A pregnancy test looks for a specific hormone in the urine or blood to detect pregnancy. Human chorionic gonadotropin is the name of the hormone (HCG). After a fertilized egg implants in the uterus, HCG is produced in a woman’s placenta. It’s usually only made during pregnancy. This test involves the Serum PT and the Urine PT. The Serum PT can find smaller amounts of HCG, and can confirm or rule out a pregnancy earlier than a Urine PT test. Serum PT tests are about 99 percent accurate.