[1] Univ Copenhagen, Dept Obstet, Ctr Fetal Med, Rigshosp, Blegdamsvej 9, DK-2100 Copenhagen, Denmark
[2] Res Ctr Prevent & Hlth, Registry Support Ctr East Epidemiol & Biostat, Glostrup, Denmark
[3] Aarhus Univ Hosp, Fetal Med Unit, Aarhus, Nord, Denmark