A pregnancy test is a medical tool used to determine if a person is pregnant. It works by detecting the presence of the hormone human chorionic gonadotropin (hCG) in urine or blood. This hormone is produced shortly after a fertilized egg attaches to the uterus. There are two main types of pregnancy tests: urine tests and blood tests. Urine tests can be done at home and provide quick results, while blood tests are usually performed in a medical setting and can detect pregnancy earlier. Both methods are reliable when used correctly.