Affiliation: | 1. Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California;2. Keck School of Medicine, University of Southern California, Los Angeles, California;3. Department of Obstetrics and Gynecology, Hospital Israelita Albert Einstein, Sao Paolo, Brazil;4. Childbirth Research Associates, North Hollywood, California |