How Common Is A False Positive Pregnancy Test And What Causes It?

Home Pregnancy Tests

The best way to get accurate results when using a home pregnancy test is to wait until your period late. At that time, the level of hCG in your sytem will be large enough that all of the pregnancy tests on the market will be able to detect it, producing a positive pregnancy test result.

Most women, who are trying to get pregnant, prefer to find out as soon as possible. That “two week wait” becomes unbearable. There are many home pregnancy tests on the market that claim you can test much earlier, usually 4 or 5 days before your period is due. These early test pregnancy tests are typically about 97% accurate, when all the instructions are follow exactly and you read the results within the time frame listed in the instructions.

What Can Cause False Positive Pregnancy Test Results?

A truly “false positive” test result, due to a faulty home pregnancy test is fairly rare. A positive result which is not repeatable, with subsequent home pregnancy tests, is usually because of one of these reasons: Chemical pregnancy, missed reaction time, chemical interference or an evaporation line on the pregnancy test.

Chemical Pregnancy

As unfortunate as it is, about 25% of all pregnancies end up being a chemical pregnancy, also known as an early miscarriage. A chemical pregnancy happens when a pregnancy is lost shortly after implantation. With the advancement in sensitivity of the home pregnancy tests on the market today, women are able to detect pregnancy in the very, very early stages. This is the downside of the super sensitive pregnancy tests – the joy of discovering pregnancy very early on, followed by crushing heartbreak if an early miscarrige occurs.

Missed Reaction Time

You really need to follow the instructions included with your home pregnancy test exactly. The manufacturer lets you know how long you should allow the test to sit before interpreting the results. If you let the test sit for longer than the instructions state, any results you interpret need to be considered invalid. Reading after the recommended time frame has passed can show results that you will misinterpret as a positive result.

Chemical Interference

If you are undergoing fertility treatments and have had a hCG (Human Chorionic Gonadotropin) trigger shot, you will need to make sure the shot has had enough time to metabolize through and clear your system. Fertility doctors suggest waiting about 14 days for your system to be clear of the hCG before taking a pregnancy test. Testing before this time may very well likely produce a positive result when you are not truly pregnant.

Evaporation Lines

Some pregnancy tests can leave an evaporation line on the pregnancy test, as the urine crosses the result area. The evaporation line is usually a very faint, grayish line in the results area of the pregnancy test. The color of the line is not what the test instructions say should be there, for a positive result, but many women, will erroneously interpret the line as a positive result.

If you feel you are having early pregnancy symptoms and not getting the results you think you should be from your home pregnancy tests, you should contact your doctor for a blood pregnancy test.

  • PrayinMama

    Not nessecerily no… You could have been pregnant but had a miscarriage things like that you need to see a doctor

  • H

    My last period started on May 23rd, 2014 and I haven’t had one since! I took a test today, and it was a positive! My boyfriend and I are very, very excited!
    However, the only thing that I am worried about is my existing health issues… I have a prolactin secreting pituitary brain tumor. I was diagnosed with it last year. I just hope that it doesn’t effect my pregnancy!

Last modified: February 14, 2014