[1] Univ Birmingham, Birmingham Womens Hosp, Dept Obstet & Gynaecol, Sch Clin & Expt Med, Birmingham B15 2TG, W Midlands, England
[2] Kleijnen Systemat Reviews Ltd, Westminster Business Ctr, York, N Yorkshire, England
[3] Univ Newcastle, Sch Surg & Reprod Sci, Newcastle, NSW 2308, Australia
[4] Maastricht Univ, CAPHRI, Sch Publ Hlth & Primary Care, Maastricht, Netherlands
[5] Hosp Ramon & Cajal, Clin Biostat Unit, E-28034 Madrid, Spain