About the Authors

Gordon C. S Smith

To whom correspondence should be addressed. E-mail: gcss2@cam.ac.uk

Affiliation Department of Obstetrics and Gynaecology, Cambridge University, The Rosie Hospital, Cambridge, United Kingdom

Yolande Cordeaux

Affiliation Department of Obstetrics and Gynaecology, Cambridge University, The Rosie Hospital, Cambridge, United Kingdom

Ian R White

Affiliation Medical Research Council (MRC) Biostatistics Unit, Institute of Public Health, Cambridge, United Kingdom

Dharmintra Pasupathy

Affiliation Department of Obstetrics and Gynaecology, Cambridge University, The Rosie Hospital, Cambridge, United Kingdom

Hannah Missfelder-Lobos

Affiliation Department of Obstetrics and Gynaecology, Cambridge University, The Rosie Hospital, Cambridge, United Kingdom

Jill P Pell

Affiliation Department of Public Health, University of Glasgow, Glasgow, United Kingdom

D. Stephen Charnock-Jones

Affiliation Department of Obstetrics and Gynaecology, Cambridge University, The Rosie Hospital, Cambridge, United Kingdom

Michael Fleming

Affiliation Information and Statistics Division, National Health Service, Glasgow, United Kingdom

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

GCSS had full access to all of the data in the study, takes responsibility for the integrity of the data, the accuracy of the data analysis, and is the guarantor. GCSS formed the hypothesis. MF performed the linkage and extracted the population data. GCSS and IRW performed the statistical analysis. GCSS and YC designed the contractility studies. YC, DP, and HML recruited patients, conducted the contractility studies, and extracted data. GCSS drafted the paper. GCSS, YC, IRW, DP, HML, JPP, DSCJ, and MF critically reviewed the draft for content and approved the final version of the paper.