About the Authors

Kathryn E. Fitzpatrick

Affiliation National Perinatal Epidemiology Unit, University of Oxford, Oxford, United Kingdom

Susan Sellers

Affiliation University Hospitals Bristol NHS Trust, Bristol, United Kingdom

Patsy Spark

Affiliation National Perinatal Epidemiology Unit, University of Oxford, Oxford, United Kingdom

Jennifer J. Kurinczuk

Affiliation National Perinatal Epidemiology Unit, University of Oxford, Oxford, United Kingdom

Peter Brocklehurst

Affiliation Institute for Women's Health, University College London, London, United Kingdom

Marian Knight

kate.fitzpatrick@npeu.ox.ac.uk

Affiliation National Perinatal Epidemiology Unit, University of Oxford, Oxford, United Kingdom

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: SS JJK PB MK. Analyzed the data: KF. Wrote the paper: KF. Contributed to the writing of the manuscript: SS PS JJK PB MK. Contributed to the analysis: JJK MK. Data coding and validation: KF PS.