1. Division of Maternal-Fetal Medicine, Department of Obstetrics-Gynecology, West Los Angeles Kaiser Permanente Southern California Medical Group, Los Angeles, CA 90034, USA
2. Division of Maternal-Fetal Medicine, Department of Obstetrics-Gynecology, University of California, Irvine, CA 92868, USA
3. Department of Research & Evaluation, Kaiser Permanente Southern California, Pasadena, CA 91101, USA
4. Department of Obstetrics and Gynecology, University of Medicine and Dentistry New Jersey, New Brunswick, NJ 08901, USA