False Positive Pregnancy Test

False Positive Pregnancy Test


What happens when a woman has her periods missed? She normally goes to the pharmacy and gets a pregnancy test in the hope of, or scared, to see the positive result.

A Woman: False-positive Pregnancy Test

Express tests are believed to be approximately 100% accurate given all instructions are followed. However, the word “approximately” assumes some discrepancy. And as such, the test result might be false-positive.

Principle of Pregnancy Tests

Prior to discuss the reasons of such false results, one should understand the principle of this test. There are several types of pregnancy tests marketed though one underlying principle is common for all of them: some reagent reacts with the specific hormone produced by the chorion, that is, the expected placenta. Such reaction results in the color change or appearance of signs, depending on the type of tests.

HCG, Human Chorionic Gonadotropin, is produced the day after the fertilized ovum travels to attach to one of the uterus walls. This is the period when the chorion forms. Several days later the content of HCG reaches the value to be detected by the pregnancy tests as the sign of pregnancy.

Given that an ovum requires about 7 to 9 days for migration and several more days for hormone accumulation, the test result might be accurate after the first day of late periods.

It is supposedly easy to understand that no chorion means no hormone produced by it. So, how come women sometimes have their false-positive pregnancy results?

Why False Result

False Positive Pregnancy Test 1

The reasons for the above may vary depending on various factors, practical to tragic ones. But first things first. What to start with? The reasons, surely.

Defective or Expired Tests

Make sure you get the pregnancy test in a pharmacy with the due expiry date. This is what you start caring about. The expiry date is important for good reason and the outdated product is outdated and that’s it. It should not be used. The pregnancy test does not refer to expired food staff or medication to result in poisoning or side effects, though the final result will not be authentic, indeed. Use of expired tests is like a fortune-telling that might be true or not.

Defective tests are more difficult to identify, especially those for home use. And thus, a woman may rely on several test results only made with the interval of 1 to 2 days and the next time she is advised using tests from other packaging or of other manufacturer to be strict. Two tests bought in the same pharmacy are more likely to be from one and the same batch. And they both may be defective.

Non-compliance With Instructions

Non-compliance with the manufacturer’s instructions is the other reason of having a wrong result. So, if you bought the common testing strip, you should not put it under the stream of urine and likewise, the midstream stick is not immersed in urine. The same goes for the time of testing to hold the strip in the urine and the read results.

Abortion, Miscarriage or Embryectomy

When do the strips give false? For example, it is exactly false-positive after the abortion and miscarriage and the embryectomy, or removal of the fetus in tubular pregnancy. This is easily explained: when the pregnancy is terminated, HCG cannot be immediately excreted from the body and so far as it is in the blood, the result is false-positive.

In most cases, a woman is not affected with the false result if and when she is aware of the abortion or miscarriage event. However, a woman might not know about her pregnancy when the miscarriage occurs in the early stages long before she suspects the pregnancy. And the test done gives the result to be wrongly positive.

Cyst and Other Neoplastic Processes

Some women wonder, whether the test can be false-positive just before the periods? It may sound strange, but yes. For example, it occurs when a woman suffers from the stomach or ovary cysts. Other tumor processes might have the same effect, including malignant tumors.

So, if a woman expects her periods in the coming days but the test is positive, she’d better repeat it or see the gynecologist and have her blood and urine checked to make sure there are no tumors.

Administration of Medicine Containing HCG

If a woman is prescribed medications containing HCG like Pregnyl (the drug that stimulates ovulation), it makes no sense to check for pregnancy upon administration of this drug since HCG is excreted in 14 days, at least.

Hormonal Failure

False-positive test result may be caused by the hormone failure in females. In some other cases, the body starts producing other hormones that resemble HCG in structure and composition. High content of such hormones may also affect the test results.


And the final to mention is menopause. This is the period when the female body produces HCG in insignificant volume. This is too little to react with the test reagents. However, the result of the test may be wrongly positive when the hormone surge is revealed with the extremely sensitive pregnancy test.

In any case when the test results show you are pregnant but there is no factual pregnancy, you are advised to have a full medical examination to precisely identify the reason of the above and, if applicable, get the treatment.

One Comment

  • Mary says:

    Please, help me. I made a Clearblue test, it immediately showed bright plus, but the control window was empty. What happened?

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