Understanding Pregnancy Tests: Urine & Blood
There are two types of pregnancy tests; one uses a urine sample, the other a sample of blood. Both tests detect the presence of a hormone called human chorionic gonadotropin (hCG). This hormone is produced by the placenta shortly after the embryo attaches to the uterine lining and builds up rapidly in your body in the first few days of pregnancy.
It is this rapid shift in hormones that triggers most of your pregnancy symptoms.