1. Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, California
2. Preterm Birth Initiative, University of California, San Francisco, San Francisco, California
3. Department of Biostatistics, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland
4. Division of Epidemiology, School of Public Health, University of California, Berkeley, Berkeley, California
5. Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California
6. Center on Social Disparities in Health, Department of Family and Community Medicine, University of California, San Francisco, San Francisco, California
7. Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California