1. Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon, USA.
2. Portland State University, Portland, Oregon, USA.
3. Department Health Systems and Policy, OHSU-PSU School of Public Health, Portland, Oregon, USA.
4. Instituto Nacional de Salud Pública (INSP), Centro de Investigación en Salud Poblacional (CISP), Cuernavaca, Morelos, México.