1. Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, California
2. Division of Neonatology, Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, California
3. Division of Biostatistics, Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California