After ovulation, the empty Graafian follicle contains a blood clot which is called corpus haemorrhagic. Its granulosa cells continue to proliferate, develop yellow carotene pigment or lutein and get converted into lutein cells. This converts the ruptured follicle into yellow body called corpus luteum. It becomes a temporary endocrine gland secreting progesterone with small quantity of estrogen. in absence of fertilization, after few days, corpus luteum ultimately stops activity, loses yellow colour, begins to degenerate, then it is called corpus albicans. If fertilization occurs and foetus is implanted in the endometrium, the trophoblast cells of the developing placenta secrete a hormone human chorionic gonadotrophin (hCG). This hormone, like LH, maintains the corpus luteum and the secretion of progesterone and estradiol by it. These two hormones check the breakdown of the endometrium of the uterus. Thus corpus luteum helps to maintain pregnancy.