[1] Inst Nacl Salud, Ctr Nacl Salud Publ, Lima 11, Peru
[2] Univ Peruana Ciencias Aplicadas, Escuela Med, Lima 11, Peru
[3] Hosp III EsSalud Cayetano Heredia, Dept Ginecol & Obstetricia, Piura, Peru
[4] Univ Nacl Piura, Fac Med Humana, Piura, Peru
[5] Minist Salud, Direcc Reg Salud Tumbes, Tumbes, Peru
[6] Univ Nacl Mayor San Marcos, Escuela Postgrado, Lima 14, Peru
[7] Univ Zaragoza, Fac Med, Hosp Clin, Dept Obstet & Ginecol, Zaragoza, Spain