<P> If the egg is fertilized and implantation occurs, the syncytiotrophoblast (derived from trophoblast) cells of the blastocyst secrete the hormone human chorionic gonadotropin (hCG, or a similar hormone in other species) by day 9 post-fertilization . </P> <P> Human chorionic gonadotropin signals the corpus luteum to continue progesterone secretion, thereby maintaining the thick lining (endometrium) of the uterus and providing an area rich in blood vessels in which the zygote (s) can develop . From this point on, the corpus luteum is called the corpus luteum graviditatis . </P> <P> The introduction of prostaglandins at this point causes the degeneration of the corpus luteum and the abortion of the fetus . However, in placental animals such as humans, the placenta eventually takes over progesterone production and the corpus luteum degrades into a corpus albicans without embryo / fetus loss . </P> <P> Luteal support refers to the administration of medication (generally progestins) for the purpose of increasing the success of implantation and early embryogenesis, thereby complementing the function of the corpus luteum . </P>

What happens to corpus luteum after placenta takes over
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