3 Things You Need To Know About Pregnancy Test False Positives

False positive pregnancy tests are confusing, panic-inducing and sometimes devastating. Read on to learn what you need to know about false positive pregnancy tests.

Pregnancy Tests – Expectation vs. Reality?

False hopes are the worst. You might have expected something great to happen, found proof that it will finally happen but then have those soaring feelings of hope deflated upon finding out that – “Oops, sorry! It’s not actually happening! Try again next time.”

But, such is life and pregnancy tests are no exception. As pregnancy tests are only 99.9% accurate, it may still sometimes display incorrect results – a false positive, for example.

What exactly is a “false positive” on a pregnancy test?

A false positive means that the pregnancy test shows positive results confirming that you are pregnant. However, a few weeks later, you find out that you are not pregnant after all. Maybe you’ll get your period or maybe you’ll visit your doctor and they’ll confirm that the results were a false positive. 

False negatives may also occur. The opposite of a false positive – a false negative means the pregnancy test shows negative results but you are, in fact, pregnant.

These results happen because, as mentioned, since home pregnancy tests are never 100% accurate, there is still a chance that it can show incorrect results.

What do inaccurate pregnancy results mean for women?

Inaccuracy is always annoying. As much as possible, we always want to be prepared for whatever life has in store for us. And this is most especially true for women who are either trying to conceive or women who are avoiding getting pregnant – whether women want children or not, as much as possible, they do not want to be taken by surprise.

Inaccurate pregnancy results can mean a great deal of stress and disappointment. 

Here’s how false positives may affect women:

  • For women who are working hard to have children, a false positive can mean crushing hopes and anticipation of finally having a child.
  • For women who simply prefer not to have children or are not ready yet, a false positive can cause panic, stress and overthinking, only to find out that they weren’t pregnant at all.

The effect can range from mild annoyance to extreme dismay, depending on the circumstance. To illustrate, let’s do a little role play:

Imagine wanting a child so desperately, you’ve spent thousands and invested so much time, energy and emotions into conceiving but then weeks after the elation of getting your first positive result, you get your period. How would you feel? Devastated would probably be an understatement. Women are resilient, though. You would probably pick yourself up and try again – more carefully, this time.

On the other side of the spectrum, imagine being a woman who has worked hard to avoid having children. Let’s say you’re a woman who has the tremendous responsibility of caring for sick, elderly parents. Because of this, you have decided that having a child is not something you are ready to handle in your life right now. Your long-time boyfriend understands that and also shares your opinion. If you get a false positive, the stress that causes can be frustrating, to say the least. Even if later, you do get your period and you realize that “Oh, that was a false positive”, it’s still annoying and you’d make sure it doesn’t happen again.

This article will serve as a guide to knowing the reasons behind a false positive and understanding how pregnancy tests work. Our goal is to help all women ensure that they will get the most accurate results from a home pregnancy test.

We’ll talk about how pregnancy tests work and the top 5 reasons why a pregnancy test may show false positive results.

A Quick History Lesson on Pregnancy Tests

A Quick History Lesson On Pregnancy Tests

To understand false positives, though, it’s best to start at the very beginning – 1350 BCE, Ancient Egypt.

Women in Ancient Egyptian culture used wheat and barley seeds to find out if they were pregnant. It is one of the earliest known ways to test for pregnancy.

To understand false positives, though, it’s best to start at the very beginning – 1350 BCE, Ancient Egypt.

Women in Ancient Egyptian culture used wheat and barley to find out if they were pregnant. It is one of the earliest known ways to test for pregnancy.

How did the wheat and barley test work?

If a woman wanted to find out if they were with-child or not, then she would be asked to urinate on wheat and barley seeds. Over the course of several days, the woman waits to see if the seeds sprout. 

If the wheat seeds sprouted, the woman is believed to be pregnant with a girl. 

If the barley seeds sprouted, the woman is believed to be pregnant with a boy. 

If there were no sprouts, then she isn’t pregnant.

Since the Ancient Egyptians were considered one of the most advanced early civilizations in history, doctors in 1963 actually wanted to find out for themselves if there was some truth to their wheat and barley pregnancy test.

Surprisingly, the results were accurate. 

It only showed positive/negative results, of course, not the gender of the baby. The study showed that pregnant women’s urine did promote growth in the wheat and barley seeds while the urine of non-pregnant women did not promote any growth at all.

Here are other ways women tested for pregnancy before the invention of the home pregnancy test kit:

Onions and Bad Breath

Onions And Bad Breath

The Greek Father of Medicine, Hippocrates agreed on testing pregnancy with an onion and waiting to see what the woman’s breath smelled like in the morning.

Historical records show that women were asked to insert an onion into their vagina at night. If they woke up with onion breath in the morning, then she wasn’t pregnant. If she woke up with sweet-smelling breath (or the absence of onion scent), she was deemed pregnant.

