This is an adult ovary with two corpora lutea. The larger one at the top is a hemorrhagic corpus luteum of menstruation, and the smaller one at the bottom is involuting from a previous menstrual period. If implantation of a fertilized ovum occurs, then the corpus luteum will persist because of HCG from the placenta. Of 400,000 ovarian follicles present at birth, only about 400 will mature to the point of ovulation during childbearing years.