It may be that you have taken a pregnancy test because you are actively trying to get pregnant. Or, perhaps quite the opposite, and you are concerned you are pregnant but not trying to conceive. Whatever the reason, false-negative or false-positive results can happen. Let’s look at pregnancy tests in a little more detail and why a false result may occur.
How do Pregnancy Tests Work?
Your body produces a hormone called Human chorionic gonadotropin (hCG) when you get pregnant. When a fertilized egg attaches to the lining of your uterus (right at the beginning of pregnancy), your body begins to release HCG. It starts to produce hCG around six days after fertilization.
Pregnancy tests detect hCG levels in the urine. hCG levels rise quickly, doubling every two to three days. Most pregnancy tests advise that they are accurate when taken from the first day of a missed period. But, if you don’t know when your next period is due or you have irregular periods, you can do the test at least 21 days after you last had unprotected sex.
Some pregnancy tests are more sensitive and claim you can use them before a missed period. However, they are not likely to be as accurate when taken early.
How accurate are home pregnancy tests?
Home pregnancy tests are usually very accurate. When taken on the first day of a missed period, some home pregnancy tests claim to be 99% accurate. This accuracy reduces the earlier you take the test before your missed period.
Home pregnancy test accuracy can depend on:
- When you take the test
- The time of day you take the test
- How you take the test
- The brand of the test
If you think you have a false test result, the best option is to wait a few days and then try again.
What are false pregnancy tests, and how do they happen?
Even though home pregnancy tests are very accurate, they can provide false results very occasionally.
- A false positive is a test result that shows you are pregnant when you are not.
- A false negative is a test result that shows you are not pregnant when you are.
Reasons your test might be wrong
False-positive results can occur due to:
- Reading the test after the recommended time frame. Some tests develop evaporation lines after a certain amount of time, making the pregnancy test look positive. Therefore, it’s important to read the test within the described time frame.
- A molar pregnancy (which is a condition where a tumor grows in the uterus mimicking pregnancy).
- Medications that contain synthetic hCG, such as some fertility medications.
- Medical conditions such as ovarian cysts, some cancers, kidney disease, or disorders that affect the pituitary gland and hormones.
- A recent miscarriage, incomplete miscarriage, or abortion where your hCG levels have not yet returned to normal.
False-negative results can occur if:
- You take a pregnancy test too early, before your missed period, so there is not enough hCG in your urine to detect.
- You check test results too soon, and it hasn’t had time to process correctly. It’s essential to follow the instructions on the pregnancy test packet or leaflet to have the best chance of getting an accurate result.
- You take the test late in the day, and your urine is more diluted. Although pregnancy tests can work at any time of day, you are more likely to get a more accurate result if you take a pregnancy test first thing in the morning. This is because hCG levels are more concentrated in the urine at this time.
Colorado Obstetrics & Women’s Health
If you are concerned that your pregnancy test result is false, you can see an obstetrician for a blood test. At Colorado Obstetrics & Women’s Health, our team of expert clinicians is here to support you through every stage of pregnancy. Right from before conception. Contact us today at (719) 634-8800 to schedule your appointment.