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

Home Pregnancy Tests

HCG pregnancy tests or home pregnancy tests determine pregnancy through the detection of the hormone Human Chorionic Gonadotropin (hCG) in a woman’s urine. Doctors recommend that you wait until you have missed a period to take a home pregnancy test. If you can not wait that long to find out and you know the day you may have conceived, then the earliest you can take a test would be 14 days from possible conception. Home tests are usually 97% accurate when all instructions are followed correctly and the results are read on time. Some kits come with two tests so that in case you have made a mistake, you may take the home pregnancy tests gain.

False Positive Pregnancy Test Results and What Causes Them

A false positive pregnancy test is when the test says that you are pregnant but actually you are not. This is a one off case and a positive pregnancy test is a pretty good indication that you are pregnant. False positive pregnancy tests are rare - though there are instances and conditions where they can occur.

There could be various reasons for a false positive test.

Chemical Pregnancy
A chemical pregnancy is basically an early miscarriage. Research has shown that half of all first pregnancies end in miscarriage. Due to the high sensitivity of home pregnancy tests, many women catch early pregnancies but end up going on to have their periods due to a chemical pregnancy.

Missed Reaction Time
For accuracy in home pregnancy tests it is essential that you read the test results in the stipulated reaction time. If you let the test sit for too long (after the instructions on the box tell you), the test is invalid. This may cause it to show false positive results.

Chemical Interference
Drugs that have the pregnancy hormone Human Chorionic Gonadotropin (hCG) in them can cause incorrect results in home pregnancy tests. The Human Chorionic Gonadotropin (hCG) in them may be responsible for the false positive pregnancy test. If you have had an HCG shot due to infertilty treatments, you need to be sure the shot is out of your system before you attempt to use early pregnancy tests.

Evaporation Lines
While technically not a true pregnancy, some pregnancy tests leave a faint evaporation line as the urine crosses the test. This faint very light grey evaporation line in the test area is often interpretted as a positive result.

AimStrip pregnancy test strips have a very good reputation of NOT leaving evaporation lines and are much less expensive than brands you can buy in your local supermarket or drug store.

If you are not sure about your home pregnancy results it is recommended that you try again after a couple of days. If doubts regarding the results still persist, you must see a doctor for a pregnancy blood test. A blood test administered by your doctor is more sensitive than the early home tests and can be taken between seven and twelve days after you conceive.

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  • The information provided here should not be considered medical advice. It is based on the average experience of women trying to conceive and may not be what you may be experiencing. It's not meant to be a replacement for any advice you may receive from your doctor. If you have any concerns about your cycle or our ability to get pregnant, we advise you to contact your doctor.