[1] Univ Bern, Fac Med, Bern, Switzerland
[2] Med & Serv GmbH Sachsen, Dept Stat Anal, Chemnitz, Germany
[3] Univ Hosp Bern, Inselspital, Dept Obstet & Gynaecol, Bern, Switzerland
[4] Univ Hosp Frankfurt, Dept Gynecol & Obstet, Div Gynaecol Endocrinol & Reprod Med, Frankfurt, Germany
[5] Univ Hosp Heidelberg, Dept Gynaecol Endocrinol & Fertil Disorders, Heidelberg, Germany
[6] Univ Hosp Inselspital, Dept Obstet & Gynaecol, Friedbuehlstr 19, CH-3010 Bern, Switzerland