1 University of Valencia, Pediatrics, Obstetrics and Gynecology, Av Blasco Ibañez 15, 46010 Valencia, Spain. Electronic address: antonio.cano@uv.es.
2 University of Pisa, Division of Obstetrics and Gynecology, Department of Clinical and Experimental Medicine, Via Roma, 67 Pisa, 56100 Pisa, Italy. Electronic address: tommaso.simoncini@med.unipi.it.
3 Women's Centre, John Radcliffe Hospital, Oxford OX3 9DU, UK. Electronic address: margaret.rees@st-hildas.ox.ac.uk.