[1] Queens Univ Belfast, Ctr Publ Hlth, Belfast, North Ireland
[2] St Georges Univ Hosp, Dept Genet, London, England
[3] Univ Tubingen, Dept Obstet & Gynecol, Tubingen, Germany
[4] Birmingham Womens & Childrens Fdn Trust, Fetal Med Ctr, Birmingham, England
[5] Univ Birmingham, Coll Med & Dent Sci, Birmingham, England
[6] Illumina, Med Genom Res Grp, Cambridge, England