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How Common Are False Positives? Pregnancy Test 101

by Joan Newsome

When having unprotected heterosexual intercourse, chances are high that the woman will get pregnant. Some ladies panic when they look at the positive results of a pregnancy test, which is natural if you’re someone who doesn’t want children yet.

Yet, there are certain times when a pregnancy test will show a false-positive result. But how common are false positives and what causes them in the first place?

A typical pregnancy test needs to do one thing — spot if there is any human chorionic gonadotropin or hCG in a woman’s urine. hCG is also called the pregnancy hormone; once the woman’s egg is fertilized, hCG production will increase rapidly in her body. So, if there’s hCG in the urine, the woman is pregnant, right?

Well, it’s not that simple. In order to answer the how common are false positives question, let’s look at the list of possible causes for false-positive results.

How Common Are False Positives: Seven Causes for Positive Results

Ectopic Pregnancy

Sometimes the fertilized egg will find its way out of the uterus. It can be in the cervix, the fallopian tubes, the ovaries, or the abdomen. This is called an ectopic pregnancy; the woman’s body will still produce hCG during this process, even if the egg can’t thrive in its current environment.

Ectopic pregnancies can have extremely negative effects on your health. Make sure to seek medical help (for yourself or your partner) if you spot any of these symptoms:

• Sharp pelvic or abdominal pain
• Spotting
• Bleeding
• Dizziness
• Fainting
• Pressure in your rectum

Chemical Pregnancy

When a fertilized egg is unable to grow or implant, the woman is going through something called a chemical pregnancy. Her egg will still produce more hCG and show a false-positive result on the test, but the egg won’t start to develop into a fetus.

These types of pregnancies are quite common and science is unable to figure out why they appear. Most women have this diagnosis because they take the test too early. If you wait for at least a week, chances are that the hCG will be gone from your system (or that of your loved one) and that the test will show a negative result.

Recent Abortion or Miscarriage

Both abortions and miscarriages show false-positive results for the same reason. Even after the woman has lost the fertilized egg, her body continues to produce hCG for the following six weeks or so. Naturally, the amount of this hormone will gradually fade, but if you try to conceive too early after either miscarriage or an abortion, chances are that you will get false-positive results on the test.


Interestingly, there are certain meds that trigger false-positive pregnancy results. The most common ones are synthetic hCG trigger shots, usually prescribed as fertility meds, which include:

• Profasi
• Ovidrel
• Pregnyl
• Novarel

As their descriptor suggests, these meds boost a woman’s hCG production. With that in mind, they will definitely produce more of the hormone, and it will show on the test.

However, there are other meds that can have a similar effect. They include certain antihistamines, diuretics, anticonvulsants, antipsychotics, meds that relieve anxiety or Parkinson’s disease, and methadone.

Various Medical Conditions

There are more than a few health conditions that can cause a hormone disbalance and trigger a positive result on a pregnancy test. By far, the most common health issues that do that are urinary tract infections, kidney diseases, and ovarian cysts. Ovarian cancer is also a frequent culprit behind false positives. And though it rarely happens, pituitary gland problems can also cause excess hCG to form.

Evaporation Line

Sometimes, the test itself can be the reason behind your conundrum. Usually, a pregnancy test will show two lines for pregnancy and a single line for the opposite. But when the urine evaporates from the test, there’s a high probability that a thin evaporation line will form. There are lots of women who mistake this line for that important pregnancy indicator, and I fully understand why it would.

There’s a simple solution to this issue. You simply need to buy a different test and try again. If possible, get one that uses messages like ‘pregnant’ and ‘not pregnant’ instead of the lines. Those tests have proven to be far less likely to cause confusion and false-positives.

User Error

When asking, How common are false positives? few people think that they might be the ones responsible for the incorrect result. Lots of users either take the test too early or don’t do it properly. So, ladies, here are a few tips on how to take the pregnancy test:

• Don’t take it too early during your cycle
• Take it in the morning, when your urine isn’t diluted with water
• Make absolutely sure that the test hasn’t expired
• Don’t keep the test in the urine for too long (or not long enough)
• Read the manual in detail, just in case you missed anything

How Common Are False Positives and What to Do When Spotting One?

Overall, false positives are not as common as true ones. But when you or your partner feel pregnant, always talk to a medical expert. Make sure to discuss every important detail (date of conception, how long it was until the missing period, etc.)

How Common Are False Positives: Final Thoughts

If there should be one takeaway from this text, it’s this: anything is possible when it comes to the human body. A woman might be pregnant and not know it, but she can also appear pregnant only to find out that it isn’t true. But no matter what happens, always remember to talk to a medical expert about pregnancies. That way, you can learn everything there needs to be known on the matter.

So, at the end of the day, how common are false positives? Well, common enough to warrant this text, but uncommon enough for most of the ladies not to feel concerned.