1. Department of Obstetrics and Gynecology Akershus University Hospital Lørenskog Norway
2. Institute of Clinical Medicine University of Oslo Oslo Norway
3. Department of Diagnostic Imaging Akershus University Hospital Lørenskog Norway
4. Maternal and Fetal Health Research Centre Institute of Human Development University of Manchester Manchester UK
5. Saint Mary's HospitalManchester University Hospitals NHS Foundation TrustManchester Academic Health Science Centre Manchester UK