[1] UCL Royal Free & Univ Coll Med Sch, Dept Child Hlth, Royal Free Hosp, London NW3 2PF, England
[2] Ctr Med Genet, Brussels, Belgium
[3] Sahlgrens Univ Hosp, Dept Obstet & Gynaecol, S-41345 Gothenburg, Sweden
[4] Copenhagen Univ Hosp, Fertil Clin, Rigshosp Sect 4071, Copenhagen, Denmark
[5] Geniki Klin, Infertil & IVF Ctr, Thessaloniki, Greece
[6] UCL Royal Free & Univ Coll Med Sch, Dept Primary Care & Populat Sci, London NW3 2PF, England
[7] Copenhagen Univ Hosp, Dept Growth & Reprod, Rigshosp Sect 5064, Copenhagen, Denmark
[8] UCL Royal Free & Univ Coll Med Sch, Dept Child Hlth, London, England