Affiliation: | 1. Academic Department of Obstetrics and Gynaecology, University College London, Chenies Mews, London, UK;2. International Blood Group Reference Laboratory, Southmead Road, Bristol, UK;3. Fetal Medicine Unit, Elizabeth Garrett Anderson and Obstetric Hospital, University College London Hospitals, Huntley Street, London, and Clinical and Molecular Genetics, Institute of Child Health, 30 Guildford Street, London, UK |