1 School of Clinical and Experimental Medicine, Academic Department, University of Birmingham, Birmingham Women's Hospital, Birmingham B15 2TG, UK rima.dhillon@doctors.org.uk.
2 Institute of Applied Health Sciences, School of Medicine and Dentistry, Foresterhill, Aberdeen AB25 2ZD, UK.
3 School of Clinical and Experimental Medicine, Academic Department, University of Birmingham, Birmingham Women's Hospital, Birmingham B15 2TG, UK.
4 CARE (Centres for Assisted Reproduction) John Webster House, 6 Lawrence Drive, Nottingham Business Park, Nottingham NG8 6PZ, UK.
5 School of Health and Population Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.