[1] Ostfold Hosp Trust, Dept Haematol, POB 300, N-1714 Kalnes, Norway
[2] Univ Oslo, Fac Med, Inst Clin Med, POB 1057, N-0316 Oslo, Norway
[3] Oslo Univ Hosp, Div Obstet & Gynaecol, Oslo, Norway
[4] Gothenburg Univ, Sahlgrenska Acad, Inst Clin Sci, Dept Obstet & Gynecol, Gothenburg, Sweden
[5] Oslo Univ Hosp, Oslo Ctr Biostat & Epidemiol, Oslo, Norway
[6] Oslo Univ Hosp, Div Paediat & Adolescent Med, Oslo, Norway
[7] Norwegian Inst Publ Hlth, Dept Chem Toxicol, Oslo, Norway
[8] Oslo Univ Hosp, Dept Neurol, Oslo, Norway
[9] Karolinska Univ Hosp, Astrid Lindgren Childrens Hosp, Stockholm, Sweden
[10] Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden
[11] Norwegian Univ Life Sci, Fac Chem Biotechnol & Food Sci, As, Norway
[12] Ostfold Hosp Trust, Genet Unit, Ctr Lab Med, Kalnes, Norway
[13] Norwegian Inst Publ Hlth, Dept Virol, Oslo, Norway