1 Department of Pediatrics, University of California San Diego, 9500 Gilman Drive MC0828, La Jolla, CA 92093; California Preterm Birth Initiative, University of California San Francisco, San Francisco, CA. Electronic address: rjbaer@health.ucsd.edu.
2 Department of Pediatrics, University of California San Diego, La Jolla, CA.
3 California Preterm Birth Initiative, University of California San Francisco, San Francisco, CA; Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA.