1. Departments of Obstetrics and Gynecology (F.Z.S., S.W., D.R.M.) Los Angeles, California, 90033
2. Preventive Medicine (F.Z.S.), University of Southern California Keck School of Medicine, Los Angeles, California, 90033;
3. Department of Molecular and Cell Biology (J.H.), University of Cape Town, Private Bag, Rondebosch 7700, South Africa