Q: My pregnancy test is negative. Could it be wrong?

A: This is a very important question for many women who perform pregnancy tests every day. The good news is that today's tests are extremely accurate. Pregnancy tests detect human chorionic gonadotropin (hCG) which is only produced by pregnancy cells. Today's tests can detect very small amounts of hCG in urine and blood. This allows women to detect pregnancy up to a week before a missed period. Physicians generally do not recommend performing a pregnancy test until after the expected period is missed. Twenty to 30 years ago, pregnancy tests were not positive until several weeks after a missed period. They were also more likely to detect substances other than hCG, giving a false positive result (when the woman is not pregnant). A false positive pregnancy test is very rare with today's tests. A false negative test (a negative pregnancy test when the woman is pregnant) is unusual and usually due to the test being performed incorrectly. Also, over-the-counter pregnancy tests are basically the same as the ones done in your doctor's office. So for this person, if her pregnancy test was negative, she was almost certainly not pregnant.

-- Dr. Mark A. Steele, Galen OB-Gyn; member, Chattanooga-Hamilton County Medical Society

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