How Does a Pregnancy Test Work?

You’ve seen pregnancy tests in the pharmacy or in advertisements. You may ave even taken one before. But do you know how pregnancy tests work to tell you if you are expecting?

Pregnancy Test Strips Work By Detecting Hormones in Your Urine

From the earliest moments of conception, your body starts to undergo monumental changes. One of the very first signs of being pregnant is your body’s production of the pregnancy hormone, hCG (human Chorionic Gonadotropin), which can be detected in your blood and in your urine.

The amount of hCG in your body increases rapidly. It doubles every 36 to 48 hours as your pregnancy progresses, reaching its peak at eight to ten weeks. Pregnancy tests work by detecting the hCG hormone in your urine. When your urine comes in contact with the specially treated strip on a pregnancy test stick, results appear within minutes, indicating whether or not hCG, the pregnancy hormone, has been detected.

What happens when the pregnancy test detects the hCG hormone differs slightly by the brand and type of test. The basic way pregnancy test kits work is the presence of the hCG hormone creates a reaction within the test strip, which is then displayed as positive or negative results. Most tests have a results window and after a few minutes of contact with your urine will show two lines or a plus sign if you are pregnant, and a single line or minus sign if you are not.

How Early Do Pregnancy Tests Work?

Some at-home pregnancy kits are unable to detect hCG in urine until at least the first day of a missed period. If you want a pregnancy test that will give you early results, FIRST RESPONSE™ is the ONLY brand that tells you 6 days before your missed period.1 Try the FIRST RESPONSE™ Early Result Pregnancy Test, our #1 best-selling pregnancy test. And, for easy-to-read, unmistakable “YES+ / NO-” results in words, also try the FIRST RESPONSE Gold™ Digital Pregnancy Test.

Pregnancy is truly a life-changing event. Knowing if you are pregnant earlier allows you to make important decisions, such as adopting healthier lifestyle choices. You can begin taking better care of yourself and your baby sooner, in the first critical stages of your baby's development.

So, now you know how pregnancy tests work. Women have been getting pregnant for thousands of years, but home pregnancy test kits have only been available in the United States since 1977. A simple chemical reaction to detect the presence of hCG has been helping women and their partners get the news of pregnancy early and accurately for two generations.

1In one study, in 68% of the samples tested, pregnancy could be detected up to 6 days before the day of the missed period.