[1] Sorlandet Hosp HF, Dept Gynecol & Obstet, Egsveien 100, N-4615 Kristiansand, Norway
[2] Univ Bergen, Clin Inst 2, Med Dept, Haukelandsveien 28, N-5009 Bergen, Norway
[3] Univ Agder, Dept Hlth & Nursing Sci, Univ Veien 25, N-4630 Kristiansand, Norway
[4] Univ Agder, Dept Sport Sci & Phys Educ, Univ Veien 25, N-4630 Kristiansand, Norway