One of the consequences of cancer therapies, including radiation and chemotherapy, is gonadotoxicity. Alterations of the rate of follicle loss have been investigated in patients undergoing radiation and chemotherapy. The ability to predict the consequences of decay in the germ cell population depends upon determining a woman's current ovarian reserve, and there is presently no reliable method to accomplish this task. Female fertility is dependant upon a series of critical ovarian developmental events that are controlled by a large number of genes on autosomes and the X chromosome. Autosomal genes also play important roles in controlling follicular dynamics. The complexities of the events of fertility go beyond ovarian function. Two recent genome-wide association studies have identified loci associated with influencing age at menopause. Menopause on average occurs around age 52 years; however, natural fecundity ends upon average around age 41 years.