1. Betty Irene Moore School of Nursing, University of California, Sacramento, CA, USA
2. Department of Obstetrics, Gynecology, and Reproductive Sciences, Preterm Birth Initiative, University of California, San Francisco, CA, USA
3. Department of Epidemiology and Biostatistics, and Office of Research School of Nursing, University of California, San Francisco, CA, USA
4. Department of Community Health Systems, University of California, San Francisco, CA, USA