[1] Univ Birmingham, Div Reprod & Child Hlthl, Birmingham B15 2TT, W Midlands, England
[2] Univ Birmingham, Dept Pathol, Birmingham B15 2TT, W Midlands, England
[3] Univ Birmingham, Dept Med, Birmingham B15 2TT, W Midlands, England
[4] W Midlands Reg Clin Genet Serv, Birmingham, W Midlands, England
[5] St Marys Hosp, Dept Med Genet, Manchester, Lancs, England