Urine or blood tests used to detect whether a woman is pregnant.

The earliest way to know for sure whether you are pregnant is to have a pregnancy test. The fertilized egg at about 4 days old begins to secrete a hormone called human chorionic gonadotropin (HCG). Initially, it can be detected in the mother's blood, and shortly thereafter it is detected in the mother's urine.

Human chorionic gonadotropin is not found in the urine of non-pregnant women. Immunologic pregnancy tests employ antibodies...