1. Aragón Institute of Health Research (IIS Aragón), Obstetrics DepartmentHospital Clínico Universitario Lozano Blesa, Zaragoza Spain
2. Red de Salud Materno Infantil y del Desarrollo (SAMID), RETICS, Instituto de Salud Carlos III (ISCIII), Subdirección General de Evaluación y Fomento de la Investigación y Fondo Europeo de Desarrollo Regional (FEDER) Spain
3. Nuffield Department of Obstetrics and Gynaecology, Oxford Maternal and Perinatal Health Institute, Green Templeton CollegeUniversity of Oxford Oxford UK
4. Perinatology Research Branch, Program for Perinatal Research and Obstetrics, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services Bethesda MD and Detroit, MI USA
5. Department of Obstetrics and GynecologyWayne State University School of Medicine Detroit MI USA