Early Pregnancy test
All test depend on the detection of hCG. This test become positive at about 6 weeks after the beginning of the last menstrual period in urine and 8-12 days after the first missing of vaginal bleeding in blood.
The placenta and its secretion
The placenta forms upon completion of implantation. By the tenth week, the placenta is fully formed and has begun the production of specialized hormones such as hCG, progesterone and estrogen—both of which together prevent menstruation and the development of further egg cells within the mother. Remember, the placenta is the interface between the mother and the baby. Nutrients and waste products must pass across this membrane in order to support the developing embryo.