1. Department of PediatricsUniversity of California San Diego La Jolla California
2. California Preterm Birth InitiativeUniversity of California San Francisco San Francisco California
3. Departments of Epidemiology and PediatricsUniversity of Iowa Iowa City Iowa
4. Department of Epi and BiostatsUniversity of California San Francisco San Francisco California
5. Department of ObstetricsGynecology and Reproductive Sciences, University of California San Francisco California