How Do Home Pregnancy Tests Work?

Oct 02, 2009
Many women, who are trying to conceive, want to know if they are pregnant as early as possible. Using home pregnancy tests is the easiest and the most convenient way to know if you are pregnant at the comfort of your own home.

Home pregnancy test is a tool that is meant to determine if a woman is pregnant from home. The test measures the presence of human chorionic gonadotropin (hCG) hormone in the urine. This hormone is released by the placenta after the implantation of the fertilized egg takes place. This usually occurs from 6 to 12 days after conception.  After the egg implants to the uterine lining, the level of hCG hormone starts to increase.

Types of Home Pregnancy Tests

There are two basic types of home pregnancy tests: tests strips and midstream tests. With tests strips, you need to collect urine in  a container and hold the strip for 10 seconds to see the results. Midstream tests do not require you to collect the urine, but instead you need to hold the test in our urine stream.

You can also find early home pregnancy tests that claim to predict if you are pregnant as soon as 7 to 10 days after ovulation. These pregnancy tests detect the level of hCG hormone at a level 20 mIU, which is present at about 7 days after ovulation. Other pregnancy tests determine the level 50 to 100 mIU, which is present in the urine at about 12 days after ovulation.  

How early can you take pregnancy test?

Nowadays, most home pregnancy tests claim to give a reliable result on the day of the missed period. Early home pregnancy tests give a possibility to detect pregnancy as soon as 7 to 10 after ovulation. But most specialists agree that you need to wait one week for the most accurate results. This is because the level of hCG hormone in the urine is different during early pregnancy and may vary for different women. Taking the home pregnancy test too early may not give the accurate answer because the level of hCG hormone can be too low or the test may not be sensitive enough to detect pregnancy so early.

Are Home Pregnancy Tests Accurate?

Many women are concerned about home pregnancy tests accuracy. Most home pregnancy tests are claimed to be 99 percent accurate. But the accuracy rate may depend on different factors:

Sensitivity of the test

Early home pregnancy tests with 20 to 25 mIU/ml level can give the answer as soon as 7 to 10 days after conception. However, it is important to not that conception can occur several days after sexual intercourse and the results may be negative if you take early pregnancy test so early.

Home pregnancy tests with 50 to 100 mIU/ml give an accurate result around two weeks after conception.

Proper Use of the Test

It is important to carefully follow the instructions to have more accurate result when using home pregnancy tests. Always check the expiration date on the home pregnancy test before buying it. Also make sure you hold the tests strip in a container or in your urine stream according to the specified time to receive accurate results. Waiting too long or not long enough may affect the results. Some medications like certain fertility drugs may also affect the results of home pregnancy tests.

Time When the Test is Used

Taking home pregnancy test one week after the missed period will give more accurate results than the test used on the first day of your missed period. Also try to use your first morning urine to detect pregnancy with home pregnancy test, because in the morning the concentration of the hCG is the highest.

Reading the results of home pregnancy tests

Many women are confused about the results of home pregnancy test. Usually it takes 2 to 5 minutes for the answer to show. If you are pregnant, the two lines or plus sign or "pregnant" sign, depending on the brand of home pregnancy test, will appear on the test window.

If the second line on home pregnancy test is faint enough, this usually means that you are pregnant. However, it is recommended to take another test after several days. Take the first morning urine before drinking any fluids to get more accurate results.