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False pregnancy test

Most pregnancy tests (home pregnancy tests) determine pregnancy through the detection of the hormone Human Chorionic Gonadotropin (hCG) in a woman’s urine. Human Chorionic Gonadotropin (hCG) is a hormone which is produced early in pregnancy by the placenta in great volume (hormone released by developing embryos). HCG detection in the urine and serum is the basis for most of pregnancy tests. Normally most variants of the home pregnancy test cannot be considered accurate until taken on the date or a few days after a missed period.

It is strongly recommended that you wait until you have missed a period to take a home pregnancy test. If you cannot 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%-99% 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 again.

Sometimes home pregnancy test can yield false positive results for several reasons. Even a pregnancy test performed on blood can show a false positive under certain circumstances. In most cases we could have false negative pregnancy test. False positive pregnancy tests are rare, but they do occur.

Can you be not pregnant if the pregnancy test is positive?

The answer is – YES, it is possible. There are several reasons why your pregnancy test can be positive even if you are not pregnant.

Main Causes for False Positive Pregnancy Test

Pregnancy test

Pregnancy test

  • Soap or detergents are pretty common corrupting agent to the pregnancy test. Urine collection should be done carefully to avoid such exposure – don’t use soap or any detergents before making your pregnancy test.
    Many pregnancy tests request urination directly on the stick used to give results. If pregnancy test requested urination in the special cup, the cup should be very clean and presumably free of any leftover soap or any detergents.
  • Missed test 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 stay for too long (more than instruction on the box), the test is invalid. This may cause it to show false positive pregnancy results.
  • Infertility treatment with hCG. Frequently common reason for a false positive pregnancy test is when women are using hCG injections in order to assist in getting pregnant – it means that hCG levels may register even when a pregnancy does not exist. If you have had an hCG shot due to infertility treatments, you need to be sure the shot is out of your system before you attempt to use early pregnancy tests.
    Normally a blood test or obstetric examination helps to determine a true pregnancy from a false one.
  • Additional medications. Some medications may cause a false positive on a pregnancy test. These include anti-convulsants, medications to treat Parkinson’s disease, certain tranquilizers, and certain diuretics. Many of these medications could be dangerous to a growing unborn child. Special consultation with your obstetrician is needed.
  • “Chemical Pregnancy”. The terminology “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.
  • 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 interpreted as a positive result.
  • Quality of your pregnancy test. As any product in the market, pregnancy tests also can have different kinds of quality, accuracy and expiration dates. Just be careful and check the quality of the product – read instructions, expiration date and accuracy indications.
  • Trophoblastic tumors. This kind of tumors can grow in women’s reproductive system and they can provoke false pregnancy positive test. The main reason for false pregnancy test is increased volume of HCG produced by trophoblastic tumors. These tumors can also provoke false pregnancy symptoms – morning sickness, swelling in the abdomen, strange feelings, etc.
    Early diagnostics of trophoblastic tumors is a guarantee for successful treatment. Check also Molar Pregnancy.

Can you be pregnant if the pregnancy test is negative?

The answer to this question is – YES. Sometimes you can be pregnant if the home pregnancy test results are negative. This may be due to a number of reasons and is called a false negative pregnancy test. It means that you are actually pregnant and the test results are misleading you and your doctor.

Main Causes for False Negative Pregnancy Test

  • Too early! One reason for a false negative pregnancy test could be that you took the test too early for the Human Chorionic Gonadotropin (hCG) to be present in your blood. Pregnancy tests vary in their sensitivity which means how soon they can detect the hormone hCG in your urine. It is possible that although your ovum might be fertilized, meaning you may be pregnant, but your body has not started secreting enough hCG for the test to measure. Your body needs at least 14 days after ovulation for the hormone to rise to a high enough level to be detected in a test.
  • Errors – unreliable technique! Improper testing can lead to false negative results. There is a possibility that while using the home pregnancy test strip you either did not dip it well or did not hold it well in your urine stream, depending on the test you are using. This error in technique may give false negative results.
  • Time/Duration! For accuracy in home pregnancy tests it is essential that you read the test results in the stipulated reaction time. All test kits indicate their specific reaction time on the package itself. Pregnancy test instructions will specify when test results should be interpreted and when test results are no longer valid. If you let the test stay too long (more than indications in the instruction), the test is invalid. This may cause it to show false negative results.
  • Defective pregnancy tests. Expired tests or faulty home pregnancy tests can also lead to false negative results. Always check the expiration date before testing to assure accurate results. Keep in mind, even with the highest quality control, an occasional defective test may occur.
  • If your home pregnancy test shows negative results but you still think you could be pregnant and/or feel pregnancy symptoms – wait few days and try again. A negative result can mean three things – 1) either you are not pregnant, or 2) you took the test too early or 3) you took the test wrongly. Also, if you have received different answers on multiple pregnancy tests, it is strongly recommended to get a blood pregnancy test done for more accurate answer.

What to do if you have doubts about pregnancy test results?

  1. During shopping try to choose two different brands – selecting and using two different brands of pregnancy tests will give you a better chance of avoiding the false positive or false negative results. If you get the same reading on both tests then the result is most probably = correct. If you have two different readings on two different tests then there is something wrong with one of selected tests.
  2. Discuss your problem with your gynecologist – no matter what the result is (positive false or negative false). Gynecologist can always confirm pregnancy or confirm absence of expected pregnancy. It is also very important – if there is a false positive result because of a medical condition then that is something that you and your doctor can discuss. Trophoblastic tumors should be excluded.
  3. Be sure that test was done in clean conditions – keep everything clean including test elements, urination and body area involved. If you are using a collection cup for your test make sure that there are no detergents left on the cup. This will help to give a more accurate reading.
  4. Follow all pregnancy test instructions – follow the directions on the package. Some tests are different and to get the best result it is important to follow the directions properly.
  5. Evaluate your health conditions and medicine used – clarify and try to understand – the medicines you are taking and whether or not you have any conditions or are on any medications that could possibly give you a false positive reading.

Although pregnancy tests are supposed to be 97%-99% accurate that still means that 1 out 100 women testing could have a problem. Make sure that you follow the directions on the test completely and always check your basal temperature and possible pregnancy symptoms.


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