Pregnancy is usually detected in the mother’s blood serum one day after the fertilized egg is deposited. A fertilized egg is formed when a woman’s egg cell and a man’s sperm combine. About 6 to 7 days after the fertilized egg is formed, the follicles form trophoblast cells and begin to secrete HCG. Generally, HCG begins to appear in the blood on the 1st day after fertilization and can be detected in the blood, reaches a peak at 8-10, and begins to decline thereafter. HCG appears in urine later than in blood, and it takes about 7-10 days for HCG secreted by trophoblast cells to enter urine, so pregnancy can be detected by blood on the 1st day after fertilization, and by urine on about 7-10 days. Blood HCG test is the most accurate, sensitive and fastest means of determining pregnancy, and pregnancy can be detected by testing peripheral blood HCG levels.