1. Department of Anesthesiology, Columbia University Vagelos College of Physicians and Surgeons, New York, New York
2. Department of Health Policy and Management, Columbia University Mailman School of Public Health, New York, New York
3. Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Columbia University Vagelos College of Physicians and Surgeons, New York, New York
4. Department of Epidemiology, Columbia University Mailman School of Public Health, New York, New York