At-home pregnancy tests can vary in their sensitivity, but all of them work the same way.
With just a sample of urine, these tests can detect human chorionic gonadotropin (hCG). This hormone level is elevated during early pregnancy. If an at-home test is positive, you should see an obstetrician or a gynecologist who will use more sensitive tests (such as qualitative and quantitative blood tests) or an ultrasound to confirm the pregnancy and its stage of development.
Can you trust the results of a drug store pregnancy test? In general, these tests are considered trustworthy and accurate. But false-positive and false-negative results are possible.
9 reasons your pregnancy test results may be unreliable
1. Taking the test at the wrong time
Some at-home urine tests can detect the hCG hormone even before you miss a period. The results are more accurate if you take the test after you miss your period – even the very next day after you expected your period to begin. The determination is also more trustworthy if you test your urine first thing in the morning when it's most concentrated.
2. User error
To get an accurate result, follow the test kit manufacturer's instructions precisely.
- use an expired test kit
- remove the stick from the urine stream too early or too late
- test an inadequate amount of urine
- drink too much liquid before taking the test (diluting your urine)
- misread the results (like mistaking a faintly colored urine evaporation line for the test result)
- check the results too early or too late
3. Certain medications
Taking diet aids or fertility drugs could affect your pregnancy test results. If you're undergoing fertility treatment, see your doctor to confirm at-home pregnancy test results.
4. Chemical pregnancy
A chemical pregnancy is an unsuccessful early pregnancy in which the embryo can't implant and grow. When this happens, it's not due to anything the woman has done. It may be caused by genetic factors, a hormonal imbalance (low progesterone levels) or uterine fibroids, scar tissue, or an irregular-shaped uterus. Though a chemical pregnancy can trigger a positive pregnancy test result, the pregnancy cannot develop properly. This type might be widespread, though it goes undetected when the woman doesn't take the test early on.
5. Ectopic pregnancy
An ectopic pregnancy happens when an embryo implants outside of the uterus, such as in a fallopian tube, the cervix, an ovary, or the abdominal cavity. This type of pregnancy isn't viable because there's no place for the embryo to grow. Yet, it can still cause a positive pregnancy test result due to the presence of the hCG hormone.
Ectopic pregnancies are medical emergencies. They can be harmful if left untreated.
- sharp abdominal pain
- pain in the pelvis, shoulder, or neck
- vaginal spotting or bleeding
- dizziness or fainting
- rectum pressure
If you're experiencing any of these symptoms while pregnant, seek immediate medical attention.
6. Molar pregnancy
This is another type of nonviable pregnancy that can cause a positive pregnancy test result but won't develop into a fetus. This type of unsuccessful pregnancy is due to a genetic abnormality or the premature division of sperm. With a molar pregnancy, an embryo might not form or the placenta is abnormal. Women with this type of pregnancy might experience miscarriage or may need a medical procedure to remove the undeveloped cells.
7. Other medical conditions
While it is rare, certain medical conditions can potentially affect pregnancy test results. These include:
- urinary tract infection
- cancers of the ovary, bladder, kidney, liver, lung, colon, breast, and stomach
- kidney disease
- ovarian cysts
- pituitary issues in peri-menopausal and menopausal women
- tumors in the placenta cells
- "phantom hCG" (antibodies affect the test kit)
8. Recent birth, abortion, or miscarriage
If you have recently given birth or lost a pregnancy due to miscarriage or abortion, you may still test positive for pregnancy for up to six weeks. This false-positive pregnancy test result is due to the continued presence of elevated levels of the hCG hormone.
9. Menopause or post-menopause
While it may seem impossible, women who are going through menopause or have already gone through this hormonal change can have detectable levels of hCG in their urine and blood. Even though women at this stage can't get pregnant, they can get a false-positive pregnancy test result.
Medically reviewed by Karla Maguire, M.D., gynecologist and obstetrician with the University of Miami Health System. Written by Dana Kantrowitz, contributor to UMiami Health News.
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