1. Department of Obstetrics and Gynecology. Universidad Nacional Mayor de San Marcos, Lima, Peru
2. Department of Obstetrics and Gynecology. Instituto Nacional Materno Infantil, Lima, Peru
3. Department of Obstetrics and Gynecology. Universidad Peruana Cayetano Heredia, Lima, Peru
4. Department of Obstetrics and Gynecology. Division of Maternal Fetal Medicine. University of Texas Medical Branch, Texas, United States