovarian cysts, ectopic pregnancy or menopause also may contribute to misleading test results.

Could a negative result be wrong?

It's possible to get a negative result from a home pregnancy test when you're actually pregnant. This is known as a false-negative — and it's much more likely to occur than is a false-positive. You may get a false-negative if you:

  • Take the test too early. Wait to take the test until your period is at least one day late. That's the earliest most home pregnancy tests can detect pregnancy. For the most accurate results, take the test one week after a missed period — when the level of HCG in your urine is most likely to be detectable.
  • Time the test wrong. Be sure to give the test time to work, but not too much time. Consider setting a timer according to the package instructions.
  • Use diluted urine. Drinking too much fluid before taking a home pregnancy test may cause a false-negative result. For the most accurate results, take the test first thing in the morning — when your urine is the most concentrated.

What happens next?

If your home pregnancy test is positive — or if you've taken a few home pregnancy tests and gotten mixed results — make an appointment with your health care provider. You may need a blood test or pelvic exam to confirm your pregnancy. The sooner your pregnancy is confirmed, the sooner you can begin prenatal care.

If your home pregnancy test is negative, repeat the test in a few days — especially if you took the test shortly after a missed period or your period is more than a week late. If you continue to get negative test results but your period doesn't begin, check with your health care provider. Many factors can lead to missed periods, including illness, stress, excessive exercise and hormonal imbalances. If you're not pregnant, your health care provider can help you get your menstrual cycle back on track.

Last Updated: 2010-10-30
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