1 Women's Centre, John Radcliffe Hospital, Oxford, OX3 9DU, UK. Electronic address: margaret.rees@st-hildas.ox.ac.uk.
2 2nd Department of Obstetrics and Gynecology, Medical School, University of Athens, Aretaieio Hospital, 76 Vas. Sofias Str., GR 11528, Athens, Greece.
3 University of Valencia, 46010, Valencia, Spain.
4 Department of Clinical and Experimental Medicine, University of Pisa, Via Roma, 67, 56126, Pisa, Italy.