HCG, also known as human chorionic gonadotropin, is associated with pregnancy and pregnancy-related disorders. Under normal circumstances, HCG can be measured in the blood seven days after fertilization because when you have intercourse after ovulation, the sperm and egg meet in the abdomen of the fallopian tube and unite, called fertilization. After fertilization, the fertilized egg divides and slowly moves towards the uterine cavity by the peristaltic movement of the fallopian tube, which is about 8-12 cm long, and it takes six days for the fertilized egg to reach the uterine cavity and be planted in the endometrium, at which time HCG can be measured in the blood, and 10-14 days later in the urine. HCG can be detected in special cases, such as within three weeks after miscarriage, within two weeks after delivery and in trophoblastic disease.