False-Positive Pregnancy Test: 7 Possible Causes (2024)

User error is among the most common reasons for a false positive pregnancy test. This includes testing too soon after a recent abortion, miscarriage, or childbirth, misreading the lines on the test, or checking the test results outside of the recommended time frame.

Most at-home pregnancy tests use dipsticks placed in urine. The stick detects human chorionic gonadotropin (hCG), a hormone produced during pregnancy.

Home pregnancy tests can be highly accurate, but they aren’t foolproof. If you receive a positive result — even if you suspect it’s false — it’s important to make an appointment with a healthcare professional.

They can confirm the result and discuss your options moving forward, including pregnancy prevention, preparing for future pregnancy, or navigating an unexpected pregnancy.

Many home pregnancy tests boast a 99% accuracy rating. This figure is usually displayed in a large, eye-catching font on the front of the package.

The caveat — that the rating is based on tests performed by lab technicians — is typically explained in the fine print that folks may not notice or read.

This means many users expect a “perfect use” level of accuracy in a “typical use” environment prone to human error.

Some of the most common mistakes include:

  • using an expired test
  • taking the test too soon after sex
  • taking the test too soon after a recent abortion, miscarriage, or childbirth
  • drinking water or other fluids before taking the test
  • removing the dipstick from the urine outside of the recommended time frame
  • checking the test results outside of the recommended time frame

Some at-home tests show two lines when they detect hCG and one line when they don’t. The lines are usually pink, red, or blue.

If you check the test after the recommended time frame, you might notice a faint “evaporation line.” This can be mistaken for a positive test result.

The body produces the hormone hCG throughout pregnancy, peaking toward the end of the first trimester and gradually declining until pregnancy ends. Afterward, the hormone can remain in your blood and urine for up to 60 days.

The exact length varies from person to person and depends on whether the pregnancy was carried to term. The higher your hCG levels are, the more time it will take to return to your prepregnancy baseline.

If you’re actively trying to become pregnant, consider making an appointment with a healthcare professional. They can answer any questions and advise you on the best time to take a pregnancy test.

If you don’t have reason to suspect that a new pregnancy has occurred, retained products of conception (RPOC) may be present. Treatment may be necessary to remove lingering tissue or blood clots.

Symptoms of RPOC include:

  • heavy, irregular, or persistent vagin*l bleeding
  • unusual vagin*l discharge
  • lower abdominal or pelvic pain
  • fever

If you’re trying to end or prevent pregnancy, you might find it helpful to test again in 1 or 2 weeks.

If you continue to receive a positive result, it’s important to consult a healthcare professional. They can determine if termination was successful and advise you on any next steps.

“Chemical pregnancy” isn’t a medical term or recognized as a medical diagnosis. This means there isn’t an established, clinically agreed-upon definition or description.

Older research notes that a chemical pregnancy isn’t the same as a clinical pregnancy, which occurs when a fertilized egg implants in the uterine wall and begins to develop into an embryo.

Healthcare professionals can diagnose a clinical pregnancy with an ultrasound scan to look for the gestational sac.

A chemical pregnancy occurs when elevated hCG levels are the only indication of implantation.

The fertilized egg may develop into a blastocyst about 6 days after implantation. However, it doesn’t develop into an embryo, which occurs about 12 days after implantation.

Because of this, a chemical pregnancy may be colloquially referred to as an early miscarriage. These are often the result of chromosomal abnormalities. Treatment usually isn’t necessary.

Medical professionals consider chemical pregnancies to be common. Older data cited in a 2017 study suggests that this accounts for about 8% to 33% of miscarriages.

Ectopic pregnancy occurs when a fertilized egg implants and grows outside of the main cavity of the uterus.

Although ectopic pregnancies usually develop in a fallopian tube — which carries eggs from the ovary to the uterus — they can also occur in the cervix, ovary, or abdominal cavity.

An ectopic pregnancy is a medical emergency requiring treatment. The pregnancy isn’t viable because there’s no place for it to grow or develop outside of the uterus.

Symptoms of ectopic pregnancy include:

  • unusual vagin*l bleeding
  • low back pain
  • mild abdominal or pelvic pain
  • mild cramping on one side of the pelvis
  • pressure on your rectum

Symptoms of a ruptured fallopian tube include:

  • sharp, sudden abdominal or pelvic pain
  • shoulder pain
  • weakness, dizziness, or fainting

Ectopic pregnancy is considered rare, with national estimates ranging from 1% to 2% of all pregnancies in the United States. According to Planned Parenthood, about 2 out of every 100 pregnancies are ectopic.

Molar pregnancy occurs when human gametes (the egg and sperm) do not join correctly during fertilization.

Gametes are usually haploid, meaning they contain a single set of chromosomes. Chromosomes from the egg typically combine with chromosomes from the sperm to create a zygote. The zygote is usually a diploid cell containing two complete sets of different chromosomes.

A complete molar pregnancy occurs when sperm fertilizes an egg with incomplete or malfunctioning chromosomes. This causes fluid-filled cysts inside the uterus, and an embryo doesn’t begin to form.

A partial molar pregnancy occurs when two sperm fertilize an egg, resulting in a zygote with three complete sets of chromosomes. This causes abnormal tissue to form inside the uterus. Although an embryo may begin to form, it usually doesn’t grow or develop.

In either case, treatment is necessary to remove molar tissue from the uterus.

Symptoms of molar pregnancy include:

  • bright red to dark brown vagin*l bleeding
  • severe nausea and vomiting
  • grape-like clots of tissue expelled from the vagin*
  • pelvic pain or pressure

Molar pregnancy is considered rare. Older data cited in a 2021 review suggest that one out of every 1,000 to 1,200 pregnancies in the United States is molar.

Some fertility medications use hCG to help stimulate ovulation, including:

  • Novarel
  • Ovidrel
  • Pregnyl
  • Profasi

If you’re taking these or other medications with hCG, ask your prescribing physician about its effects on home pregnancy tests. They can help you determine when to test for the most accurate results.

Some people use over-the-counter hCG products for weight loss. It’s important to understand that the Food and Drug Administration (FDA) hasn’t regulated or approved these products, and weight loss claims are unsubstantiated.

In some cases, a condition unrelated to pregnancy can cause elevated hCG levels or “phantom hCG.”

This less commonly includes:

  • ovarian cyst
  • tubo-ovarian abscess
  • adenomyosis

People who are perimenopausal, menopausal, or postmenopausal may also experience elevated hCG levels.

In rare cases, abnormal hCG levels may be caused by:

  • choriocarcinoma
  • persistent trophoblastic disease (PTD), which is also known as an invasive mole
  • placenta site trophoblastic tumor (PSTT)
  • quiescent gestational trophoblastic disease (GTD)
  • paraneoplastic syndromes, which occur alongside certain cancerous neoplasms (tumors)
  • non-trophoblast tumor
  • familial hCG syndrome

Certain conditions, like urinary tract infections (UTIs), can interfere with urine test results. This is usually due to increased leukocytes (white blood cells), protein, or blood in urine.

Unexpected or inaccurate pregnancy test results happen.

If you received a positive test result that you think could be false, it’s important to make an appointment with a healthcare professional for further testing. They can also discuss your options for any next steps.

If you received a positive test result that you were upset to learn was false, know that you aren’t alone and support is available. A healthcare professional can answer your questions and help connect you to resources in your area.

Tess Catlett is a sex and relationships editor at Healthline, covering all things sticky, scary, and sweet. Find her unpacking her inherited trauma and crying over Harry Styles on Twitter.

False-Positive Pregnancy Test: 7 Possible Causes (2024)

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