1. University of Leeds; Centre for Epidemiology and Biostatistics; Bradford Institute for Health Research Bradford Royal Infirmary, Duckworth Lane Bradford West Yorkshire UK BD9 6RJ
2. Queen Elizabeth II Research Institute; NSW Centre for Perinatal Health Services Research; Building DO2 University of Sydney Sydney NSW Australia 2006
3. The University of Liverpool; School of Reproductive and Developmental Medicine, Division of Perinatal and Reproductive Medicine; First Floor, Liverpool Women's NHS Foundation Trust Crown Street Liverpool UK L8 7SS
4. Royal Women's Hospital; Department of Perinatal Medicine; Carlton Victoria Australia 3053