[1] Univ Complutense Madrid, Sch Med, Dept Publ & Maternal & Child Hlth, Madrid 28040, Spain
[2] Univ Hosp Gregorio Maranon, Dept Obstet & Gynecol, Madrid 28009, Spain
[3] Hlth Res Inst Gregorio Maranon, Madrid 28009, Spain
[4] Univ Hosp Alvaro Cunqueiro, Dept Obstet & Gynecol, Vigo 36312, Spain
[5] Univ Hosp Alvaro Cunqueiro, Dept Surg, Vigo 36312, Spain
[6] Gregorio Maranon Hlth Res Inst IiSGM, Methodol & Biostat Unit, Madrid 28009, Spain
[7] Univ Alcala, Fac Med & Hlth Sci, Dept Med & Med Special, Alcala De Henares 28871, Spain
[8] Ramon y Cajal Inst Sanit Res IRYCIS, Madrid 28034, Spain