How Does A Pregnancy Test Work?

Pregnancy tests are easily obtained nowadays, and can give you results within minutes. But how does a pregnancy test work? And why are they not 100% accurate?

Two Types of Pregnancy Tests

There are actually two types of pregnancy tests: urine (pee) tests and blood tests. Urine tests determine the presence of the human chorionic gonadotropin (hCG) hormone in the urine. If it is present, there is a pregnancy. If not, then that means there is no pregnancy. These types of tests are readily available over the counter and also through a healthcare provider. They are also part of our no-cost services!

Blood tests not only determine if this hormone is present, but can also tell how much of it is present. These tests are useful when more diagnostic work is needed to help determine the health of a pregnancy. They are generally only available through a healthcare provider.

Why Test for hCG?

The reason that both of these pregnancy tests test for hCG is because the body only creates this hormone during a pregnancy. This hormone is actually produced by the placenta, an organ that the female body only grows during pregnancy, and then expels at the time of birth. After a fertilized egg attaches to the uterine lining, the placenta begins to grow, and the amount of hCG starts rising dramatically.* This usually occurs about six to ten days after conception. While detecting hCG this early in the pregnancy is possible, waiting until a missed period can offer more accurate results.

Pregnancy Test Accuracy

So why are these tests only 98-99% accurate even when used correctly?

False negatives most often occur if you take the test too early. There may not be enough hormone present yet to display a positive result. To minimize your chances of having a false negative, take the test after you’ve noticed a missed period. Taking the test in the morning may also give better results, because the hormone accumulates in the body overnight.

False positives happen less frequently than false negatives. The most common reason for a false positive is an extremely early miscarriage, either before or just after the fertilized egg attaches to the uterine wall, around the fourth week of pregnancy.*

A Negative Result

If you receive a negative result but still suspect that you are pregnant, it may be a good idea to retake the test in about a week. In the event that you start to experience abnormal symptoms, speak with your medical provider immediately. And if your period returns normally, you are most likely not pregnant.

A negative pregnancy test result can bring a great feeling of relief. But it can also serve as a reminder to make healthy sexual choices in your life. Check out this blog if you want to think more about your decisions about intimacy.

*https://my.clevelandclinic.org/health/diagnostics/9703-pregnancy-tests