1 Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, Box 0132, 490 Illinois St, 10th Floor, San Francisco, CA 94143. Electronic address: [email protected].
2 The Biostatistics Center, George Washington University, Washington DC.
3 Department of Obstetrics and Gynecology and Women's Health, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY.