The births of more than 100 apparently normal infants at term following pregnancies initiated by in vitro fertilization and embryo transfer testifies to the successful clinical application of insights obtained from studies in reproductive biology over the last 20 years. In women, these studies have included: 1) characterization of the changes in blood hormone profiles throughout ovulatory menstrual cycles; 2) documentation of the hormonal composition of antral fluid in developing and degenerating preovulatory follicles; 3) correlation of these observations with the state of oocyte maturation...