Home Pregnancy Tests - Is a False Positive Possible?

By Debbi Carter

If you watch the TV show Bones, and saw the episode titled Proof in the Pudding, you may have wondered if it really is possible to get a false positive result on a home pregnancy test. The short answer is no, you can't get a false positive. The long answer starts with the word however. Learn exactly how a home pregnancy test works, and why you can't get a false positive.

A home pregnancy test, whether it is a strip, cassette, or stick test style all do one thing, it tests for a certain amount of hCG (human chorionic gonadotropin) which causes the dye in the window of the test marked with a T to change color. Human chorionic gonadotropin is only produced by a pregnant woman, so it is impossible to get a true false positive pregnancy test when you understand how the test works.

Here is where the answer gets a little more complicated with the word however coming into the fold. There are two times when you could get what appears to be a positive pregnancy test result, but not actually be pregnant. The first circumstance would be if you are undergoing infertility treatment that includes using an hCG trigger shot to induce ovulation. Women are told, or at least should be told, that she should not use a home pregnancy test for at least two weeks, or a full 14 days, after the trigger shot to be sure that there are no traces of the hCG trigger left in the system. If a women gets impatient and tests only 9 days after the trigger shot, it is fully possible that the home pregnancy test would have a positive result but that she may not actually be pregnant.

All home pregnancy tests come with directions that state the test results need to be read within a certain time frame, usually 3 to 5 minutes after completing the test.

If the test results are read after 5 to 10 minutes an evaporation line might be seen, and can by interpreted as a positive result instead of what it really is.

So ladies, the next time you take a home pregnancy test be sure to read all of the directions of the test, make sure that if you did use an hCG trigger shot, that enough time has passed and by all means, don't dig the test out of the trash to "double check" the results. If you get a positive result within the tests time frame, congratulations, you are pregnant.

Debbi Carter has been researching, advising, and studying infertility causes and treatments as well as preconception issues for over 10 years now.

Debbi has developed and maintained TTC Dreams, a website about preconception and infertility since 1999, and continues to expand her knowledge and understanding of infertility. She is also the owner of the Trying To Conceive support group on Yahoo Groups.

Debbi also offers a free online course about infertility allowing you to learn about the basics from the comfort of your home at your computer. You can read her course Introduction to Infertility at your own pace and contact her through the course for additional information too.