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Pregnancy Tests & False Positives

As you nervously eye the timer, waiting for your pregnancy test results, questions are bound to swirl through your mind. The last one you'll want to consider is whether you can trust a positive test. Getting a positive result when you're not truly pregnant is possible both from home tests and those performed at your doctor's office, but it's unlikely for the typical woman.

Feeling Positive About a Positive Result

If you're hoping for a positive result and get it, don't feel burdened by worry that it's inaccurate. Home pregnancy tests are about 97 percent accurate, says the American Pregnancy Association. These tests are much more likely to show false negatives than false positives. A pregnant woman might get a negative result if she takes the test too early or if her urine is diluted from drinking too much fluid, says MayoClinic.org.

How a Test Works

The home pregnancy tests detect human chorionic gonadotropin, or HCG, in urine. The body begins producing HCG once an embryo attaches to the wall of the uterus. A urine or blood test performed at a doctor's office can also detect HCG. A blood test can reveal HCG about 11 days after conception, says the APA, while a urine test can accurately detect it about 12 to 14 days after conception. In her book "Conception, Pregnancy & Birth: The Childbirth Bible for Today's Parents," Dr. Miriam Stoppard recommends taking a pregnancy test around the time of your first missed period.

RELATED: Types of Pregnancy Tests

Causes of False Positives

Typically a false positive is caused by one of two things. Either there was an error in testing, or the HCG is caused by something other than pregnancy. A defective test or human error in following the test directions could lead to a hard-to-read result or blatant false positive. A false positive may also occur if you were briefly pregnant but no longer are, or if you've recently taken certain fertility drugs. Hormone drugs or the beginning of menopause may affect HCG levels. Other medications, including antibiotics and pain medications, shouldn't affect your test's accuracy, Stoppard writes. Ovarian cancer can also cause a positive HCG test.

Following Up

If you don't trust the home pregnancy test—say, one of the two lines that means it's positive looks blurry or faint—it doesn't hurt to try again. Stoppard recommends repeating the test a few days later. Make an appointment with your doctor if your results are still positive. If you have any doubts about the validity of your test, like if you haven't had unprotected sex recently or are beginning to experience signs of menopause, raise them with the doctor. A doctor can perform further tests to verify whether or not you need to stock up on diapers.

RELATED: Pregnancy Tests Throughout History

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