Hippocrates believed that if the womb was open, the woman wasn’t pregnant and the scent of the onion would simply pass through. On the other hand, if the womb was closed, the woman was pregnant and the scent of the onion would not have any way to pass through.

It’s All In The Eyes

It's All In The Eyes

Fast forward to the 16th century, French surgeon Jacques Guillemeau who wrote a widely influential treatise on the subject of ophthalmology, believed that a woman’s pregnancy can be determined by carefully examining her eyes. 

According to Guillemeau, “a pregnant woman gets deep-set eyes with small pupils, drooping lids and swollen little veins in the corner of the eye.” 

While there is no medical proof whether eyesight determines pregnancy or not, Guillemeau was still right in the sense that a pregnant woman’s eyes are comparably different from before she was pregnant. In fact, today’s optometrists do not advise pregnant women to get prescription glasses and to wait until a few weeks after they give birth.

Of Rabbits and Mice… and Frogs.

Of Rabbits Mice And Frogs

In the 1920’s, pregnancy tests still weren’t an easy, one-step process as it is today.

Two German scientists, Selmar Aschheim and Bernhard Zondek, surmised that there was a specific hormone in pregnant women that were not present in non-pregnant women. Back then, they did not have the technology to identify that hormone but today, what the German scientists were referring to is known as the pregnancy hormone hCG or human chorionic gonadotropin.

How did Aschheim’s and Zondek’s pregnancy test work?

This test involved women’s urine and the lives of several hundred rabbits and mice.

According to the medical journals of their time, this type of pregnancy test involved collecting women’s urine which was then injected into rabbits and mice. After a period of 5 days, the animals were carefully opened up to check for results. 

If their reproductive parts showed significant changes, then the pregnancy results are positive. 

If there are no changes, then the pregnancy is negative. 

Women could request for faster results (well before the 5th day); however, it meant more rabbits and mice are to be killed.

These innocent animals didn’t fare well with this type of test but it seems to be the closest one that is similar to today’s blood & urine tests pregnancy tests.

In the 1940’s, another similar test was done on frogs, as well. Urine was injected into South African frogs; if the frog laid eggs, then the woman was considered pregnant.

The Invention Of The Home Pregnancy Test Kit

The Invention Of The Home Pregnancy Test Kit

In 1967, thousands of years after women tested pregnancy through urinating on wheat, barley, onions, rabbits, mice and frogs, American inventor and graphic designer Margaret Crane, invented the first home pregnancy test.

At that time, Margaret worked as a product designer for Organon International’s cosmetic line. She discovered that she could actually re-create an at-home version of a laboratory pregnancy test that she saw while on a tour of Organon’s facilities.

Margaret noticed individual test tubes filled with a specific mixture that, when combined with women’s urine, would determine whether the woman was pregnant or not. A red ring at the bottom meant positive results. She thought that the process of determining pregnancy was actually quite easy.

Believing she could make pregnancy testing a more private experience and one that could be done at home, she made a rough prototype made of objects she found in her own household. With a “paper clip holder, a test tube, a mirror, and a dropper”, she presented the prototype to Organon. They first rejected her invention but, seeing the invention’s potentials, they still applied for a patent for the invention in Margaret’s name.

Margaret’s first home pregnancy test invention was met with many setbacks, but in 1977, ten years after her invention, it was finally made available to the public.

Sadly, Margaret never made a single penny out of it due to patent and licensing complications. It was only in 2012 that she was finally recognized for her revolutionary invention.

Today, several brands and types of pregnancy tests are out in the market to choose from. From cheap dollar store brands or name brands producing digital pregnancy tests such as Clearblue; thanks to Margaret’s foresight and invention, determining pregnancy is no longer a complicated process as it was years ago.

How Do Pregnancy Tests Work?

The easy answer is:

Pee on the part of the stick with two lines and wait a few minutes. Two red lines mean positive; one red line means negative. In some pregnancy tests, it’s a plus sign or minus sign that determines positive or negative.

However, there is a bit more to it than that.

According to madehow.com, the tiny strip found on every pregnancy test is called the immunoassay strip. It is coated with a protein called Mab or monoclonal antibody that reacts once it detects the pregnancy hormone present in urine called hCG or human chorionic gonadotropin. If a woman is pregnant, she produces more hCG up until the end of her pregnancy.

Women are advised to take a pregnancy test early in the morning after sleeping for a good 8 hours as the hormone hCG is best detected during this time.

But, is the pregnancy test always accurate?

Even with its ease of use, however, there is always the question of accuracy. As mentioned at the beginning of this article, most pregnancy tests claim 99.9% accuracy but never 100%. Perhaps due to this, women up until today still question the home pregnancy test kit’s accuracy.

Due to questioning its accuracy, some women may:

  • wait longer than the recommended time to get a pregnancy test done to be perfectly sure of the results.
  • buy several different pregnancy test kits of different price range and brands.
  • Not trust pregnancy tests at all; maybe due to prior experience or stories from friends or family and prefer to head straight to the lab and get a blood test done, believing it is more accurate than a urine test.

