OH-Blog Logo
Jul 05, 2017 OHIOHEALTH
What is a False-Positive Pregnancy Test?

Is the stick always right? Usually yes, but sometimes no. Learn about the rare reasons for a false-positive pregnancy test.

A home pregnancy test has confirmed what you suspected — you’re pregnant. Home pregnancy tests work by detecting the presence of the pregnancy hormone hCG in your urine. Their results are considered reliable, especially when you wait for at least a week after you miss your period to use one.

They’re not foolproof, however. It is possible to get a positive result when you’re not actually pregnant, which is called a false-positive. If you’ve been looking forward to a positive pregnancy test result, a false-positive is disappointing. The good news is they’re rare. The best thing to do when you’ve gotten a positive result is to contact your doctor. A blood test will confirm that you’re pregnant.

What Can Cause a False-Positive Pregnancy Test?

Chemical pregnancy

A chemical pregnancy is a pregnancy, but an unhealthy one that results in an early miscarriage. A chemical pregnancy occurs when an egg has fertilized but doesn’t attach to the uterus. Usually, you will have a heavy period soon after your period is normally due. It’s estimated that 25-40 percent of pregnancies end as undetected miscarriages.

Recent miscarriage or birth

If you’ve had a baby recently or a miscarriage, you may test positive for pregnancy. When you’re pregnant, hCG levels rise quickly and peak at about 10 weeks. When a pregnancy ends, the levels go down, but slowly. The hormone can remain in your blood and urine for up to six weeks after a pregnancy ends.

Medications

If you’re undergoing fertility treatments to become pregnant, you may be getting hCG injections to stimulate ovulation. The medication can cause a false-positive result if you take the test too soon after a missed period. Other medications that can cause a false positive include:

  • Antihistamines
  • Antianxiety medications
  • Antipsychotics
  • Diuretics
  • Parkinson’s disease medications
  • Methadone

Defective test or user error

Before buying a home pregnancy test, check to make sure it hasn’t expired. If it has, the chemical used to detect hCG may not work. It’s important to read and follow the test instructions carefully. For instance, some tests require leaving the dipstick in the urine stream for a specific amount of time. Taking the test too early can also result in a false-positive.

How to Avoid a False-Positive Pregnancy Test

The best way to avoid a false-positive pregnancy test is to wait at least a week after you’ve missed your period to take the test. The level of hCG hormone will be higher and easier to detect. Detecting a chemical pregnancy before it miscarries can be emotionally hard.

Many home pregnancy test kits include two tests. If you get a positive result, you can wait a couple of days and use the second test. Then contact your doctor for a blood test to confirm the good news!

Looking for an OB/GYN? We can help!

TOP