1. Perinatal Epidemiology and Health Outcomes Research Unit, Division of Neonatology, Department of Pediatrics, Stanford University School of Medicine and Lucile Packard Children’s Hospital, Palo Alto, California;
2. California Perinatal Quality Care Collaborative, Palo Alto, California;
3. Department of Biostatistics & Bioinformatics, Duke University, Durham, North Carolina;
4. Department of Applied Mathematics and Statistics, Baskin School of Engineering, University of California, Santa Cruz, California;
5. eBay Research Laboratories, San Jose, California; and
6. Veteran’s Affairs Palo Alto Health Care System, Palo Alto, California