- Correspondence to Dr Oliver Rivero-Arias, National Perinatal Epidemiology Unit (NPEU), Nuffield Department of Population Health, University of Oxford, Oxford OX3 7LF, UK;
- Received July 13, 2017
- Revised January 17, 2018
- Accepted January 18, 2018
- First published March 6, 2018.
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