1. Program in Public Health, Department of Family, Population and Prevention Medicine, Stony Brook University, Stony Brook, New York
2. currently affiliated with Department of Population, Family and Reproductive Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
3. School of Public Health, University of California, Berkeley
4. Preterm Birth Initiative, University of California, San Francisco
5. Department of Epidemiology and Biostatistics, University of California, San Francisco