1. California Preterm Birth Initiative, University of California San Francisco, San Francisco, CA, USA
2. Department of Obstetrics, Gynecology & Reproductive Sciences, School of Medicine, University of California San Francisco, San Francisco, CA, USA
3. School of Social Work, University of Pittsburgh, Pittsburgh, PA, USA
4. Department of Epidemiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
5. Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA
6. Department of Behavioral and Community Health Sciences, School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
7. Division of General Internal Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, PA, USA