[1] Norwegian Univ Sci & Technol, Fac Med & Hlth Sci, Dept Clin & Mol Med, Trondheim, Norway
[2] St Olavs Univ Hosp, Dept Obstet & Gynecol, Trondheim, Norway
[3] Norwegian Univ Sci & Technol, Fac Med & Hlth Sci, Dept Publ Hlth & Nursing, Trondheim, Norway
[4] Ostfold Hosp Trust, Dept Obstet & Gynecol, Gralum, Norway
[5] Oslo Metropolitan Univ, Fac Hlth Sci, Dept Nursing & Hlth Promot, Oslo, Norway
[6] St Olavs Univ Hosp, Dept Gynecol & Obstet, 3250 Torgarden, N-7006 Trondheim, Norway