1. , 89 Southgate Road, London, N1 3JS, UK, Tel.: +44 (0)7710 065 164; Fax: +44 (0)20 7354 4708;
2. University Department of Obstetrics and Gynaecology, The Rosie Hospital, Robinson Way, Cambridge, CB2 2SW, UK. Tel.: +44 (0)1223 336 876; Fax: +44 (0)1223 215 327;
3. Research Institute Growth and Development, Department of Obstetrics and Gynaecology, University Hospital Maastricht, Peter Debyelaan 25, 6229 HX Maastricht, The Netherlands. Tel.: +31 (0)43 387 6625; Fax: +31 (0)43 387 6613;