And the belief of the pregnancy test’s inaccuracy is not completely unfounded. It is true that it can sometimes show results that are not entirely correct. One of the most common issues of pregnancy test results are false positives.

Why do false positives happen?

As defined at the start of this article, a false positive means exactly how it sounds like – the pregnancy test showing a positive result but upon further investigation, the woman finds out that she wasn’t pregnant after all.

Why does this happen? Is it because of a faulty pregnancy test? Was there something that should have been done differently?

To answer these common questions, read on.

The Top 3 Reasons Why False Positive Results Can Happen

The Top 3 Reasons Why False Positive Pregnancy Tests Can Happen

1. Pregnancy test kit instructions were not followed correctly.

Most women are sometimes in a rush to find out if they are having a baby or not and may sometimes not completely read the packaging instructions before going further with the test.

To get the most accurate results, it’s important to read all instructions closely and follow them to the letter. Here are couple of common scenarios that may happen if the packaging instructions are not followed:

  • The pregnancy test is read much later than instructed. Most pregnancy test kits would instruct to read the results within 5 minutes and no longer then 10 – 30 minutes after urine has been dropped or exposed to its strip. If left too long, the indicators on the strip may show two red lines which then looks like a positive result.
  • The pregnancy test is taken too early. Most pregnancy tests provide instruction for women to take the pregnancy test on the actual day of their expected period or a few days afterwards. Experts advise that “Implantation usually occurs about nine days after ovulation, and periods usually start about 14 days after ovulation.” Jumping to conclusions can’t be helped sometimes but it is still a good idea to wait and gather information: track when your last period was and when you are next to expect your period or use an ovulation app to help properly determine your ovulation period. You can also talk to your doctor or healthcare provider.
  • The pregnancy test is expired. Even pregnancy tests expire after a certain time. Taking the time to read the packaging ensures you can check the “best before” date. An expired pregnancy test does not give accurate results – it can either show a false positive or a false negative.

So, in order to get the most accurate results from a pregnancy test, aside from making sure instructions are read carefully, women must always ensure that there is ample time available when taking it and not take a pregnancy test in a rush to get to work or get the kids to school. If you rush, you won’t be able to read the package instructions carefully and, in your haste, cause incorrect results.

2. Pregnancy tests that follow a recent miscarriage or abortion.

Traces of hCG, the pregnancy hormone, can still be found in a woman’s body after miscarriage or an abortion. While the hCG levels fall after a pregnancy, it is usually still present within 9 to 35 days after a miscarriage or abortion but, according to the American Pregnancy Association, it can still be detected even after 4 to 6 weeks.

If you have recently had a miscarriage or abortion and suspect that you are pregnant, please consult with your doctor or healthcare provider to see when would be the most optimal and accurate time to check for possible pregnancy.

On the other hand, in cases of an extremely early miscarriage, the pregnancy test can sometimes read that as positive, too. According to pregnancy experts, most miscarriages actually happen within 13 weeks of pregnancy and it’s been found that many miscarriages actually happen before women find out they are pregnant.

Should an early miscarriage happen to you, this can result in a false positive result. The test reads positive, however, you will soon have your next period as you unknowingly miscarried. Doctors refer to this type of pregnancy as a chemical pregnancy.

Note: If your pregnancy test has a faint second line, this may be indicative of a chemical pregnancy.

3. Taking fertility medication and other types of medication that contain traces of hCG.

Women who are actively trying to get pregnant may be prescribed to take fertility drugs. Usually injected, fertility medication contains raised levels of hCG which can sometimes cause false positive results.

Most fertility specialists advise their patients not to take pregnancy tests so soon after taking fertility drugs so as not raise any false hope when a positive test result shows up.

Apart from fertility drugs, there are other types of medication that can cause false positives.

Per Healthline, here’s a quick list of common drugs that may interfere with pregnancy results:

    • antipsychotics, such as clozapine or chlorpromazine
    • anticonvulsants, like phenobarbital or other barbiturates
    • Parkinson’s disease medications, including bromocriptine (Parlodel)
    • diuretics, like furosemide (Lasix, Diuscreen)
    • antihistamines, including promethazine
    • methadone (Dolophine)

Apart from medication, certain medical conditions may also display false positive results, although these cases are very rare, if you are diagnosed with urinary tract infections, kidney disease or ovarian cysts, consult with your doctor or healthcare provider before taking a pregnancy test as this may sometimes show false positive results.


Millions of women rely on pregnancy tests and get accurate results. This means that, most likely, if a pregnancy test tells you that are pregnant then it is 99.9% correct. To ensure that it’s not giving you a false positive, however, follow packaging instructions carefully or consult with your physician first to make sure that your overall health, medication or ovulation period will not interfere with pregnancy test results.

Did you ever have a false positive or false negative result? If you did, we’d love to know your story. Share it below – we’d love to hear from you!


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