Footnotes

• Twitter @DrCBattersby, @NeenaModi1, @DrCGale

• Contributors JWHW, NM and CG conceived this project. JWHW, NL, SNU and CG planned the statistical analyses. Data were extracted from the NNRD by KO and checked by CB. Data analysis was undertaken by JWHW and NL. The first draft of the manuscript was written by JWHW and revised by CG. NL, CB, KO, SNU and NM edited and reviewed the manuscript. It was approved by JWHW, NL, CB, KO, SNU, NM and CG.

• Funding The NNRD is funded and maintained from awards to NM. These include costs for data transfer, storage, cleaning, merging, administration and regulatory approvals. The extraction of study data from the NNRD and analysis for this study was funded through a Mason Medical Research Fellowship awarded to JWHW. CG was funded by the UK Medical Research Council (MRC) through a Clinician Scientist Fellowship award.

• Disclaimer The MRC and Mason Medical Research Foundation were not involved in the design of the study, collection, analysis, and interpretation of data or in writing the manuscript.

• Competing interests JWHW has received support from Chiesi Pharmaceuticals to attend an educational conference and has received a research grant from Mason Medical Research Foundation. SNU has received funding from the National Institute of Health Research, the Department of Health and Prolacta Life Sciences. SNU has been on the Advisory Board of Fresenius Kabi and received honoraria and travel expenses for speaking at study days organised by Fresenius Kabi. SNU is a member of the National Institute for Health and Care Excellence Parenteral Nutrition Guideline Development Committee. NM is the Chief Investigator for the National Neonatal Research Database and Director of the Neonatal Data Analysis Unit at Imperial College London. In the last 5 years, NM has served on the Board of Trustees of the Royal College of Paediatrics and Child Health, David Harvey Trust, Medical Women’s Federation and Medact; and is a member of the Nestle Scientific Advisory Board. NM has received research grants from the British Heart Foundation, Medical Research Council, National Institute of Health Research, Westminster Research Fund, Collaboration for Leadership in Applied Health and Care Northwest London, Healthcare Quality Improvement Partnership, Bliss, Prolacta Life Sciences, Chiesi, Shire and HCA International; travel and accommodation expenses from Nutricia, Prolacta, Nestle and Chiesi; honoraria from Ferring Pharmaceuticals and Alexion Pharmaceuticals for contributions to expert advisory boards, and Chiesi for contributing to a lecture programme. CG is part of an international team developing reporting guidance (a CONSORT extension) for clinical trials using cohorts and routinely collected health data. He has received support from Chiesi Pharmaceuticals to attend an educational conference; in the past 5 years he has been an investigator on received research grants from Medical Research Council, National Institute of Health Research, Canadian Institute of Health Research, Department of Health in England, Mason Medical Research Foundation, Westminster Medical School Research Trust and Chiesi Pharmaceuticals, and has been an unremunerated member of the Neonatal Data Analysis Unit Board, which oversees the NNRD.

• Provenance and peer review Not commissioned; externally peer reviewed.

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