Understanding Pregnancy Testing

Le résumé fourni par la source

Pregnancy tests are based on the detection of the hormone human chorionic gonadotropin (hCG) in human blood or urine; hCG is important for the development of the placenta and the fetus. The placenta is a disc of connective tissues around the embryo composed of different cell types in which villous syncytiotrophoblasts and trophoblasts specifically produce hCG from the period of implantation until the end of pregnancy. The synthesis of hCG starts 6–12 days after conception; this is the time when the growing embryo attaches to the uterus. The primary role of hCG is to maintain the corpus luteum (the luteinizing ovulatory follicle), which synthesizes progesterone and estrogen facilitating the development of cytotrophoblast cells. In the absence of hCG, the corpus luteum regresses to form corpus albicans. Progesterone prepares the lining of the uterus and relaxes the muscular wall to aid in the implantation of the embryo, while estrogen promotes organ growth and thickens the uterine lining.

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