Human chorionic gonadotropin (hCG) is a hormone measured by pregnancy tests and produced by the developing placenta immediately after successful fertilization. Under normal conditions and after ovulation has occurred, hCG can be detected in urine 9-10 days after the implantation of the fertilized egg in the uterus and doubles every 2-3 days, reaching 100mlU/ml by the first missed period. The appearance of hCG soon after conception and the subsequent increase in its concentration during the early days of pregnancy make it an excellent marker for the early detection of pregnancy.