Sperm banks around the world have made a disturbing finding: the quality of what donors provide is declining. In Israel, it's happening twice as fast as any place else. So far, it's a development nobody can explain. Danish scientists discovered it first, but it's happening elsewhere, including in the United States. It's a potential crisis of human fertility. Birth rates aren't going down yet but male sperm counts are. Dr. Sherman Silber is Director of the Infertility Center of St. Louis. Dr. Ronit Haimov-Kochman is a reproductive endocrinologist and infertility researcher at the Hadassah Hebrew University Medical Center in Jerusalem.