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Reasons for False Positive Pregnancy Test

Most women take the home pregnancy test to know if they are pregnant or not. But how accurate are they? Can you have a false positive pregnancy detected? Although very unusual, there are several reasons to why you may get a "false positive".
HerHaleness Staff
Last Updated: Jun 21, 2018
HPT (home pregnancy tests) are opted by many women, as they are easy, comfortable and very quick. But, the truth is, that these tests are only about 97% accurate.
Pregnancy test
So, is a false positive pregnancy possible? Indeed yes, but in very rare cases. As these sticks are not hundred percent accurate, there are thin chances of getting a wrong result. However, there are many other reasons that result in a false positive pregnancy.
Reasons for False Positive Pregnancy
Contamination
The urine sample is said to be contaminated, if it gets mixed with any other substance; for example, soap, detergent, creams, etc. This can either be present in the sample or the sample container. This can show a false positive result. In order to avoid this, take a test in which you have to urinate directly on the strip or see a doctor for a blood test.
hCG (Human Chorionic Gonadotropin) Content
Home pregnancy tests detect a pregnancy by the presence of the Human Chorionic Gonadotropin (hCG) hormone - a glycoprotein hormone that is produced in a woman's urine by the placenta, after fertilization takes place.
The hCG hormone is present in very small and sometimes undetectable amounts in the urine, during the initial stages of the pregnancy, so if you are using a home pregnancy test kit to find out if you are pregnant, you should preferably carry out the test at least 8 days after conception or after you've missed a period.
The hCG hormone can also be produced in case of stomach tumor, cysts, polycystic ovary, bladder cancer, etc. Due to the presence of this hormone, the woman might feel nauseated and bloated.
But, in this case, the feeling of nausea has nothing to do with morning sickness, nor has the bloating anything to do with pregnancy. A few pregnancy sticks are very sensitive, hence they determine even very small amounts of hCG, resulting in a false positive.
Wrong Fluids
Sometimes, women test alternative fluids like blood, breast milk, saliva, serum, etc., instead of urine. These alternative fluids have different hormones present in them. Hence, the usage of wrong fluids for the test will eventuate wrong results.
Wrong Timing
Pregnancy is detected by the presence of the hCG hormone, and it is present in very low levels during the initial stages of pregnancy. So, if you test too early, the test may fail to detect by giving out wrong result. The hCG hormone can sometimes be produced by tissues other than the placenta, and so a woman who is not pregnant may get a positive result.
It's advisable to wait at least eight days before taking a pregnancy test. Test the first urine of the day, as this has hCG in concentrated amounts, or you can get a test done every two days. If you are pregnant, the hCG level will show a steady increase.
Improper Testing
Home pregnancy tests have a 10 minute limit within which, the results should be checked. After 10 minutes, the stick must be discarded. Many a time, the stick changes color after 10 minutes, which leaves people confused, or even misguides them.
After the first 10 minutes, the results are considered wrong or invalid. It is also necessary to read the 'how-to-use' instructions carefully when using a home pregnancy test kit.
Evaporation Line
Every pregnancy test stick has two lines on it. One line turns pink when it is exposed to any kind of moisture, while the other line will turn pink only when it is exposed to moisture containing hCG.
When exposed to moisture the first line turns dark pink, while the second line will be faint pink in color. If the color of the second line is not as dark as the first line, your test result is negative. Most women confuse this faint second line for a positive result.
Chemical Pregnancy
In early pregnancy, before the confirmation of the heartbeat, the chances of a miscarriage is about 15%. It later drops down to 5%, once the heartbeat is detected. This early miscarriage is called a Chemical Pregnancy. Many women become pregnant and then suffer a miscarriage.
According to research, this seems to be a common phenomenon with many first-time pregnancies. So, a woman may get a positive result from her home pregnancy test and later think it was a false positive when she starts bleeding.
But, the real reason is that the embryo secrets the hCG hormone which decreases after the miscarriage. The level of hCG will decrease in the blood, but still be present in the urine for a while. Such conditions are very favorable for a false pregnancy result.
Influence of Medication
If you are on any medication that contains the hCG hormone, it will affect your pregnancy test and give out a false result. Especially women, who are undergoing infertility treatments, should keep this in mind. So, it is important to talk to your doctor both before, and after you do a home pregnancy test.
Menopause
After menopause, women have a certain amount of hCG present in their urine. This very small amount of hCG is usually very difficult to be detected in the test. However, some pregnancy sticks are very sensitive. In such cases, a false positive can be detected by these sensitive sticks.
Defective Test Kit
Before buying a home pregnancy test kit, remember to check the expiry date on the pack. You won't get correct test results from a pack that is expired. There is also a chance that the test kit may be a defective one, which is another reason for a false positive.
If you think you have made a mistake in the testing, you should get another pregnancy test done after two or more days. Don't depend wholly on the home pregnancy test kit results. Visit your doctor and have a blood test for pregnancy done. This is much more accurate.
Disclaimer: This is for informative purposes only, and should not be used as a replacement for expert medical advice.