What is a pregnancy test and how does it work?

Pregnancy tests are designed to tell if your urine or blood contains a hormone called human chorionic gonadotropin (hCG). This hormone is produced right after a fertilized egg attaches to the uterus. This usually happens but not always about six days after fertilization. If you're pregnant, levels of hCG continue to increase rapidly, doubling every two to three days.


What types of pregnancy tests are available?

Two main types of pregnancy tests can let you know if you're pregnant: urine tests and blood tests.

Urine tests can be done at home or in a doctor's office. Many women first choose a home pregnancy test (HPT), about a week after a missed period. Home pregnancy tests are private and convenient.

These products come with instructions. Follow them closely for the most accurate results. After testing, you can confirm results by seeing your doctor, who can perform even more sensitive pregnancy tests.

Blood tests are done at your doctor's office, but are used less often than urine tests. These tests can detect pregnancy earlier than a home pregnancy test, or about six to eight days after ovulation. But with these tests, it takes longer to get the results than with a home pregnancy test.

Two types of blood pregnancy tests are available:

A quantitative HCG test (beta hCG) measures the exact amount of hCG in your blood. It can find even very low levels of hCG. Because these pregnancy tests can measure the concentration of hCG, they may be helpful in tracking any problems during pregnancy. They may also be used to rule out a tubal (ectopic) pregnancy or to monitor a woman after a miscarriage when hCG levels fall rapidly.

A qualitative HCG test simply checks to see if hCG is present. It gives a "yes" or "no" answer to the question, "Are you pregnant?" Doctors often order these tests to confirm pregnancy as early as 10 days after a missed period. However, some of these tests can detect hCG much earlier.