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Written by Caroline Meyer

False negatives are very common in early pregnancy when the hormone levels may not yet be high enough to detect in urine samples, but what is a false positive? 

Sometimes a home pregnancy test will show a positive, when in fact you are not pregnant.  You may do the test and then two or three days later you have a normal period. A blood test, which is a better indicator, will show that there are no pregnancy hormones showing up in your blood. This can be sad and frustrating, especially if you are trying to conceive. It can also be quite shocking when you are not wanting to get pregnant to get a false positive, even though the later result may be a relief. 

While most home pregnancy tests are quite accurate, they still have around a 3% error margin. That means out of every 100 home pregnancy tests done, 3 will show as inconclusive or as a false positive or false negative. A false negative is a lot more common than a false positive though. A blood test is always recommended to make sure that you are pregnant. 

The home pregnancy test checks for the hCG hormone (human chorionic gonadotropin) in the urine sample. When you are pregnant your body will start producing the hormone as soon as the egg has implanted on to the uterine wall. These cells become the placenta eventually and this is where the secretion of hCG comes from.  If you take the test and show positive but start your period shortly afterwards, you are not likely to be pregnant. Even when you are not pregnant, you do secrete a small amount of hCG but this is usually far lower than can be detected by a home pregnancy test. 

A false positive can be due to using the test incorrectly and not following the manufacturer’s instructions as given. You also need to ensure that the cup used to collect the urine is completely sterile unless it is a midstream stick test, which just needs to be dipped in, mid-flow. Even cleaning product residue in the collection container can cause the test to give an incorrect result. You also need to ensure that the test is left for the right amount of time before checking the result. Too early can show a false negative and too long can give a false positive. After a long period, you may see a faint evaporation line which could wrongly be assessed as a positive pregnancy result. 

During the time period the result is pending, the test should not be left in areas of high or low humidity or in an area which is hot or cold. Too high temps or large fluctuations in moisture can also cause incorrect readings. Check the instruction manual on how to collect the urine, the best conditions for an accurate result and how long to wait. 

If you are on medication or hormone treatments that contain hCG you may also experience a false positive. Many fertility drugs contain hCG and can cause a false reading on the pregnancy test. Certain anxiety medications such as Xanax and Valium may also result in an incorrect positive reading on the pregnancy test. Diuretics, anticonvulsants and antipsychotics can also affect the test. Parkinson’s disease medication is also known to give a false reading. 

One of the other reasons you may experience a false positive is if you use an expired test. Check the box for an expiry before using as it is potentially less effective after the printed expiry date. Many people buy more than one kit or even a bulk lot, especially when they are trying to conceive. They may use one or two and the rest are probably not discarded and may stay in the cupboard for a long period of time. Using these older test packs may mean that the readings are not accurate and could result in a false positive. 

Recent termination of pregnancy, a recent birth or a miscarriage may result in there still being hCG in your body which can be the result of a false positive reading. It is recommended that you wait sometime after experiencing any of the above to allow for the hCG levels to drop off before doing a home pregnancy test. The tests can possibly pick up low levels of hCG even weeks afterwards as they are usually quite sensitive to the hormone.  

High protein levels in the urine can also create a situation that leads to a false positive reading in a home pregnancy test. This is usually due to medical conditions such as kidney disease, ovarian issues such as cysts, tumours or cancer or problems with your pituitary gland.  In very rare cases, an ectopic pregnancy can occur. This is when the egg implants outside of the uterus or does not exit the fallopian tube properly. Your body will produce hCG even though the pregnancy is not viable and cannot be carried to term. 

A false reading on a home pregnancy test is fairly uncommon and it is always recommended that you get a blood test to confirm the suspected pregnancy. A false positive can cause mental anguish, especially in people that are struggling to conceive. If you feel you need help, speak to your doctor about support groups or therapy to help you overcome the pain you may be feeling. They may also recommend medication if it necessary.

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