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Human chorionic gonadotropin (hCG) is a glycoprotein hormone produced during pregnancy. It is made by the the developing embryo some time after conception and is produced again later by the syncytiotrophoblast (which is part of the placenta). Its role is to prevent the disintegration of the corpus luteum of the ovary and thereby maintain progesterone production that is critical for a healthy and normal pregnancy in humans. It is surmised that hCG might have additional functions, including an effect on the immune tolerance of the pregnancy. Because of the existence of hCG in the blood stream, it is an effective indicator/test for pregnancy.

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