When you’re trying for a baby, you want to know as quickly as possible if your efforts have paid off. If you suspect that you might be pregnant, you can’t wait for an appointment with your doctor or a lengthy blood test. Who wants that kind of stress? Luckily, there’s a more convenient option. Since the 1970s, home pregnancy tests have been available that can detect pregnancy fairly reliably. The creators of these devices try to make them easy to use, but you almost certainly have questions about how they work, when you should use them, and when they may give false results. Let’s explore these issues and hopefully understand these tests a little better.

How They Work

Home pregnancy tests measure the human chorionic gonadotropin (hCG) hormone in your urine. After implantation, the placenta releases hCG, which signals to the ovaries to release progesterone during early pregnancy.

Different pregnancy tests check for hCG in different ways. A qualitative test is binary, answering the question “are you pregnant?” by detecting the presence or absence of hCG. A quantitative test can measure different levels of hCG, even detecting the hormone at very low levels. These can be used to detect problems during pregnancy and may be used to rule out ectopic pregnancy.

Most doctors recommend waiting until you’ve missed your period to take a home pregnancy test. This is usually about two weeks after conception, and it takes seven to 12 days for hCG levels to rise enough to ensure a proper test. However, because it takes time, it’s possible to have a negative result, wait a week, and find out you’re pregnant after taking another test. It never hurts to be patient.

False Indicators

Home pregnancy tests are around 99% accurate. Unfortunately, it is possible for a pregnancy test to give a false positive. This can happen for several reasons:

  • So-called “chemical pregnancies” occur when a fertilized egg fails to implant during the earliest stage of pregnancy. The hCG hormone is still released for a short time, causing the test to read positive.
  • Ectopic pregnancies <<LINK TO ECTOPIC PREGNANCY BLOG>> can also produce hCG, even though the fertilized egg implants somewhere other than the uterus. Unfortunately, these pregnancies are not viable and may cause severe health problems.
  • Following recent pregnancy loss, enough hCG may still be present to trigger a false-positive.
  • The hCG hormone can also be produced by tumors, particularly germ cell tumors in the eggs.

User error and defects in the test device can also lead to false readings, both positive and negative. False negatives are more likely to occur because:

  • You took the test too soon.
  • The test has passed its expiration date.
  • You didn’t follow the exact directions and accidentally took the test wrong.
  • You drank too much liquid before taking the test and diluted your urine.
  • You are taking certain medications, including antihistamines.

If you think you might be pregnant and have questions about the accuracy of a home pregnancy test, talk to your doctor. Blood tests and doctor-administered urine tests are even more accurate than home tests for detecting pregnancy and can detect it sooner, but they are hardly as convenient. If you want more information about improving fertility or tips for trying to conceive, follow us on Facebook and Twitter, or sign up for our newsletter below.