[1] Univ Manchester, St Marys Hosp, Acad Unit Child Hlth, Manchester M13 0JH, Lancs, England
[2] Univ Milan, Fac Med & Chirurg, Clin Ostetr & Ginecol, Milan, Italy
[3] Univ Turin, Dipartimento Discipline Ginecol & Ostetr, Turin, Italy
[4] Univ Hosp, Rhein Westfal TH Aachen, Dept Anat, Aachen, Germany
[5] Univ Milan, San Paolo Hosp, Sch Med, Dept Human Pathol, Milan, Italy
[6] Univ Oxford, John Radcliffe Hosp, Nuffield Dept Obstet & Gynaecol, Oxford OX3 9DU, England