[1] Univ Oslo, Inst Clin Med, Fac Med, Oslo, Norway
[2] Akershus Univ Hosp, Clin Paediat & Adolescence, Lorenskog, Norway
[3] Oslo Univ Hosp, Dept Neonatal Intens Care, Div Paediat & Adolescent Med, Oslo, Norway
[4] Univ Bergen, Dept Clin Sci, Bergen, Norway
[5] Haukeland Hosp, Dept Obstet & Gynaecol, Bergen, Norway
[6] Oslo Univ Hosp, Dept Fetal Med, Div Obstet & Gynaecol, Oslo, Norway
[7] Fac Med, POB 1078,Blindern, N-0316 Oslo, Norway